United States
Department of
Agriculture
Animal and
Plant Health
Inspection
Service
A Pathway Assessment of the Risk of
Establishment in the Contiguous United
States by Copitarsia decolora (Guenée) on
Asparagus from Peru
Juli R. Gould1, Barney P. Caton2, Robert C. Venette3
June 2006
1
USDA-APHIS-PPQ
Center for Plant Health Science and Technology
Pest Survey, Detection, and Exclusion Laboratory
Otis ANGB, MA
2
USDA-APHIS-PPQ
Center for Plant Health Science and Technology
Plant Epidemiology and Risk Analysis Laboratory
Raleigh, NC
3
North Central Research Station
U.S. Forest Service
St. Paul, MN
Copitarsia decolora (Guenée) on Asparagus from Peru
EXECUTIVE SUMMARY
Copitarsia decolora is a noctuid moth that is found in Central and South America. Eggs and
larvae of this insect are often intercepted on imported produce and cut flowers at United States
ports of entry. Peruvian asparagus was so frequently infested that all shipments now require
treatment with pesticides prior to importation. A 2000 risk assessment concluded that the risks
associated with this potential pest were probably high, but the quality and availability of data
used to reach that conclusion were inadequate. A project was undertaken to collect the data
necessary to produce an accurate science-based risk assessment to either validate or refute the
need for high vigilance and expensive treatments. We describe a pathway analysis starting with
the shipment of asparagus from Peru to the United States and determine the effects of
environmental conditions and procedures followed at importer, wholesale, and retail facilities on
the survival and establishment of immature C. decolora.
Probabilistic models were constructed to estimate the risk of C. decolora escaping into the wild
from importer, wholesale, or retail facilities. For this insect to escape, larvae must hatch from
eggs and be able to crawl into the environment. Because of the cold temperatures at which
asparagus is shipped to preserve freshness and the short time from harvest to consumption, a
very small percentage of eggs have an opportunity to escape. This opportunity comes when
asparagus spears with C. decolora eggs are discarded into a dumpster. Given the large volume
of asparagus from Peru, a few insects might be able to exploit this possibility. Several
information sources were consulted and new information was gathered to estimate the chances
that one or more female larvae and at least one male (with whom she could mate) might escape.
The number of potential mated females was also calculated. Information was obtained from the
Foreign Agricultural Service database regarding the amount of green asparagus imported
monthly from Peru. Separate models were constructed for three seasons because eighty percent
of fresh asparagus is imported from Peru during September-December and much less asparagus
is imported from February to May. The number of eggs per spear was determined from data
collected by Peruvian cooperators. The amount of asparagus discarded in dumpsters was
determined by surveying importers, wholesalers, and retailers. Known infested asparagus was
shipped to the United States, following strict biosecurity procedures, to determine how many
eggs were still viable and how soon eggs might hatch. A study in Peru measured percentage of
newly hatched larvae that could crawl out of a garbage receptacle filled with asparagus. Climate
models were used to predict where the climate is potentially suitable for population
establishment. Because data do not exist on availability of host plants, larval survival, or mate
finding, these parameters were not included in the model. The model is therefore conservative in
the estimate of risk.
The probability that at least one potential mated female could escape from the asparagus pathway
at one or more importer facilities approached 100 percent and the average time to the first
potential mated female was 1 year for all three seasons. The number of potential mated females
escaping at a single facility was greatest during September-December (average = 37), however
even during the least risky season (February-May) the model predicted an average of 5 females,
and as many as 70, per facility. Clearly the risk was greatest during the September to December
time frame, when most of the asparagus from Peru is imported, but the risk remained high during
the other periods. The model estimated that a potential mated females could escape from a
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Copitarsia decolora (Guenée) on Asparagus from Peru
wholesale facility in four years during September-December, but the maximum number of
potential mated females at a single facility averaged less than one and did not exceed three.
During Jan/Jun-Aug and Feb-May, the numbers of years to the first potential mated female were
20 and 82; again with an average of less than one potential mated female escaping the produce
pathway when females did escape. The model did not predict that any potential mated females
would be produced at individual retail facilities.
The probabilistic model indicated that the risk of at least one female and male C. decolora larva
escaping into the wild was greatest at importer facilities and during the September to December
time frame. While escape at importer facilities is most likely to occur on imports during the
period from September to December, the differences between that and the other time periods did
not seem to justify seasonal differences in handling and disposal of asparagus. Asparagus from
Peru enters the U.S. through two ports: Miami and Los Angeles. The climate modeling software
CLIMEX strongly indicated that the Los Angeles area was climatically very suitable for
establishment. Miami may be climatically suitable for establishment, but we are uncertain about
that classification. Regardless, from both pathway and climate modeling, we conclude that the
risk of establishment by C. decolora is greatest for asparagus discarded by importers in the Los
Angeles area. Establishment is less likely but possible on discards by importers in the Miami
area. Escape of potential C. decolora mated females is even less likely from asparagus discarded
by wholesalers anywhere, especially during the transitional and Feb-May time periods, and even
less probable at retailer’s facilities.
Efforts are being made to reduce the number of C. decolora eggs per asparagus spear in Peru.
Simulations were run using egg densities 10, 100, and 1000-fold lower than those used in this
study. The effect on potential risk of lowering egg density, moving importer facilities, and
requiring disposal methods other than discarding in dumpsters are discussed.
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Copitarsia decolora (Guenée) on Asparagus from Peru
Table of contents
EXECUTIVE SUMMARY ............................................................................................................ 2
I. INTRODUCTION ....................................................................................................................... 1
II. DATA COLLECTION AND MODEL DEVELOPMENT ....................................................... 2
A. Surveys of importers, wholesalers, and retailers.................................................................... 2
1. Importers ............................................................................................................................. 3
2. Wholesalers......................................................................................................................... 3
3. Supermarkets....................................................................................................................... 3
B. Probabilistic Modeling ........................................................................................................... 4
1. Simulation settings.............................................................................................................. 5
2. Importer model.................................................................................................................... 4
3. Wholesaler model ............................................................................................................. 15
4. Retailer model ................................................................................................................... 18
5. Simulation of Reduced Egg Density................................................................................. 18
6. Climate Model .................................................................................................................. 19
III. RESULTS AND DISCUSSION ............................................................................................. 24
A. Probabilistic modeling ......................................................................................................... 24
1. Importers ........................................................................................................................... 24
2. Wholesalers....................................................................................................................... 26
3. Retailers ............................................................................................................................ 28
4. Simulating reductions in egg densities ............................................................................. 28
B. CLIMEX modeling .............................................................................................................. 30
IV. CONCLUSIONS .................................................................................................................... 33
A. Current risk .......................................................................................................................... 33
B. Risk mitigation possibilities ................................................................................................. 34
V. References................................................................................................................................ 35
Appendix A. Letter sent to randomly selected wholesale facilities.............................................. 37
Appendix B. Survey sent to randomly selected wholesale facilities. ........................................... 38
Appendix C. Survey sent to supermarket facilities. .............................................................. 40
Appendix C. Survey sent to supermarket facilities. .............................................................. 40
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Copitarsia decolora (Guenée) on Asparagus from Peru
I. INTRODUCTION
Eggs and larvae of insects in the genus Copitarsia (Hampson) are frequently intercepted in the
United States at ports of entry (USDA-APHIS-PPQ, 2005). Between January 1985 and April
2000, 7,434 interceptions of Copitarsia sp. entering the United States were reported, with 4,617
of those at the port of Miami alone. Because these insects are considered actionable pests
(species for which APHIS has the authority to require treatment before entry (USDA-APHISPPQ 2006) and they are so frequently intercepted, certain commodities from South and Central
America must be treated with pesticides before leaving a port of entry because of the presence of
Copitarsia spp. In the absence of any regulatory controls, the possibility of damage from
Copitarsia spp. seems great: evidence exists that they feed on 50 crop plants in 19 plant families.
However, recent assessments of pest risk for Copitarsia moths (Gould et al. 2000, Venette and
Gould 2006) suggested that while the risks of introduction, establishment, and economic damage
were probably high, the availability or quality of the data were not adequate to address many key
risk assessment elements with confidence. Although border officers spend considerable time and
resources on the detection and treatment of Copitarsia species, the risk has not been adequately
assessed.
The goal of this project was to collect the data necessary to produce an accurate science-based
risk assessment to either validate or refute the need for high vigilance and expensive treatments.
An additional goal was to identify those portions of the pathway that were most risky so that
mitigation measures could be identified. We were able to describe the risk posed by a single
species, C. decolora, rather than the entire genus as in Gould et al. (2000), because of advances
in our knowledge of the taxonomy of the genus (Simmons and Pogue 2004, Simmons and
Scheffer 2004). The pathway followed by C. decolora on asparagus from Peru was chosen
because taxonomic analysis of Copitarsia larvae intercepted at ports in Texas and Florida
indicated that only C. decolora arrives on imported commodities (R. Simmons pers. comm.) and
all asparagus currently imported from Peru must be fumigated because of the perceived threat
from C. decolora.
For the purpose of pest risk assessment, risk is defined as the probability of an exotic pest
becoming established weighted by the consequences of establishment (Orr et al. 1993). In the
2000 risk assessment of the genus Copitarsia (Gould et al. 2000), a panel of experts gave high
risk ratings to risk elements that concerned the consequences of establishment and expressed
high confidence in these ratings. For elements concerning the probability of establishment, the
risk ratings were more variable and the confidence expressed in these ratings was lower. This
study was designed to collect data and perform analyses to address the probability of
establishment.
To successfully establish in the United States, C. decolora arriving on asparagus from Peru must
survive shipping conditions and find an environment suitable for survival, reproduction, and
population growth. More specifically, a significant number of individuals would have to:
1. Survive the environmental conditions of shipment
2. Escape from the produce pathway
3. Locate a suitable host plant
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Copitarsia decolora (Guenée) on Asparagus from Peru
4. Survive to the adult stage
5. Find a mate
6. Create a self-sustaining population
The fate of imported commodities can have a profound impact on the probability of
establishment, especially for a solitary, sexually reproducing organism like C. decolora that are
typically imported as eggs. Even when climatic conditions are favorable and host plants are
available, the probability of establishment will be low if organisms cannot survive shipment or
are unlikely to escape from the shipment pathway.
We describe a pathway analysis starting with the shipment of asparagus from Peru to the United
States and determine the effects of environmental conditions and procedures followed at
importer, wholesale, and retail facilities on the survival and establishment of immature C.
decolora. We researched and modeled steps (1) and (2) above; the data needed to model steps (3)
through (6) remain unavailable. Still, characterizing and better quantifying our understanding of
the pathway up through step (2) represents a significant advance from the previous risk
assessment. In addition, climate modeling is used to evaluate whether larvae that escape from the
produce pathway would find an environment suitable for continued survival and reproduction.
Collecting data to verify the conclusions of a risk assessment has many benefits. If an updated
risk assessment concludes risks are low, then the limited resources currently spent searching for
and fumigating the pest can be spent inspecting commodities of higher risk. If the risk of the pest
is confirmed to be high, the data collected during the risk assessment process will be invaluable
to scientists designing detection, control, and/or eradication programs, should the pest become
established. Either way, American agriculture benefits from the process of data collection and
analysis. This study demonstrates how collecting biological data can enhance the risk assessment
process for pests of perishable, consumable commodities.
II. DATA COLLECTION AND MODEL DEVELOPMENT
A. Surveys of importers, wholesalers, and retailers
How asparagus is treated during and after shipment has great effects on the risk of establishment
by C. decolora. The insects cannot hatch if temperatures remain below the threshold for
development. Also, certain outcomes logically constitute a very low risk of producing a self
sustaining population, for example eggs or larvae on asparagus that are consumed, rot in a
vegetable drawer, or go through a trash compactor. We have assumed that C. decolora on
asparagus eaten by consumers poses no risk. Similarly, C. decolora on asparagus that is crushed
in a trash compactor, ground in a garbage disposal, or buried in a landfill cannot survive to
adulthood. To determine final fates of imported asparagus we surveyed asparagus importers,
wholesale produce distributors, and retailers (supermarkets). The survey was done by a
contractor, Corporate Resource Inc., with expertise in produce marketing. The methodology is
described below. The results of the surveys are provided in subsequent sections.
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Copitarsia decolora (Guenée) on Asparagus from Peru
1. Importers
In October, 2003, Corporate Resource Inc. distributed a survey to the members of the Peruvian
Asparagus Importers Association at the Produce Marketing Association Meeting in Florida.
Fourteen of 25 asparagus importers, accounting for approximately 90 percent of asparagus
imports from Peru, completed the questionnaire.
Importers reported the amount of asparagus imported during the previous year, the amount or
percentage discarded and the method used, and how often garbage was removed from the
premises. Information on minimum, target, and maximum time and temperature of storage at the
warehouse were reported. Importers and wholesalers also provided information about target
customers: other wholesalers, restaurants, or grocery stores (retailers).
2. Wholesalers
Corporate Resource Inc. also surveyed wholesale produce distributors by sending them a cover
letter (Appendix A) and a survey form (Appendix B). The questions were similar to those asked
of importers. We randomly selected 350 wholesalers from the 7,768 warehouses listed in the
Perishable Agriculture Commodities Act (PACA) database (USDA-Food and Nutrition
Services). We received 12 responses (or only 3.4 percent). We sent each wholesaler a survey
again and received another 6; for a total of 18 or 5 percent.
3. Supermarkets
The first attempt to collect data about garbage disposal procedures at supermarkets was done by
mailing 500 surveys to supermarkets throughout the United States. The database used to select
stores to contact was the USDA list of the 145,916 companies that accept food stamps (USDAFood and Nutrition Service). The categories of stores as listed in the database were COMB GRO
& MERCH (e.g. Big K-Mart, Walmart Superstore), CONVENIENCE (e.g. 7-11, Mobile on the
Run, etc.), COMB GRO & GAS, SUPERMARKETS, SPECIALTY FOOD, SMALL/MEDIUM,
PRODUCE STAND (probably selling American grown produce), GROUP LIVING ARRG, and
OTHER COMBINATION. Obviously many of the facilities that accept food stamps would not
sell produce, and we did not include those categories. We assumed that the SUPERMARKETS
category, comprised of 33,002 entries, would handle the majority of the produce sold in the
United States and these were selected to survey.
The surveys (Appendix C) were mailed to 500 randomly selected supermarkets in January, 2004,
but the response rate was low (1.2%). Instead of resending the survey, we decided on a more
targeted approach. Because preliminary climate modeling indicated that C. decolora was most
likely to establish in coastal California, we selectively surveyed supermarkets there. Produce
disposal procedures and food storage protocols were found to be largely standard throughout
facilities managed by each supermarket chain. Consequently, surveys were completed by
corporate produce managers for the seven largest chains, operating a total of 1,784 grocery
stores. We also included in our analysis the data from the six independent grocery stores that
completed the survey.
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Copitarsia decolora (Guenée) on Asparagus from Peru
B. Probabilistic Modeling
The models developed predict the likelihood of at least one female and one male escaping from
the produce pathway at the same location and within a time-frame (two weeks) in which they
could survive long enough to locate each other and mate. For this model we define potential
mated females as female larvae leaving a dumpster in which asparagus had been discarded along
with at least one male with which they could mate. Separate estimations were done for three
seasons when different quantities of asparagus were imported from Peru. The models predict the
number of years until a potential mated female would be seen at any of the facilities nationwide,
as well as the number of potential mated females that could be expected at a single facility. Many
events must occur after C. decolora larvae leave the dumpster for a population to establish:
finding host plants, avoiding predators, finding a mate, ovipositing, etc. Because data on those
processes were not available we excluded them from the analysis. The model is, therefore, very
conservative in estimating the risk of obtaining a reproducing population (i.e., it overestimates
the risk of population establishment). Figure 1 shows an overall diagram of the movement of
asparagus through and out of the importation pathway.
1. Simulation settings
All models were spreadsheets run using the Microsoft Excel add-in @Risk (ver. 4.5.0
Professional, Palisades Corporation, 31 Decker Road, Newfield, NY 14867). Unless otherwise
specified, simulation settings were as follows: number of iterations = 10,000; sampling type =
Latin Hypercube; and random seed = 1.
2. Importer model
a. Amount of asparagus imported from Peru to the United States
Asparagus imports may be fresh, frozen, or otherwise preserved. We only included imports of
fresh green asparagus, because the white and processed asparagus do not harbor viable C.
decolora eggs. Import data were from the USDA Foreign Agricultural Service HS 10-digit
Imports database (USDA-FAS 2006). We queried for data on green asparagus (fresh or chilled)
from Peru.
Annual imports of asparagus from Peru have been increasing since 1998, reaching 130 million
pounds in 2005 (USDA-FAS 2006). However, the rate of increase has slowed considerably in
recent years (Fig. 2), so the analysis concentrated on the amount of asparagus imported from
2003 through 2005. We believe this reflects the latest trend in asparagus imports. The number of
pounds imported fit a linear regression (F = 69.7, p =0.07, R2 = 0.99). Using the 95 percent
prediction limits from that regression for the year 2006, we modeled the amount imported
annually, A (pounds per year), as follows:
A = Pert(Amin, Aml, Amax) = (111,297,080; 136,398,052; 161,499,023)
[1]
where Amin is the minimum possible value, Aml is the most likely value, and Amax is the maximum
value possible. Pert distributions are curvilinear and usually represent tails and shoulders of data
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Copitarsia decolora (Guenée) on Asparagus from Peru
Annual imports of
Peruvian asparagus (lbs.)
Proportion imported during each season
Pounds asparagus
at importers per season
S1
S2
S3
Proportion asparagus
discarded by importers
Pounds discarded
by importers by season
Pounds asparagus
to wholesalers
S1
S2
S3
Proportion discarded
by wholesalers
Pounds discarded
by wholesalers by season
Proportion sent
to restaurants
Pounds to restaurants
Pounds asparagus
to retailers
S1
S2
S3
Proportion discarded
by retailers
Pounds discarded
by retailers by season
Pounds to consumers
Figure 1. Flow diagram of asparagus imported to the United States from Peru. Boxes are
estimated variables and arrows are probabilities.
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Copitarsia decolora (Guenée) on Asparagus from Peru
better than triangular distributions (Vose 2000). We used a one-year projection for simplicity. If
imports of asparagus from Peru continue to increase over time, the estimated amounts in the
model would be low, and results would probably underestimate the true risk. Recent percentage
increases have been declining (Fig. 2), however, so our approach seems reasonable.
Seasonally, the amount of asparagus imported increases starting in June and peaks in November
(Fig. 3). We modeled the risk of establishment for three time periods: 1) September to
December, when import volumes were greatest; 2) January plus June to August, when volumes
were moderate and increasing or decreasing; and 3) February to May, when volumes were least.
The amount imported during those periods, As (pounds per season), was the product of A and the
proportion imported during that season, Props, where s is the season. Values for Props were
predicted from the empirical data for 2000-2005
(http://www.fas.usda.gov/ustrade/USTImHS10.asp?QI=). The proportion of asparagus imported
in Sept-Dec. ranged from 0.61 to 0.70, the proportion ranged from 0.23 to 0.30 for the
intermediate period, and the range was 0.06 to 0.09 for the Feb-May period. Two seasons were
predicted as follows:
Props = uniform(mins,maxs)
[2]
where mins is the minimum proportion for the period, maxs is the maximum, and uniform
indicates a distribution in which all values between min and max are equally likely. The third
value was simply 1 – (Prop1 + Prop2). In all calculations below, we generated separate estimates
for each of the three time periods.
b. Amounts of Peruvian asparagus imported and discarded per importer
In total, the importers surveyed sold 144,650,011 lb. of asparagus during 2003 and discarded
2,388,394 lb., or 1.6 percent (Table 1). Some of the asparagus they handled came from countries
other than Peru, but we assumed that each importer imported and discarded the same proportion
of the total Peruvian asparagus as the proportion of the overall import total. Thirteen of the 14
companies surveyed imported 90 percent of the asparagus entering the United States from Peru
(Peruvian Asparagus Importers Association personal communication). We assumed that those
importers consistently accounted for 90 percent of the imports and that other importers
accounted for the rest. We allowed for uncertainty by predicting the amount going to the group
of 13 (As,G13; pounds per season) in a binomial process. The binomial function (e.g. Vose 2000)
returns the number of successes (S) for n independent trials, each with a constant probability of
success, p, for that iteration, as follows:
S = binomial(n, p)
[3]
In this case, p was estimated as the proportion imported by the group of 13 importers (PropG13 =
0.9). Typically, this is predicted as in Eqn. (3), but in Excel that function only operates if n <
32,000. Because amounts here were in the hundreds of millions, we used the normal
approximation of the binomial as follows (e.g., Vose, 2000):
AsG13 = normal(np, np (1 − p )
[4]
[5]
= normal( As x PropG13, ( As x PropG13 x (1 - PropG13) )
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Copitarsia decolora (Guenée) on Asparagus from Peru
60
Percentage Increase
50
40
30
20
10
0
1998
1999
2000
2001
2002
2003
2004
2005
2006
Year
Figure 2. Percentage increase in asparagus imports from Peru to the United States compared
with the previous year. (Department of Commerce, United States Census Bureau, Foreign Trade
Statistics)
Figure 3. Quantities of asparagus imported to the United States from Peru by month.
(Department of Commerce, United States Census Bureau, Foreign Trade Statistics)
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Copitarsia decolora (Guenée) on Asparagus from Peru
Because the quantity of asparagus discarded at individual facilities effects risk and we had that
information, we tracked the amounts for each importer, and the associated risks, separately. This
was a binomial process that depended on As and the proportion received by each importer, PropI
(where I = 1 to 13), as reported in the survey. The amounts going to each importer by season,
As,I, were binomial processes (Eqn. (3) or (4)), but because their sum had to equal As, we used a
multinomial process which adjusts for the amounts and probabilities remaining as values are
sequentially assigned, assuring that the exact amount is apportioned (not shown; e.g. Vose,
2003). A flow chart showing the steps modeled for asparagus discarded at importer facilities is
shown in Figure 4. The same steps were modeled for the wholesale and retail facilities.
c. Amounts of asparagus discarded in dumpsters
Only discarded asparagus poses any risk at the importer facilities because fresh asparagus for
sale is kept below 6ºC, which is below the threshold (7.8ºC) for egg hatch (Gould et al. 2005).
Importers discarded from 0 to 5 percent of the asparagus that came through their warehouses
(Table 1). We sampled the proportion of the total discarded by each importer in a discrete
function, which was determined from observed values and the probability associated with each
(i.e., n/ntot). The total amounts discarded at each importer, Ds,I, were the product of the
proportion discarded and As,I.
Importers discard asparagus using one of five methods: trash compactor, bagged in plastic, put
into a garbage disposal, given to a soup kitchen, or put (unbagged) into a dumpster. We only
consider unbagged asparagus that goes into a dumpster to present a risk for C. decolora
establishment. Because trash compactors and garbage disposals crush and grind the product we
assumed that C. decolora eggs are destroyed along with the produce. In addition, bagged
asparagus quickly rots, and in laboratory and field experiments no C. decolora survived to the
pupal stage on rotten asparagus (Gould and Huamán 2006). Eggs also will not survive if they are
cooked and consumed at a soup kitchen. Half of the importers used more than one method of
disposal; we assumed that each was used with equal frequency.
Overall, 76 percent of discarded asparagus was put into dumpsters, but the probability of
discarding into a dumpster varied by importer. Some discarded all asparagus by that method (p =
1) and some none (p = 0). The proportions discarded were quantified from the survey results. We
assumed that those probabilities did not vary by season. The amount discarded into the dumpster,
DDs,I, by each importer per season was a binomial process (Eqns. (3) or (4)) that depended on p
and Ds,I.
d. Number of spears discarded
Estimating the number of spears discarded requires converting from pounds to spears. Each
bunch of asparagus weighs approximately one pound, so the number of pounds and bunches are
about the same. The number of spears per bunch was estimated by counting the number of spears
in 705 bunches of asparagus that arrived from Peru at the port of Miami in November 2003. Five
5-kg boxes were randomly selected from each arriving consignment (packing shed) each day.
One bunch was selected at random from each box and the number of spears was counted.
Bunches had from 6 to 100 spears, with a mean of 30.3 (Figure 5). We fit a function to the data
in @Risk, and the best fitting distribution was a negative binomial with two parameters, s = 5,
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Copitarsia decolora (Guenée) on Asparagus from Peru
and p = 0.142. In addition, we set a minimum value equal to the observed value of 6 (i.e., no
values < 6).
Table 1. Annual amounts of asparagus imported and discarded by importers surveyed in 2003.
Importer Imported (lbs) Discarded (lbs) Percentage discarded (%)
1
8,000,000
247,423
3.0
2
6,000,000
0
0.0
3
14,000,000
50,000
0.4
4
2,000,000
0
0.0
5
60,000,011
1,224,490
2.0
6
400,000
0
0.0
7
3,850,000
78,571
2.0
8
4,400,000
4,400
0.1
9
3,500,000
53,299
1.5
10
10,000,000
526,316
5.0
11
11,000,000
111,111
1.0
12
15,000,000
0
0.0
13
3,500,000
0
0.0
14
3,000,000
92,784
3.0
144,650,011
2,388,394
Average = 1.6
Total
At this point, we converted seasonal values to values over two weeks by dividing by eight.
Copitarsia decolora adults live for slightly over three weeks at temperatures above 20ºC (Gould
et al. 2005). They probably do not live that long in the field, and egg laying only occurred over a
17 day period. Although we did not watch mating in the laboratory studies, all females began
laying eggs after a pre-oviposition period of three to five days. Even females that did not mate,
as evidenced by infertile eggs, began laying eggs by 7 days after eclosion. Unmated females laid
only half as many eggs as mated females, but they still laid an average of 601 eggs. These
findings suggest that C. decolora females are receptive to mating during the first week posteclosion, but we conservatively assumed that a male and a female that emerged within two
weeks of each other at the same location could potentially find each other and mate.
e. Number of eggs per two week period
The number of eggs per two weeks depended upon the total number of spears, Nsprs, and the
number of eggs per spear. A packing shed in Pisco, Peru had excellent data for C. decolora eggs
per spear. The data were collected from August, 2001, to January, 2002, as required by the
Ministry of Agriculture. That time period is particularly appropriate because 80 percent of
asparagus imports from Peru arrive during those months. Workers sampled 200 or more spears
per farm per day, and sampled more than 1 million spears total. Almost 99 percent of the spears
had no eggs (Table 2), and the mean number of eggs per spear, x eggs, was 0.0113 (SDeggs =
0.118), or one egg per 88 spears.
The number of eggs per two weeks, Neggs, was estimated using the Central Limit Theorem, as
follows (Vose, 2000):
Neggs = normal( Nsprs x x eggs, ( Nsprs x SDeggs)
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[6]
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Copitarsia decolora (Guenée) on Asparagus from Peru
Asparagus discarded
Pounds discarded per importer per season
Probability of discarding in a dumpster
Amount in dumpster
Pounds discarded in dumpster per importer per season
Number of spears per bunch
No. spears discarded per importer per two weeks
Spears discarded
Number of eggs per two weeks
No. C. decoloraeggs discarded per importer per two weeks
Eggs
Proportion ofC. decoloraeggs that are viable
Viable eggs
No. viable eggs per importer per two weeks
Probability of larvae staying long enough before garbage pick up
Eggs remain 2+ days
No. eggs not taken to landfill before hatch
Probability of egg hatch
Larvae hatching
No. hatched larvae
Probability of larvae crawling out of dumpster
No. larvae escaping
Larvae escaping dumpster
Probability ofC. decolora potential mated females
Potential mated females
No. of potential mated females
Probability of potential mated females nationwide annually
Yrs to 1st potential mated female
Years until first potential mated female leaves dumpster
during season
Figure 4. Flow diagram showing the fate of C. decolora eggs that are discarded at importer
facilities. Boxes are estimated variables and arrows are probabilities.
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10
Frequency
Copitarsia decolora (Guenée) on Asparagus from Peru
30
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
6
11
16
21
26
31
36
41
46
51
56
61
66
71
76
81
86
91
96
Number of Spears
Figure 5. Number of spears per bunch of asparagus imported from Peru to Miami in November
2003 (n=705).
This Central Limit Theorem function estimates the variation in the sum of a large number of
independent samples. In other words, Eqn. (6) substitutes for the cumbersome procedure of
sampling Nsprs separate values from normal( x eggs, SDeggs).
Table 2. Numbers of C. decolora eggs per asparagus spear at a packing shed in Pisco, Peru from
August 2001 to January 2002.
Eggs (no.) Frequency Percentage of total (%)
0
1,019,637
98.87
1
10,004
0.97
2
1,310
0.13
3
201
0.02
4
57
0.006
5
22
0.002
6
10
0.001
7
3
<0.001
8
16
0.002
9
2
<0.001
10
4
<0.001
11-19
11
0.001
20-29
5
0.001
30+ 1
4
<0.001
1,031,286
Total
1
The maximum number of eggs found on one spear was 37
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Copitarsia decolora (Guenée) on Asparagus from Peru
f. Number of potentially viable eggs
To determine survival of C. decolora eggs on asparagus from Peru, eggs were shipped to the
USDA-APHIS laboratory in Massachusetts via the standard pathway. In Peru in January, 2003
we marked the locations of eggs on asparagus spears; our goal was to send boxes of approx. 220
spears known to contain eggs from three packing sheds. Spears were bunched and boxed for
shipment as normal. To satisfy United States quarantine requirements for unfumigated C.
decolora eggs, organdy (a fine white mesh fabric) was placed over the holes in the box, and the
box was sewn into a large organdy sleeve. Boxes were refrigerated, taken to a storage facility in
Lima (Frio Aereo), shipped by airplane to Miami, and taken by refrigerated truck (courtesy of
Alpine Marketing) to the USDA-APHIS quarantine facility in Massachusetts. The proportions of
eggs that were potentially viable (i.e. eggs that were not black or had collapsed) were recorded
(Table 3).
Table 3. Proportion of C. decolora eggs hatching after shipment from Peru to the United States
through typical shipping channels. Some eggs were reared at 15 ºC to determine how many
degree days were required for hatching.
Shed Eggs at arrival Survival rate Incubated eggs Hatched eggs Proportion hatching
(no.)
(no.)
(no.)
Total Not viable
15 °C 22 °C 15 °C 22 °C 15 °C
22 °C
1
243
30
0.88
164
49
128
43
0.78
0.88
2
205
37
0.82
127
41
66
26
0.52
0.63
3
93
6
0.94
24
63
13
40
0.54
0.63
g. Accumulation of degree days by eggs in Peru
Copitarsia decolora eggs accumulate some degree days while still in the field in Peru, but then
are kept below 6 ºC, which is below the temperature threshold for development (7.8 ºC) (Gould
et al. 2005). Heat units are not, therefore, accumulated during shipment in refrigerated
containers. Sometime after arrival in the U.S, though, they will again experience temperatures
favorable for egg development. How quickly eggs hatch will depend in part on how many degree
days were accumulated in Peru.
We empirically estimated the number of degree days accumulated by C. decolora eggs in Peru.
The study was done in January, which is mid-summer in Peru, under the assumption that
development in the field would be maximal then. Copitarsia decolora eggs were shipped to the
United States as described in the survivorship trial above. Copitarsia decolora eggs have a base
temperature for development of 7.8 °C and require 69.1 degree days for hatching (Gould et al.
2005). Therefore, assuming no development during cold shipment, the difference between 69.1
degree days and the number of additional degree days needed in the laboratory for hatching
would estimate the number of degree-days accumulated in Peru. Individual eggs and
approximately 3 cm of asparagus spear were placed in closed 60 ml cups and then into a growth
chamber with an average temperature of 15 °C. We checked the eggs once per day and recorded
the number hatched. We chose to hatch some of the eggs at 15 °C because we were only
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Copitarsia decolora (Guenée) on Asparagus from Peru
recording hatch once daily and hatch would be more prolonged at the cooler temperatures, giving
us more precision in our estimates.
Most eggs (84%) required between 55 and 69 degree days to hatch, or from 80 to 100 percent of
the total (Fig. 6). Therefore, most eggs accumulated only 0 to 20 percent of the required degree
days for hatching while in Peru.
80
Frequency
60
40
20
0
40
50
60
70
80
90
100
110
Percentage of Degree-Days Still Required for Hatch
Figure 6. The percentage of the total degree-days required for hatching of C. decolora eggs after
arrival in the United States
h. Number of eggs not sent to a landfill before hatch
When asparagus containing C. decolora eggs enters a landfill it may be covered with more trash
and at least 0.3 m (12 inches) of soil within one day, according to regulations (EPA, 1993).
Ultimately it is covered with at least several meters of material, and perhaps dozens of meters if
placed low in the mound. Laboratory and field studies confirmed only low survival, 6.7 percent,
of C. decolora on dry discarded asparagus, and 0 percent survival on rotted asparagus, even if
uncovered (Gould and Huamán 2006). Given these factors, we consider any asparagus that is
sent to the landfill to present very low risk. It is during the period after asparagus is discarded in
the dumpster and prior to trash pickup that the larvae can crawl out of the dumpster and escape
from the produce pathway.
Asparagus importers indicated the number of times per week garbage was picked up at their
facilities. Importers have facilities in either Los Angeles, CA, or Miami, FL. Because the eggs
still need about 80 percent of the required degree days to hatch, under normal temperature
conditions in these locations, we expect that C. decolora eggs would hatch after 2 days.
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Copitarsia decolora (Guenée) on Asparagus from Peru
Therefore, eggs in garbage discarded the day of or the day prior to trash pickup would not hatch
before pickup, and would therefore pose little risk. For each importer we calculated the
probability that discarded asparagus would remain in the dumpster for more than two days,
p(remain two days), thereby allowing time for egg hatch and larval escape. Values of p(remain
two days) for a given number of weekly pickups were calculated by entering in a spreadsheet all
the possible distributions of pickups given the number of pickups per week. The industry
reported that little asparagus is discarded on Sundays and no facility reported pickups on all 7
days. We therefore assumed that asparagus was discarded and trash was collected MondaySaturday. The number of days across all possible disposal scenarios when asparagus would sit
more than two days prior to pickup was determined, and that sum was divided by the total
number of days from Monday-Saturday across all scenarios. Consequently, p(remain two days)
was 0.72 for 1 pickup per week, 0.49 for two pickups, 0.30 for three pickups, 0.16 for four
pickups, 0.08 for 5 pickups, and 0.0 for six pickups.
i. Number of eggs hatching in the dumpster
Eggs shipped from Peru (see Number of potentially viable eggs above) were placed in closed 60
ml plastic cups, with the attached asparagus stem. Some eggs were kept at 22 °C; while other
eggs were kept at 15 °C (see Day-degree accumulation by eggs during shipment). We tracked the
daily number of eggs hatching and calculated the percentage hatch. Across all packing sheds, 58
percent of the eggs shipped to the United States hatched upon arrival.
The probability of eggs hatching after shipment, p(hatching), was described by a Beta
distribution, which estimates the binomial probability of a success in the next trial given the
numbers of successes, s, and trials, n, already observed, as follows (e.g., Vose, 2000):
p(hatching) = Beta([s + 1],[ n − s + 1]) = Beta([316 + 1], [468 – 316 + 1])
[7]
where s = the number of eggs that hatched after shipment, and n = the total number of potentially
viable eggs.
j. Number of larvae escaping from the dumpster
A study was conducted in Peru to estimate the percentage of larvae that might crawl out of a
dumpster full of asparagus (Gould and Huamán 2006). Ten thousand C. decolora eggs on Kraft
paper were mixed with asparagus in ten garbage cans. Ninety percent of the eggs hatched, but
after one week only 1.2 percent of the larvae were caught in the sticky bands at the top of the
cans. Copitarsia decolora larvae typically crawl into the tips of the spears after hatching rather
than crawling away (J. Gould, personal observation). The number of larvae crawling out of the
dumpster was modeled using a Beta distribution (Eqn. (7)) with s = 108 escaped larvae and n =
8972 total larvae. The total number of larvae was less than the total number of eggs because not
all eggs were viable.
k. Number of potential mated females escaping from the dumpster
In this model we defined a “potential” mated female as a female larva crawling out of the
dumpster along with at least one male with which to mate. Males and unmated females cannot
found a population. There are currently no data on the availability of host plants, larval survival,
adult dispersal or host finding, so this model conservatively assumes that all larvae survive to the
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Copitarsia decolora (Guenée) on Asparagus from Peru
adult stage and all females are mated if a male is present. The probability that at least one female
and male escape from the dumpster depends directly upon the number of escaped larvae, NL.
Assuming an equal probability of being male or female (p♀ = p♂ = 0.5), then the number of
female larvae escaping, Nfem, is as follows:
Nfem = binomial(NL,0.5)
[8]
If at least one female and at least one male larvae escaped from a dumpster at one or more
facilites then the model returned a value of 1, indicating that a mated female was possible
nationwide. If no larvae escaped or if all females or all males escaped a 0 was returned,
indicating that no mated female was possible. Results were recorded separately for each importer
by season. The proportion of iterations with at least one potential mated female estimated the
probability of at least one potential mated female, p(any potential mated female). Knowing the
actual number of potential mated females is perhaps more important than knowing whether any
females were present or not because propagule pressure affects the probability of founding a
reproducing population (Beirne 1975, Kolar & Lodge 2001, Hopper & Roush 1993). Greater
initial population size can help overcome factors such as Allee effects (Allee et al. 1949) and
environmental fluctuations. Outputs included the total number of potential mated females at all
facilities, and also the maximum number of females at any individual facility. The maximum was
recorded because the risk is greatest at facilities with the most females.
l. Number of years to first potential mated female
Using the values for p(any potential mated female) by season, we calculated the number of years,
tMF, until a potential mated female first occurs as follows (e.g. Vose 2000):
tMFs = 1 + NegBin(s, ps) = 1 + NegBin(1, p(any potential mated female)s)
[13]
where NegBin indicates a negative binomial function, and s = 1 is the number of events of
interest. If the model predicted that p=0, we estimated the probability of a potential mated
female as 0.0001, or 1/10,000, which represents the lowest probability we were able to measure
given the number of iterations of the simulation.
3. Wholesaler model
The model for wholesale facilities was the same as the importer model with the following
exceptions.
a. Pounds of asparagus per wholesaler
The total amount of asparagus imported to the United States was calculated as for the importer
model (Eqn. (1)), but the amount received by the wholesale facilities had to be discounted by the
amount discarded by the importers. To specify the mean probability of importers discarding
asparagus, in a submodel we sampled from the reported values and calculated the mean
proportion discarded. This was repeated 10,000 times and the output distribution was the mean
proportion of asparagus discarded by importers, DI. The proportion discarded (DI) was sampled
from a histogram of mean values and frequencies, had a mean of 0.015, and 90 percent of the
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Copitarsia decolora (Guenée) on Asparagus from Peru
values were between 0.0087 and 0.022. Hence, the amount of asparagus moving from the
importers to the wholesalers, Aw, was as follows:
Aw = A – (A × DI)
[14]
where A is the total number of pounds of asparagus imported annually from Peru.
b. Number of wholesalers
The number of wholesalers that receive the asparagus leaving the importer facilities is a critical
parameter, but not one that was easily determined. The Perishable Agricultural Commodities Act
(PACA) database lists 7,768 wholesale facilities who are licensed to sell produce in the United
States, however many of these facilities handle only fruit or specialty vegetables. The number of
wholesalers receiving asparagus was estimated in a submodel using values for pounds received
per year as reported by wholesalers in the survey. We first used those reported values to estimate
the distribution for the average amount received per wholesaler. Then we divided the total
amount going to wholesalers from Peru with a value sampled from that distribution to determine
the number of wholesalers, W. This process was repeated 10,000 times. The output distribution
reflected our uncertainty in the number of wholesalers, and was a Pert distribution (Eqn. (1))
with Wml = 1,083 wholesalers, Wmin = 814, and Wmax = 1,429, rounded to the nearest integer. The
mean value was 1,096, and 90 percent of the values were between 911 and 1291. The amount of
asparagus from Peru per wholesaler was then the divisor of the sampled total amount and the
number of wholesalers, rounded to the nearest pound.
c. Amount of asparagus discarded
Wholesalers discarded from 1 to 7 percent of the asparagus handled at their facilities. For each
model iteration, the proportion discarded was sampled from a histogram of observed values and
frequencies. Pounds of asparagus discarded was then the product of the amount handled and the
proportion discarded.
d. Disposal method and frequency
Wholesale facilities put a smaller percentage of discards into a dumpster (32 percent) than
importers. Other disposal methods included trash compaction (32 percent), use in animal feed (4
percent), donation to a soup kitchen (18 percent) or food shelf (7 percent), and all other methods
(7 percent). No wholesaler reported composting or using a garbage disposal. On average the
garbage was picked up 3.8 times per week (range = 1 to 6).
We separately modeled facilities where 1) all produce was discarded in the dumpster, 2) a
mixture of methods was used, or 3) no asparagus was discarded in the dumpster. For an average
wholesaler in group (1), the probability of discards going into a dumpster, p(to dumpster), was 1,
while for those in group (3) it was 0. For group (2), p(to dumpster) was estimated as a Beta
distribution, with parameters based on reported values above: pmin = 0.01, pml = 0.32, and pmin =
0.99. This distribution was obviously relatively uncertain. The mean value was 0.38, and 90
percent of the values were between 0.11 and 0.70.
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Copitarsia decolora (Guenée) on Asparagus from Peru
e. Number of potential mated females
Model predictions related to Nfem were done as in the importer model above, except that
predictions were made separately for wholesale facilities having dumpsters emptied one to five
times per week, as well as facilities that used a mixture of disposal methods.
f. Years to first potential mated female at any wholesaler nationwide
To estimate the overall probability of at least one potential mated female occurring nationwide,
we first apportioned the number of wholesalers, W (above), into disposal-method groups, using
probabilities based on observed values in Beta distributions (Eqn. 3). The sum over all groups
was constrained to be no greater than W (not shown). Then, values for p(any potential mated
female) were found for each group (by season) as in Eqn. (9). Consequently, the number of
wholesalers with at least one potential mated female, Wfem, was as follows:
Wfem,g,s = binomial(Wg,s, p(any potential mated female)g,s)
[15]
where g is the disposal method group (e.g., 1 pickup per week, or mixture), and s is the season.
Not all wholesalers, however, are located where the climate is predicted to be suitable for longterm survival of C. decolora (see Climate Model below). We estimated the probability of a
wholesale facility being located in a climate suitable for C. decolora based on the results of
climate analysis using CLIMEX software. Despite an extensive search, we were unable to find
a comprehensive list of wholesalers that handle asparagus in the United States. We assumed that
the proportion of wholesalers located in a given area was the same as the proportion of the total
population that lived there. This assumption is reasonable if there are no large regional
differences in asparagus consumption. To determine the fraction of the population that lived in
an area suitable for establishment of C. decolora, we identified all zip codes that were classified
as favorable or very favorable in a CLIMEX model. We then tallied the population living within
those zip codes as measured during the 1999 census and expressed the results as a proportion of
the population in the contiguous United States. Under the assumption that wholesale facilities
that handle asparagus are distributed in direct proportion to the size of the population, 10.57 to
22.85% (depending on which CLIMEX model is consulted) of the asparagus leaving importer
facilities would end up in areas predicted to be suitable for C. decolora. The proportion of the
wholesale facilities in areas suitable for establishment was described as a Pert distribution, with
the minimum = 0.1057, the maximum = 0.2285, and the most likely = 0.1891. The number of
wholesalers in suitable climates with at least one potential mated female, Wsuit, was a binomial
process with n = Wfem, and p = p(suitable climate).
A separate tally was kept of the number of iterations in which any wholesaler—over all groups—
had at least one potential mated female. The proportion of iterations in which that happened
estimated the nationwide probability of a potential mated female occurring in a suitable spot,
p(nationwide mated female), by season. The number of years to the first potential mated female
at a wholesaler in a suitable area was then just Eqn. (13) with p(nationwide female).
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Copitarsia decolora (Guenée) on Asparagus from Peru
4. Retailer model
The model for retail facilities (supermarkets) was the same as the wholesale model with some
exceptions. Because the probability of getting a potential mated female was extremely low, we
ran 100,000 iterations to allow rare events.
a. Pounds of asparagus per retailer
First, we estimated the number of retailers, R, using the United States Food Stamp database. The
total number reported was 33,002, and we allowed for 10 percent variation on either side of that
(most likely) value in a pert distribution (i.e., Rmin = 33,002 × 0.9, and Rmax = 33,002 × 1.1).
The amount of asparagus discarded at a given facility was further reduced in this model, because
the asparagus was divided among all United States supermarkets and some asparagus is shipped
to restaurants. Between 30 and 98 percent of the asparagus leaving the wholesalers was
distributed to supermarkets for retail, and individual stores reported selling between 0 and 14,764
pounds of Peruvian asparagus per year. Given this level of uncertainty, we estimated the mean
amount of asparagus per retailer, AR,ml, as the total amount going to retailers from wholesalers,
AR,tot, divided by R. The other parameters in the Pert distribution for the amount of asparagus per
retailer, AR, were AR,min = 0, and AR,max = 14,764, from above. The resulting output had a mean
value of 4,724, with 90 percent of the values between 1,014 and 9,525.
b. Amount of asparagus discarded
The amount discarded was estimated as above, using the empirical histogram for grocery stores
with mean percentage discarded of 7.7 percent (range = 3 to 15 percent).
c. Disposal method and frequency
Supermarkets discarded even less asparagus in the dumpster (10 percent) than wholesalers. Most
was compacted (38 percent) or put in plastic bags (25 percent). Lesser amounts were composted
(14 percent) or put through a garbage disposal (13 percent). We assume that both dumpsters and
compost heaps are potential risks here. Garbage was collected on average 2.9 times per week
(range = 1 to 7). As above, facilities were separately estimated based on method of disposal.
C. Simulation of Reduced Egg Density
In Peru, managers are trying to develop IPM programs to reduce the density of C. decolora eggs
and data from two projects are available. Because C. decolora females prefer to oviposit on
asparagus fronds rather than on the stalks, a trap crop of asparagus fronds was allowed to
develop at two experimental farms. This method reduced the number of eggs per spear by 42
percent (Andres Casas, personal communication, October 2003). A second method uses high
pressure washing followed by washing with bleach and detergent to reduce the number of eggs
per spear by 69 percent. Combining the trap crop and washing procedures might reduce the
number of eggs per spear by about 83 percent. Other IPM tactics such as trapping, mating
disruption, and biological control could reduce egg density even further. We simulated
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Copitarsia decolora (Guenée) on Asparagus from Peru
reductions in the number of eggs per spear by factors of 10, 100, and 1000 by dividing the mean
number of eggs per spear by the appropriate reduction factor.
D. Climate Model
We used simulation analyses to evaluate the potential climatic suitability of different regions
within the contiguous US for establishment of C. decolora. Some model parameters were
estimated in laboratory studies. We used CLIMEX (ver 2.0) climate analysis software to
construct a process-oriented simulation model and forecast population dynamics of this insect.
Because the geographic distribution of C. decolora is incomplete and potentially inaccurate, the
method of iterative geographic fitting typically used to generate CLIMEX parameters was not
reliable. Instead, CLIMEX parameters were generated from empirical studies on the
temperature-dependent growth and development of C. decolora.
Models used United States monthly climate normals from 1971 to 2000 for 5,320 locations in the
continental United States. Relative humidity records were not available and were excluded. The
response variable in the model was Ecoclimatic Index (EI), an overall measure of climatic
suitability that ranges from 0 to 100 (Sutherst and Maywlad (1985) discuss in detail the
calculation of CLIMEX indices). EI = 0 indicates a climatically Unsuitable area for
establishment, 1 to 10 = Marginal, 11 to 25 = Suitable, and >25 = Very Suitable. Spatially
explicit results were exported into ArcView 3.2, and interpolation was performed by Inverse
Distance Weighting using Spatial Analyst 1.0. A 2.5 km2 grid was prepared; and the value at
each grid cell was estimated from the 12 nearest neighbors and a power factor of 2.
1. Temperature effects on population growth
CLIMEX uses a four parameter model to describe temperature requirements for population
growth. DV0 is the minimum temperature for population growth. DV1 is the lowest temperature
at which optimal growth is achieved. A constant optimal growth rate is maintained to DV2, the
upper temperature limit for optimal growth. Positive population growth continues but at a
linearly decreasing rate to DV3, the upper temperate limit for growth. At temperatures below
DV0 or above DV3, the size of a population remains constant or declines.
The impact of temperature on C. decolora population growth, as measured by the capacity for
increase (rc), was reported by Gould et al. (2005). In CLIMEX, these data were used to specify
the following parameters (Figure 7): DV0 = 7.3°C, DV1 = 24.0°C, DV2 = 26.3°C, and DV3 =
30.8°C. DV0 was the mean base temperature from bootstrap simulation (Gould et al., 2005),
while DV1 was the lower 95 percent limit of the confidence interval for optimal temperature, and
DV2 was the upper limit of that confidence interval. DV3 was the mean upper limit for
population growth [on asparagus]. Higher temperatures were not considered because C. decolora
eggs deposited at 29.5°C were not viable.
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Copitarsia decolora (Guenée) on Asparagus from Peru
Figure 7 Empirical data and parameter values in CLIMEX for temperature effects on population
growth rates of Copitarsia decolora, as measured on asparagus and artificial diet (Gould et al.,
2005).
2. Moisture effects on population growth
As with temperature, CLIMEX models the effects of moisture on population growth with a four
parameter model. Moisture indirectly affects the egg-, larval-, and adult-stages of C. decolora, as
mediated by the physiological condition of the host plant. Moisture can, however, directly impact
survivorship of late-instar larvae (pre-pupae) and pupae because they pupate in the soil.
3. Empirical studies
In the laboratory, C. decolora pre-pupae were placed in a soil-less growing medium with a
moisture holding capacity of 317.5 percent. The medium was oven dried and re-wetted to desired
moisture contents of 0, 75, 150, 225, and 300 percent gravimetric moisture. Three replicates
were destructively sampled after 4, 7 and 14 d to determine the percentage of surviving
individuals in each treatment. For all treatments, the effect of moisture significantly reduced
survivorship (F = 70.1, df = 4, 210, P < 0.001), but the effects of time (F=1.27, df=2, 210
P=0.28) and time-moisture interaction (F=0.13, df=8, 210, P=0.998) did not detectably affect
survivorship. Within the first 3 days, mortality was greatest at 300 percent moisture (P < 0.05),
and mortality at 200 percent moisture was greater than in any of the remaining treatments (P <
0.05). Morality at 75 percent moisture was lower than at any other treatment (P<0.05), but was
not different from 0 and 150 percent. Using these results, we adjusted the estimated capacity for
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Copitarsia decolora (Guenée) on Asparagus from Peru
increase of C. decolora at 23.5°C by fitting a 3-part, hinged linear model to the data using
maximum likelihood estimation (Solver feature in Excel) (Fig. 8). Parameter values were as
follows: SM0 = 0, SM1 = 0.001 (= 0.3 percent MHC), SM2 = 0.47 (= 149 percent MHC), and
SM3 = 2.6 (Table 4). The small value for SM1 reflected high survivorship of pre-pupae in very
dry soils.
0.14
Asparagus
Climex Description
Capacity for increase (rc)
0.12
0.10
0.08
0.06
0.04
0.02
0.00
0
50
100
150
200
250
300
Moisture Holding Capacity (%)
Figure 8. Empirical data and parameter values in CLIMEX for moisture effects on population
growth rates of Copitarsia decolora (Gould unpublished results).
4. Population responses to drought or flooding stresses
Because a large number of pre-pupae survived on dry and flooded substrates, we presumed that
neither flooding nor drought directly affected densities of C. decolora. Host-mediated indirect
effects of drought and flooding might be important to population dynamics but were not
considered.
5. Population responses to heat and cold stress
To estimate the effects of extreme temperatures we placed 100 neonates in 100 plastic cups into
environmental chambers set at constant temperatures of 1.7, 3.2, 5.5, 29.5, 31.3, 36.7, and 37.3ºC
with 14 h of daylight. Survivorship was recorded daily until all individuals had died. For each
temperature, we developed a generalized survivorship function by fitting a four-parameter
Gompertz model to the proportion of surviving individuals over time. We then solved each
equation for the number of days required for 95 percent of the population to die, and converted
that into weeks for CLIMEX.
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Copitarsia decolora (Guenée) on Asparagus from Peru
CLIMEX calculates cold stress based on estimated average temperature using the following
equation:
n
(TTCSA − T ) ⋅ THCSA ⋅ ∑ w ≈ 1
[16]
where TTCSA is the threshold for the accumulation of stress; T is temperature; THCSA is the rate
of stress accumulation, n is the integer number of weeks to ~100 percent mortality (non-integer
values are rounded up); and w is the number of weeks since the onset of stress. The population
goes extinct when the left side of the equation equals 1. We can rewrite Eqn. (16) as follows:
(TTCSA − T ) ⋅ THCSA ⋅
(TTCSA ⋅ THCSA) − (THCSA ⋅ T ) ≈
n(n + 1)
≈ 1.
2
2
n(n + 1)
[17]
So, regressing the transformed values of number of weeks until death (i.e., 2/(n(n+1))) against
temperature gives the threshold for the onset of stress accumulation and the rate of stress
accumulation (Fig. 9). Time to 100 percent mortality could not always be estimated reliably, so
we used time to 95 percent mortality as a reasonable approximation. At 1.7 and 3.2°C, 95 percent
mortality was achieved in 3 wk;, 4 wk at 5.5°C, and 41 wk at 9.7°C,. From the resulting linear
regression, we found THCSA = 0.022 and TTHSA = 0.2196/0.022 = 9.94 (Table 4).
High-temperature stress is similarly calculated, except that the function has a positive slope. A
significant complication arises because CLIMEX does not use average temperatures in the
calculation of heat stress. Rather, CLIMEX uses maximum air temperature, even though insects
may only experience this temperature for a few hours (often <4 h) per day. In constanttemperature experiments, we found that 95 percent mortality at 29.5°C was predicted to occur in
7 wk; in 3 wk at 31.3°C, in 2 wk at 34.5°C, and in 1 wk at both 36.7 and 37.3°C. However,
insects in typical diurnal cycles would probably survive longer if only exposed to high
temperatures for short periods each day. Thus, CLIMEX probably overestimates the mortality
insects would likely experience under typical diurnal temperature cycles. As a result, time to 95
percent mortality was adjusted using the following assumptions: (a) insects are exposed to high
temperatures for only 4 h per day and would die at the rate (1/[time to 95 percent mortality])
measured in our constant temperature experiments; (b) for the remainder of the day, insects
would die at the rate measured for 29.5°C; and (c) exposure during one time period had no
impact on the mortality rate during another time period. Our adjusted time to 95 percent
mortality at 29.5°C was 7 wk, 6 wk at 31.3°C, 5 wk at 34.5°C, and 2 wk at 36.7 and 37.3°C.
From the regression equation (Fig. 10), we found that THHS, the rate of heat stress accumulation
was 0.0405 and that the threshold temperature for the accumulation of heat stress, TTHS, , was
29.8°C (Table 4). The regression was significant but very uncertain, however, so the parameter
estimates were uncertain as well. The 95 percent confidence limits for estimation of the slope
(i.e., THHS) were 0.0007 to 0.08 and were -2.56 to 0.14 for the intercept. Calculation of TTHS
using the limits of the slope and the intercept gave highly variable and biologically meaningless
Rev. Original
June 30, 2006
22
Copitarsia decolora (Guenée) on Asparagus from Peru
results that ranged from -206 to 3644°C. Thus, we are highly uncertain about the threshold and
rate for stress accumulation due to heat.
Table 4. Parameter values for heat stress in the baseline and test (T#) CLIMEX models (see
text). Blank cells indicate the value was unchanged from the baseline model.
Section
Parameter
Heat stress
TTHS (ºC)
THHS (ºC)
Model version
M1
M2
M3
31
32
0.004 0.004 0.004
Baseline
29.8
0.0405
M4
32
0.0405
Transformed weeks to 95% mortality
0.3
Mortality estimated from experiments
Predicted
95% CI
0.2
0.1
Y = 0.2196 - 0.02219T; R2=0.97; P=0.02
0.0
-0.1
0
2
4
6
8
10
12
Temperature (°C)
Figure 9: Relationship between cold temperatures and mortality of C. decolora, which gives the
cold-stress parameters Tcs and rcsin CLIMEX (see text). Lines show the linear regression and 95
percent confidence interval (CI) of the estimate.
Rev. Original
June 30, 2006
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Copitarsia decolora (Guenée) on Asparagus from Peru
Transformed weeks to 95% mortality
0.5
Mortality estimated from experiments
Predicted
95% CI
0.4
0.3
0.2
0.1
0.0
-0.1
Y = -1.2084 + 0.0405T; R2=0.78; P=0.048
-0.2
-0.3
28
30
32
34
36
38
Temperature (°C)
Figure 10: Relationship between high temperature and mortality of C. decolora in the
laboratory, which gives the heat-stress parameters TTHS and THHS in CLIMEX (see text).
III. RESULTS AND DISCUSSION
A. Probabilistic modeling
1. Importers
The probability that at least one potential mated female could escape from the asparagus pathway
at a minimum of one importer facility approached 100 percent and mean tMP (time to first
potential mated female) was 1 year for all three time periods (Table 5). The number of potential
mated females escaping from dumpsters differed for the three time periods, however. Across all
importers, the model estimated that the mean number of potential mated females escaping within
two weeks during September to December was 64, but that dropped to 25 for the transition
periods, and to 7 for February to May (Figure 11, Table 5). Even during the February-May
season, however, the model predicted that one might find up to 70 potential mated females at a
single importer facility (Figure 12) and potential mated females could be expected at up to 5 of
the importer facilities (Table 5). Clearly the risk was greater during the September to December
time frame, when 80 percent of the asparagus from Peru is imported, but the risk remained high
during the other periods.
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Copitarsia decolora (Guenée) on Asparagus from Peru
Table 5. Risk of potential mated females escaping the asparagus pathway at importer,
wholesaler, and retailer facilities. Values are averages, with 5th and 95th percentiles given in
parentheses.
Facility
Importer
Wholesale
Retail
Rev. Original
Variable
Probability of 1+ potential
mated female escaping
nationally
Years to first potential
mated female nationally
Importers with potential
mated females (no.)
Potential mated females at
all facilities (no.)
Max potential mated
females at a single facility
(no.)
Probability of 1+ potential
mated female escaping
nationally
Years to first potential
mated female nationally
Potential mated females at
all facilities (no.)
Max potential mated
females at a single facility
(no.)
Probability of 1+ potential
mated female escaping
nationally
Years to first potential
mated female nationally
Potential mated females at
all facilities (no.)
Max potential mated
females at a single facility
(no.)
Sep-Dec
Season
Jan, Jun-Aug
Feb-May
0.9992
0.9933
0.8643
1 (1, 1)
1 (1, 1)
1 (1, 2)
5 (2,7)
4 (1, 6)
2 (0, 4)
64 (13, 145)
25 (4, 59)
7 (0, 21)
37 (6, 96)
15 (2, 41)
5 (0, 14)
0.26018
0.0492
0.0122
4 (1, 10)
20 (2, 60)
82 (5, 244)
0.3 (0, 1)
0.5 (0, 0)
0.01 (0, 0)
0.05 (0, 0)
0.01 (0, 0)
0.001 (0, 0)
<0.00001
<0.00001
<0.00001
>114 (6, 343)
>114 (6, 343)
>114 (6, 343)
0.007 (0, 0)
0.009 (0, 0)
<0.00001 (0, 0)
<0.00001 (0, 0)
0.008 (0, 0)
<0.00001 (0, 0)
June 30, 2006
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Copitarsia decolora (Guenée) on Asparagus from Peru
700
600
September-December
500
400
300
200
100
1600
0
1400
January, June-August
Frequency
1200
1000
800
600
400
200
0
6000
February-May
5000
4000
3000
2000
1000
0
0
50
100
150
200
250
300
Number of Potentail Mated Females at All Importers
Figure 11. Predicted numbers of potential mated females summed across all importer facilities
during three time periods for 10,000 iterations of the @Risk model
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June 30, 2006
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Copitarsia decolora (Guenée) on Asparagus from Peru
1200
September-December
1000
800
600
400
200
3000
0
January, June-August
Frequency
2500
2000
1500
1000
500
8000
0
February-May
6000
4000
2000
0
0
50
100
150
200
250
300
Maximum number of potential mated females at a single importer facility
Figure 12. Predicted maximum number of potential mated females at a single importer facility
during three time periods for 10,000 iterations of the @Risk model
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June 30, 2006
27
Copitarsia decolora (Guenée) on Asparagus from Peru
2. Wholesalers
Once the asparagus leaves the importer facilities it gets divided up and sent to wholesale
warehouses. The @Risk sub-model calculated that there were on average 1082 warehouses
handling asparagus (95 percent CI = 814 to 1429). Each warehouse was estimated to handle
124,021 pounds (95 percent CI = 99,698 to 152,801) of Peruvian asparagus per year. Although
the percentage of asparagus discarded was higher, the number of pounds that got discarded in
one place at one time was considerably less at wholesale facilities. In addition, wholesalers
discarded a lower percentage of their waste in dumpsters (32 percent). Therefore, the estimated
risk of getting a potential mated female was lower at wholesale facilities. The probabilities of
one or more potential mated females escaping from the produce pathway were 0.26, 0.05, and
0.01 for the Sep-Dec, Jan/Jun-Aug, and Feb-May time periods respectively (Table 5). The model
estimated that a potential mated female could escape in 4 years during Sep-Dec, but the
maximum number of potential mated females at a single facility averaged less than one and did
not exceed three. During Jan/Jun-Aug and Feb-May the number of years to first potential mated
female were 20 and 82; again with an average of less than one potential mated female escaping
the produce pathway when females did escape.
3. Retailers
The model did not predict that any mated females would be produced at individual retail
facilities. Because the model ran for 100,000 iterations, the probability of one or more potential
mated females escaping from the asparagus pathway was less than 0.00001 (Table 5). The model
predicted that the first potential mated female would be produced on average after more than 114
years for all seasons.
Some supermarkets may be in close proximity to one another in large cities, but due to a lack of
data on mate finding ability and proximity of grocery stores we could not model the risk of
obtaining a male and female at more than one facility in close proximity. Given that the
maximum number of potential mated females produced per facility in a month was less than
0.00001 for all three time periods, it seems reasonable to assume that the few individuals that
might be produced, if they even survived to the adult stage, would be unlikely to find one
another (see Calabrese and Fagan 2004 for a discussion of mate finding when insects reach
adulthood asynchronously).
4. Simulating reductions in egg densities
Logically, reducing the number of eggs per spear would decrease the risk of establishment by C.
decolora, and egg density is something that can be measured as asparagus is imported to the
United States. We simulated reductions in the number of eggs per spear by factors of 10, 100,
and 1000. Even with a ten-fold reduction in egg density, mean tMP was <5 yr at importer facilities
for all three time periods (Table 6). Reducing the egg load by 100-fold gave mean tMP > 5, even
during September to December, the time period with the greatest risk. A 1000-fold reduction
increased mean tMP to 294 yr or greater. In terms of numbers of potential mated females,
however, reducing the egg density substantially reduced the maximum number of potential
mated females one would expect to see at a single importer facility. The average maximum
Rev. Original
June 30, 2006
28
Copitarsia decolora (Guenée) on Asparagus from Peru
number of potential mated females declined from 37 to 4 per facility during Sep-Dec (Table 7)
with a 10-fold decrease in egg density. The average maximum number of potential mated
females was predicted to be less than 2 during the transitional and Feb-May seasons. For
warehouse facilities, reducing the egg density by 10-fold or greater increased the number of
years to the first expected potential mated female to over 57 years for all seasons (Table 8).
Table 6. Predicted years to first potential mated female at importer facilities when the number of
eggs per spear is reduced up to 1000-fold. Values are averages by season, with 5th and 95th
percentiles given in parentheses.
Egg Density
Multiplication Factor
1
0.1
0.01
0.001
Years to first potential mated female
Sept-Dec
Jan, Jun-Aug
Feb-May
1 (1, 1)
1 (1, 1)
1 (1, 2)
1 (1, 2)
2 (1, 4)
5 (1, 15)
7 (1, 21)
30 (2, 91)
249 (13, 748)
344 (18, 1032)
3333 (171, 9980)
9999 (513, 29947)
Table 7. Predicted maximum number of potential mated females found at a single importer
facility as the number of eggs per spear is reduced up to 1000-fold. Values are averages by
season, with 5th and 95th percentiles given in parentheses.
Egg Density Multiplication
Factor
1
0.1
0.01
0.001
Maximum number of mated females at a single
facility
Sept-Dec
Jan, Jun-Aug
Feb-May
37 (6, 96)
15 (2, 41)
5 (0, 14)
4 (0, 11)
1 (0, 5)
0.3 (0, 2)
0.2 (0, 1)
0.04 (0, 0)
0.004 (0, 0)
0.003 (0, 0)
0.0003 (0, 0)
<0.0001 (0, 0)
Table 8. Predicted years to first potential mated female at wholesale facilities when the number
of eggs per spear is reduced up to 1000-fold. Values are averages by season, with 5th and 95th
percentiles given in parentheses.
Egg Density
Multiplication Factor
1
0.1
0.01
0.001
Rev. Original
Years to first potential mated female
Sept-Dec
Jan, Jun-Aug
Feb-May
2 (1, 3)
5 (1, 14)
19 (1, 56)
57 (3, 169)
131 (7, 392)
>144 (8, 431)
>136 (7, 408)
>134 (7, 402)
>144 (8, 431)
>136 (7, 408)
>134 (7, 402)
>144 (8, 431)
June 30, 2006
29
Copitarsia decolora (Guenée) on Asparagus from Peru
B. CLIMEX modeling
In the baseline model the coast of California south of San Francisco Bay was classified as either
Suitable or Very Suitable (Fig. 10). All of Florida was predicted to be Unsuitable due to the
effects of heat stress.
As mentioned previously, we were highly uncertain about the heat stress parameter values, so we
tested alterations to those parameters within the estimated confidence limits. In particular, we
considered the implications if C. decolora were more heat tolerant. Heat tolerance can be
reflected by a lower rate of stress accumulation, a higher threshold for the onset of stress, or
both. Our exploration of the effect of different CLIMEX parameters is intended to reduce (but
not minimize) the chances of a Type II error, i.e., characterizing a Suitable area as Unsuitable.
We recognize that this increases the chances of a Type I error, i.e., characterizing Unsuitable
sites as Suitable.
In test model 1 (M1), with only THHS reduced, several small coastal areas along the Gulf of
Mexico and Atlantic Ocean became Marginal (Fig. 11), and some very small pockets in LA, FL,
GA, and SC became Suitable. The increase in Suitable area in the Southeast was expected after
characterizing C. decolora as slightly more heat tolerant, but, significantly, large areas of the
Southeast remained Unsuitable.
In M2, with TTHS increased, much more area of the Southeast was classified as Marginal or
Suitable (Fig. 12). In particular, the area around Miami became Suitable. This change was much
more significant than the change in THHS.
In M3, we decreased THHS and increased TTHS. After this change, large areas of the Southeast
became Marginal or Suitable, and very few areas within Florida, including Miami, remained
Unsuitable (Fig. 13).
Lastly, in M4, we further increased TTHS from M3. Now, significant portions of the Gulf States
were Suitable or Very Suitable for establishment of C. decolora, and the area around Miami was
Very Suitable (Fig. 14).
Rev. Original
June 30, 2006
30
Copitarsia decolora (Guenée) on Asparagus from Peru
Suitability
0 (Unsuitable)
1-10 (Marginal)
11-25 (Suitable)
25-63 (Very Suitable)
No Data
Figure 10. Relative suitability (Ecoclimatic Index) of the continental United States for C.
decolora from the baseline model in CLIMEX.
Suitability
0 (Unsuitable)
1-10 (Marginal)
11-25 (Suitable)
25-43 (Very Suitable)
No Data
Figure 11. Relative suitability (Ecoclimatic Index) of the continental United States for C.
decolora from model M1, in which THHS had a ten-fold lower value of than in the baseline
model (see text for more details).
Rev. Original
June 30, 2006
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Copitarsia decolora (Guenée) on Asparagus from Peru
Suitability
0 (Unsuitable)
1-10 (Marginal)
11-25 (Suitable)
25-63 (Very Suitable)
No Data
Figure 12. Relative suitability (Ecoclimatic Index) of the continental United States from model
version M2, in which TTHS was 2.2°C greater than in the baseline model.
Suitability
0 (Unsuitable)
1-10 (Marginal)
11-25 (Suitable)
25-64 (Very Suitable)
No Data
Figure 13. Relative suitability (Ecoclimatic Index) of the continental U.S. from model version
M3, in which TTHS was increased by 1.2°C, and THHS was decreased ten-fold compared to the
baseline model.
Rev. Original
June 30, 2006
32
Copitarsia decolora (Guenée) on Asparagus from Peru
Suitability
0 (Unsuitable)
1-10 (Marginal)
11-25 (Suitable)
25-63 (Very Suitable)
No Data
Figure 14. Relative suitability (Ecoclimatic Index) of the continental U.S. from model version
M4, in which TTHS was 2.2°C greater, and rhs was decreased ten-fold, compared to the baseline
model.
IV. CONCLUSIONS
A. Current risk
The probabilistic model indicated that the risk of at least one female and male C. decolora larva
escaping into the wild was greatest at importer facilities and during the September to December
time frame. While escape at importer facilities is most likely to occur on imports during the
period from September to December, the differences between that and the other time periods did
not seem to justify seasonal differences in handling and disposal of asparagus. Asparagus from
Peru enters the U.S. through two ports: Miami and Los Angeles. The climate modeling software
CLIMEX strongly indicated that the Los Angeles area was climatically Very Suitable for
establishment (Figures 10-14). Miami may be climatically Suitable for establishment, but we are
uncertain about that classification. Regardless, from both pathway and climate modeling, we
conclude that the risk of establishment by C. decolora is greatest for asparagus discarded by
importers in the Los Angeles area. Establishment is less likely but possible on discards by
importers in the Miami area. Escape of potential C. decolora mated females is less likely from
asparagus discarded by wholesalers anywhere, especially during the transitional and Feb-May
time periods, and even less likely at retailer’s facilities. Ongoing efforts to reduce the number of
C. decolora eggs per asparagus spear in Peru are promising but current probabilistic modeling
indicates large reductions (up to 100-fold) would be required to significantly reduce the number
of years before one might expect a potential mated female to escape at an importer facility. If one
Rev. Original
June 30, 2006
33
Copitarsia decolora (Guenée) on Asparagus from Peru
considers the predicted average maximum of four potential mated females per importer facility
to be unlikely to establish a reproducing population, then perhaps only a 10-fold reduction in egg
density would be sufficient to reduce the risk of an establishment.
The current model does not account for some important factors that would reduce the likelihood
of establishment such as finding host plants, completing development, and finding a mate.
Consequently, the model currently overestimates the risk of establishment by C. decolora. That
is unfortunate, but data do not exist to account for these other processes. In this case, a more
conservative estimate of risk was reasonable. However, evidence from biological control
introductions shows that populations are unlikely to persist when few individuals are released.
Experimental releases of leaf beetles demonstrated that the probability of establishment increases
with an increase in the number of adults released (Grevstad 1999). When twenty gravid
females—which had already become adults and mated—were placed directly on their host
plants, only one population persisted for a significant length of time. In addition, the colonization
percentage of biological control agents released at the appropriate stage directly onto host plants
was only about 10 percent when fewer than 5,000 individuals were released, but 78 percent when
31,000+ individuals were released (Beirne 1975). We point out these studies to highlight the
conservative nature of our model.
B. Risk mitigation possibilities
The probabilistic model we developed identified the greatest risk of establishment of C. decolora
at the importer facilities. This is based primarily on the large volume of asparagus imported, the
large percentage that is discarded in dumpsters, and their location in areas where the climate
would be suitable for establishment. This information can be used by regulators and industry to
develop ways to mitigate the risk of establishment of C. decolora with methods other than
fumigation with methyl-bromide. We provide some examples here:
1) Move the importer facilities away from coastal CA and the southeastern United States.
2) Reduce egg density 10-100 fold through IPM practices.
3) Use a trash compacter or garbage disposal for all discarded asparagus at importer facilities.
This would require monitoring for compliance
An aspect of risk mitigation with methods other than methyl bromide fumigation that was not
addressed by this risk assessment model is the possibility that less asparagus would be discarded
because the shelf life of the asparagus would be enhanced. Asparagus is kept below 4ºC during
shipment because it quickly begins to deteriorate at warmer temperatures, and asparagus must be
warmed during fumigation. The reduced shelf life of asparagus as a result of fumigation has
undoubtedly led to a higher level of discards and a higher risk level than one might expect with
other mitigation measures.
Rev. Original
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Copitarsia decolora (Guenée) on Asparagus from Peru
V. References
Allee, W.C., A.E. Emerson, O. Park, T. Park, and K.P. Schmidt. 1949. Principles of animal
ecology. Saunders, Philadelphia.
Beirne, B.P. 1975. Biological control attempts by introductions against pest insects in the field in
Canada. The Canadian Entomologist 107: 225-236.
Calabrese, J.M., and W.F. Fagan. 2004. Lost in time, lonely, and single: Reproductive
asynchrony and the Allee effect. The American Naturalist. 164(1) 25-37.
Caton, B.P. 2005. How to predict mating pair formation and numbers of mating pairs formed as
binomial processes in pest risk assessment models. Center for Plant Health Science and
Technology, USDA-APHIS-PPQ, Raleigh, NC. April 2005. 10 pp.
EPA. 1993. Safer Disposal For Solid Waste: The Federal Regulations for Landfills. No.
EPA/530 SW-91 092, Washington, DC: Environmental Protection Agency (EPA). 18 pp.
Gould, J.R., and M. Huamán. 2006. Copitarsia decolora (Lepidoptera: Noctuidae) larvae
escaping from discarded asparagus: data in support of a pathway risk analysis. Accepted by
Journal of Economic Entomology.
Gould, J.R., R. Venette, J. Davidson, and P. Kingsley. 2000. A Pest Risk Assessment for
Copitarsia Species: A Case Study in Support of a Risk Based Resource Allocation Model.
88 pp.
Gould, J.R., R. Venette, and D. Winograd. 2005. Effect of Temperature on Development and
Population Parameters of Copitarsia decolora (Lepidoptera: Noctuidae). Environmental
Entomology. 34 (3): 548-556.
Grevstad, F.S. 1999. Experimental invasions using biological control introductions: the influence
of release size on the chance of population establishment. Biological Invasions 1: 313-323.
Hopper, K.R., and R. T. Roush. 1993. Mate finding dispersal, number released, and the success
of biological control introductions. Ecological Entomology 18: 321-331.
Kolar, C.S., and D.M. Lodge. 2001. Progress in invasion biology: Predicting invaders. Trends in
Ecology and Evolution 16:199-205.
Orr, R.L., S.D. Cohen & R.L. Griffin, 1993. Generic nonindigenous pest risk assessment process
(for estimating pest risk associated with the introduction of nonindigenous organisms). U.S.
Department of Agriculture, Animal and Plant Health Inspection Service (Internal report),
Riverdale, MD.
Simmons, R.B., and M.G. Pogue. 2004. Redescription of two often confused noctuid pests,
Copitarsia decolora (Guenée) and C. incommoda (Walker) (Lepidoptera: Noctuidae).
Annals Ent. Soc. Am. Annals of the Entomological Society of America. 97:1159-1164.
Simmons, R.B., and S.J. Scheffer. 2004. Evidence of cryptic species within the pest Copitarsia
decolora (Guenée) (Lepidoptera: Noctuidae). Annals Ent. Soc. Am. 97: 675-680.
Sutherst, R.W. and G.F. Maywald. 1985. A computerised system for matching climates in
ecology. Agriculture, Ecosystems and Environment. 13: 281-299.
USDA-APHIS-PPQ. 2005. Pest interception network (PIN309) [On-line]. Plant Protection and
Quarantine, Animal and Plant Health Inspection Service, U.S. Department of Agriculture,
Riverdale, MD.
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U.S.TRADE IMPORTS - HS 10-DIGIT CODES.
http://www.fas.usda.gov/ustrade/USTImHS10.asp?QI=
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Copitarsia decolora (Guenée) on Asparagus from Peru
Venette, R.C., and J.R. Gould. 2006. A pest risk assessment for Copitarsia spp., cutworms of
economic importance south of the U.S. border. Euphytica. 19: 1-19.
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Copitarsia decolora (Guenée) on Asparagus from Peru
Appendix A. Letter sent to randomly selected wholesale facilities.
Corporate Resource, Inc.
5021 Vernon Ave. # 155 Minneapolis, MN 55436
…implementing internal solutions…
952-926 4602 ♦ Fax 952-926 3933
[email protected]
Dear Selected Produce Wholesalers:
Question: Can I ask you to complete the enclosed five-question survey (it should take approximately 10
minutes)?
Why: Because currently asparagus from Peru must be fumigated with Methyl Bromide, this fumigation is
costly and reduces the quality of the asparagus. Depending on how much asparagus is thrown away,
and how it is discarded, this requirement may be changed.
Background: The United States Department of Agriculture (USDA), Animal Plant Health Inspection Service
(APHIS) contacted me regarding a risk assessment of moths on asparagus from Peru. As you know,
APHIS’s is responsible for protecting and promoting U.S. agricultural health. APHIS is concerned about
the risk posed by these moths, however, port officials spend a considerable amount of time inspecting
asparagus and overseeing fumigation. APHIS wants to make sure that efforts spent on inspection
activities are correlated with risk.
These moths are not present in the United States and are currently "actionable quarantine pests."
Because the majority of asparagus from Peru was found to be infested with this moth’s eggs, USDAAPHIS now requires all asparagus from Peru to undergo mandatory fumigation. An assessment
conducted by USDA-APHIS in 2000 determined that the risk from this moth is probably high, but that the
confidence in the assessment was quite low because of gaps in available data.
APHIS has asked me to help quantify the amount of asparagus that follows the various channels from
importer to wholesaler to retailer to customer. They need to know how much asparagus continues
through each channel to the customer and how much is thrown out at each step. And, if the asparagus is
thrown out, where does it go? Is it put through a trash compactor or placed in a dumpster, etc.?
Because moth eggs can also arrive on broccoli, which is less perishable than asparagus, we are including
broccoli in the survey. Fresh imported fruit also is heavily treated to prevent the establishment of fruit flies in
the United States. APHIS has asked that we survey for the fate of two fruits, one more perishable than the
other, to assist in assessing the risk of establishment of fruit flies.
Restaurants and Supermarkets: Similar surveys will be sent shortly to supermarkets and restaurants. The
survey has been completed by the majority of asparagus importers and can be seen on the web by going
to http://www.cphst.org/programs.cfm, and than scroll down the left until you get to:
2003_ESA_Poster_-_Fate_of_Produce. This poster will provide you more information about the overall
project.
Confidentiality: The information you provide will only be used for this analysis and kept confidential. No
reports will be made that identify a specific company or market area in the U.S.
Thank you for your time and consideration of this request. Dr. Juli R. Gould at USDA, or myself, would
appreciate the opportunity to discuss any questions, or concerns, you may have on this project.
Sincerely,
Jon Seltzer
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Copitarsia decolora (Guenée) on Asparagus from Peru
Appendix B. Survey sent to randomly selected wholesale facilities.
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Copitarsia decolora (Guenée) on Asparagus from Peru
Appendix B: continued
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Copitarsia decolora (Guenée) on Asparagus from Peru
Appendix C. Survey sent to supermarket facilities.
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Copitarsia decolora (Guenée) on Asparagus from Peru
Appendix C: continued.
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