Research
Cactoblastis cactorum (Lepidoptera: Pyralidae) in the United
States: An Immigrant Biological Control Agent or an Introduction
of the Nursery Industry?
Robert
w:
Pemberton
ABSTRACT Miami APHIS-Plant Protection & Quarantine
records showed 13 Cactoblastis cactont11t Bergroth interceptions in commercial nursery imports of Opulltia from the Dominican Republic between 1981 and 1986. These interceptions and the large volume of underinspected cacti that have been imported from the Dominican Republic and other countries with C. cactont11t suggest that the moth may
have entered Florida as an unintended commercial introduction.
The present problem with C. cactontm relates the difficulty of preventing
pest introductions
with commercial plant imports and, to a lesser degree, the historical introduction
of the moth to the Caribbean and
habitat destruction that has contributed to the rarity of some American Opulltia.
T
HERE
IS NO EVIDENCE THAT AGENTS INTRODUCED
FOR THE BIOLOG-
ical control of weeds have reduced populations
of native
nontarget plants, although there are a few reports of t::1eiruse
of native plants as hosts (Center 1982, Andres 1985, Turner 1985,
Turner et al. 1987). The recent advent of Caetobias tis cactorum Bergroth in Florida, however, appears to alter this perception (Simberloff 1992). Although not deliberately introduced to Florida, the
moth was purposely introduced to the Caribbean for the control of
weedy Oplllttia cacti (Habeck and Bennett 1990). It has been assumed that the moth spread naturally to Florida from the Caribbean
(Habeck and Bennett 1990, SimberloH 1992). It may be an immigrant, reaching the U.S. mainland on its own, but it is also possible
that it was brought in accidently through commerce.
Caetoblastis eaetorum was found established in the Florida Keys
in October 1989 (Habeck and Bennett 1990). This moth, a native of
Argentina, Uruguay, and Paraguay, was used successfully to control
seven species of pest Opulltia cacti in Australia, Hawaii, and elsewhere (Dodd 1940, Fullaway 1954, Julien 1992). Within its native
range, C. eactorum is known to breed in 1 species of CleistDcactlls
and all but one Opulltia (at least 15 species); the species not used is
the usual host of Cactoblastis doddi Heinrich (Mann 1969). Because
C. caetomm attacks most all Opulltia species, its recent introduction into the United States is a cause for concern. Indeed, i: is currently threatening
three rare or restricted Florida cacti: Opulltia
spillosissima (Martyn), O. triaeantha (Willdenow), and O. cubensis
Britton and Rose, whose populations have been reduced by habitat
destruction
(Bennett and Habeck, in press). Comparisons
of the
mean low temperatures of some of the known South American localities of the moth with various North American localities suggest that
C. caetortlm has the potential to spread throughout the warmer areas of the United States and Mexico. In the United States, it should
be able to reach Charleston, SC; San Antonino, TX; and the lower
altitude areas of New Mexico, Arizona, and California nortt to Sacramento.
The degree of the moth's use of, and impact on, Opulltia species
varies in its native area and the places where it has been employed as
a biological control agent (Mann 1969, McFadyen 1985, Moran
1984; Pemberton, unpublished data). Although specific interactions
cannot be predicted, the moth appears to have the ability to reduce
significantly
the populations
of some rare and common North
American Opuntia species. Two of the species, O. illermis Candolle
and O. strieta (Haworth), successfully controlled in Australia, are
native to North America (Dodd 1940). One of these, O. stricta, C.
eactorum's most common host in Florida, grows around the Gulf of
Mexico (Long and Lakela 1971) and could assist the moth's spread
to Texas and Mexico. There are noCleistoeaetus species in the Unit-
230
ed States but there are 46 species of native Opuntia (USDA 1982),
one of which (Opl/Iltia treleasei [Coulter]) is a federally protected
endangered species (U.S. Dep. Interior 1993a); 12 other taxa (6 subspecies and 6 species) are under review for protected status (U.S.
Department of the Interior 1993b).
Following successful introductions
elsewhere in the world, C.
cactorum was introduced to Nevis Island in 1957 where it dramatically controlled the target cacti, O. dillel1ii (Ker-Gawler), O.lindheimeri Englemann, and O. triacal1tha (Willdenow) (Simmonds and
Bennett 1966). Because of its success, it subsequently
was introduced to other islands with cactus problems: to nearby Montserrat
and Antigua in 1962 and to Grand Cayman, below Cuba, in 1970
(Bennett et a!. 1985). It also established on these islands and, additionally, was found in Puerto Rico in 1963, presumably moving on
its own from the Lesser Antilles (Garcia-Tuduri
et al. 1971). Subsequently, the moth was found in Haiti, the Dominican Republic, and
the Bahamas (William Starmer, personal communication).
In 1989,
it was detected in the Florida Keys by Carol Lippencott, of the Fairchild Tropical Garden, Miami (Simberloff 1992). She searched for
the moth because it was predicted to spread to Florida (Starmer et al.
1987), based on its occurrence in the Bahamas, Cuba, and elsewhere
in the West Indies (SimberloH 1992).
After learning that cacti are imported to Florida from other countries by the state's nursery industry, I contacted the USDA-APHIS,
Plant Protection & Quarantine (PPQ), Hyattsville, MD, to learn of
possible interceptions of C. cactorum at U.S. ports of entry, and the
status of cactus introductions
before 1989 when the moth was first
detected in Florida. Three PPQ data sources were used: (1) the
Hyattsville computer base of pest insect interceptions; (2) individual
interception records (PPQ 309 forms) on file at the Plant Inspection
Station in Miami, FL; and (3) the Miami station's monthly reports of
importation of regulated articles (PPQ 280 forms), in which summary statistics of cactus imports are noted.
The computer database covering the years 1985-1992 contained
4 records of C. eaetorum interceptions.
Three interceptions
occurred in Miami and involved commercial imports of O'Jtmtia pads
from the Dominican Republic. The other interception was of 01J1mtia fruit detected in personal airline baggage brought to Dallas from
Cancun in Mexico. C. caetorum is not known to be established in
Mexico, although this interception from Cancun suggests that it
may now occur there.
Table 1 shows the 17 interceptions of C. cactorum made at the
Miami station, including the 3 Hyattsville computer records for
Miami. All of the Opwltia in which the moth was detected were
commercial imports of vegetative material intended for propagation. All of the detected C. eactorum were alive, half of the intercepAMERICAN
ENTOMOI.()(;IST
•
Winter 1995
Table 1. Interceptions
of C. cacto",m at the USDA-APHIS-PPQ
inspection station in Miami, FL
Date
found
Aug.lnl
Sept. 19112
Aprilln3
June 1983July 1983
Mar. 19115
April 19116
.June In6"
Oct.
Oct.
Nov.
Nov.
Nov.
Sept.
Sept.
Sept.
Sept.
1986
19116
19116
19116
19116
1991'
1993
1993
1993
Origin
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Dominican
Haiti
Haiti
Haiti
No.
found
Republic
Republic
Republic
Republic
Republic
Republic
Republic
Republic
Republic
Republic
Republic
Republic
Republic
Republic
39
5
2
8
2
I3
1
1
1
1
1
1
10
1
10
2
1
adults
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
larvae
Shipment
sIze
3,850
1,200
1,000
1,000
1,490
80
5
4
5
2,400
1
1
1,650
8
4
10
7
cuttings
cuttings
cuttings
plants
cuttings
plants
crates
crates
era res
cuttings
crate
crate
plants
boxes
boxes
boxes
boxes
plant
%
inspected
20
5
10
2
10
1.3
20
25
20
10
100
100
10
12.5
25
10
14.2
Host cacti in which C. cactomm were found were reported only as
species, except in the tbree cases indicated by footnotes.
-Of/III/tia
Maverick.
{'Of/lllltia
Espina.
'Of/III/tia
ita/ica Tenore.
O/JIII/ita
tions had more than one individual, and, other than the adults found
in 1981, all of the interceptions were of larvae. The interceptions of
C. cactomt11, except 3 from Haiti entering with cacti sent by ship,
were in cacti arriving by air. All shipments in which the moths were
detected were fumigated with methyl bromide. The insects intercepted in 1981 and 1982 were identified only as members of the Phycitinae the subfamilv to which Cactoblastis and most other cactus
mo~hs belong. Gi~en the large number of C. cactomm subsequently
intercepted from the Dominican Republic, it seems probable that
these too were C. cactorllt11.
Because 7 of the 17 C. cactorzml interceptions
were made in
] 986, the monthly summaries of cactus imports for that year were
examined. Unfortunately, these summaries lump all cacti genera and
species together, and the inspection work sheets from which the information was compiled no longer exist. Those imports from countries known to have C. cactomm are listed in Table 2. Although the
quantity of Opllntia imported from countries in 1986 cannot be
known precisely, some of the inspectors (such as Gordon Muraoka)
who worked in the APHIS-PPQ Miami station during that time
remember the nature of cactus imports for that period. Imports from
Brazil were grafted cacti that were not Oplmtia. Most of the shipments from the Dominican Republic and Haiti contained species of
Opt/lltia and other cacti genera. Most of the Oplmtia imports consisted of single pads packed in layers of newspaper in banana-type
boxes (2 by 2 by 4 ft). Dominican Republic shipments were fumigated during 6 of the 12 mo in 1986.
It is, and was in the 1980s, APHIS-PPQ policy to inspect from
1-25% of each commercial horticultural
import shipment (internal
operational
guidelines for inspection). Usually ",2% of each shipment is examined (G. Muraoka,
personal communication).
After
reading a shipment manifest, the inspector requests that a certain
number of boxes, representing samples of different plant species or
varieties and sizes, be removed from the shipping container or taken
off the pallet. The samples are selected by the customs broker, the
owner, or his designee. Air shipments are more accessible (boxes sitting on a pallet) and are much smaller, usually <30 boxes. Shipments
in marine truck trailer shipping containers often contain hundreds
of boxes. Sampling representative types of air and sea shipments results in a higher percentage of air shipments being inspected. The
AMFRICAN ENTml010GIST
•
Winter 1995
long spines of many of the Opuntia species also inhibit their inspection because specimens are difficult to handle and repack after inspection.
Cactoblastis cactorllm has been detected at some of Florida's
commercial nurseries since 1991 (Florida Department of Agriculture and Consummer Services, Division of Plant Industry, Entomology Section detection records). Costa Nurseries in Dade County,
Florida, have had C. cactorum problems for several years (Tony
Costa, Costa Nursery, personal communication).
These nurseries
are the largest importers of cacti entering the United States through
Miami. Most of the cacti that they import are grown at their nursery
in the Dominican Republic. That nursery also has had problems
with C. cactorum; the moth infests up to 10% of the cactus plants
despite control efforts.
The 13 C. cactorum interceptions in Miami prior to 1989 (Table
1) were all in air freight from the Dominican Republic. Most of the
larger volume shipments were, however, marine (Gordon Muraoka,
personal communication).
This suggests that the moth may have
evaded detection in the less thoroughly inspected marine shipments.
It also may have gone undetected in air freight because only a small
percentage of this material was inspected and the larvae, which feed
internally in the pads, are less obvious than many external feeders.
Given the large numbers of cacti entering the United States from the
Dominican Republic, >350,000 specimens in 108 shipments in
1986 alone, this is not unlikely. The moth could have been introduced from anywhere in its current range, but the chance of its entering undetected increases with the large commercial shipments.
Because the moth was detected first in the Keys based on a prediction of its natural spread to Florida, the assumption has been that it
became established there and then spread rapidly northward (Bennett and Habeck 1996). The information that I have assembled suggests that C. cactorum could have been introduced by the nursery
industry, become established somewhere in the southern counties of
Florida, and then spread rapidly northward and southward.
The
likely
introduction
of C.
cactorum
into
the United
States
through commercial plant introductions
points to the difficulty in
the detection and exclusion of pests associated with plant imports.
During 1993,,,,456 million exotic plants were imported through the
16 USDA-APHIS-PPQ
plant introduction
facilities (Center et al.
1995).
Regardless of whether C. cactorum is an immigrant or an introduction, problems associated with the moth would probably not
exist if the moth had not been introduced into the Caribbean. This
introduction was, in my opinion, unwise because the Caribbean and
other warm areas in the Western Hemisphere are rich in OfJulttia
species that could have (and have) become nontarget hosts for the
moth. Australia, South Africa, Mauritius, and Hawaii, where the
moth was previously used, have no native cacti that could have become hosts.
Another problem is that the cactus species (0. triacantha) for
which the moth was introduced into Nevis is native to Nevis and
other parts of the West Indies and Florida. It is now considered a
Table 2. Imports
Miami in 1986
Country
of origin
with C. cactorum, entering
of cacti, from countries
No.
shipments
No.
imported
No.
fumigated
719,139
356,394
11,991
200
13,985
217
Brazil
Dominican Republic
Haiti
Jamaica
St. Barthelemy
29
108
4
2
1
7
1
Argentina
Total
1
145
24
1,087,556
24 killed
231
valued rare plant in Florida (U.S. Department of the Interior 1993b).
The moth's introduction
into Nevis and its usc in the Caribbean was
during a different era, before the increased development,
spread,
and legal codification of native plant conservation values. Relatively few biological control introductions
have been made against native plants that arc weeds (Julien 1992). The practice has been
advocated by some (Deloach 1980, Johnson 1985) and questioned
by others (Andres 1980, Pemberton 1985a, Turner 1985). The issue
is complex but relates primarily to differing perspectives and attitudes about the worth and uniqueness of native plants that are
weeds and the appropriateness
of using biological control to reduce
them. Introduced weeds with close native relatives are routinely targeted, but more attention is given to the safety of nontarget plants in
this era than in earlier times, when the safety concerns were focused
on economic plants (Pemberton 1985b, Soper 1992).
Acknowledgments
I thank the following individuals for sharing data and information essential to this story: Susan Broda-Hydorn and Gordon Muraoka (Miami), Joe
Cavey (Hyattsville, MD), and Richard Elliot (Dallas), all ofUSDA-APHIS-PPQ; Debra Chalot and Harlo von Wald (Miami), and Michael Thomas
(Gainesville), all of the Florida Department of Agriculture and CO::Jsummer
Services, Division of Plant Industry; Tony Costa of (Costa Nurseries, Homestead, FL); William Starmer (Department of Biology, Syracuse University);
Maria Solis (USDA-ARS Systematic Entomology Laboratory, Beltsville,
MD); and Dale Habeck (Department of Entomology and Nematology, University of Florida, Gainesville). Ted Center (Aquatic Plant Management
Laboratory, USDA-ARS, Ft. Lauderdale, FL); William Kemp (Rangeland
Insect Laboratory, USDA-ARS, Bozeman, MT); and William Starmer and
Peter Stilling (Department of Biology, University of South Florida, Tampa)
kindly reviewed the manuscript.
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Received for publicatioll 27 December 1994; accepted 3 August 1995.
•
Robert Pemberton is a research entomologist with USDAARS Aquatic Plant Management Laboratory, 3205 College Avenue, Ft. Lauderdale, FL 33314. He does research on biological
control of insect and weeds. and on arthropod-plant mutual isms
(involving extrafloral nectaries and leaf domatia), which result in
plant protection. He recently contributed to the American Entomologist on ethnoentomology, an interest stimulated by many
years of work in Asia.
AMERICAN
ENTOMOLOGIST
•
Willter 1995