Use and Cost of Insecticides to Control Potato
Psyllids and Zebra Chip on Potatoes
Author(s): Joseph Guenthner, John Goolsby and Gina Greenway
Source: Southwestern Entomologist, 37(3):263-270. 2012.
Published By: Society of Southwestern Entomologists
DOI: http://dx.doi.org/10.3958/059.037.0302
URL: http://www.bioone.org/doi/full/10.3958/059.037.0302
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VOL. 37, NO. 3
SOUTHWESTERN ENTOMOLOGIST
SEP. 2012
Use and Cost of Insecticides to Control Potato Psyllids and Zebra Chip on
Potatoes
Joseph Guenthner1, John Goolsby2, and Gina Greenway1
Abstract. Zebra chip disease has become a serious problem in North America.
Data from growers in Kansas, Nebraska, and Texas enabled us to document
insecticide use and costs to control zebra chip in 53 commercial fields of potato,
Solanum tuberosum L. The number of different insecticides used in Texas
decreased from 16 in 2009 to 10 in 2011. The most commonly used insecticides in
all three states were Admire (imidacloprid) and Movento (spirotetramat). Growers in
Texas spent an average of $740 per hectare annually during 2009-2011, while
those in Kansas and Nebraska spent $700 per hectare. Costs varied among fields
in the same locations. Issues raised by this study included: insecticide use
progression, control of other insects, yield loss, quality loss, strategies to manage
zebra chip, and the impact of zebra chip on the competitive positions of potatogrowing areas.
Introduction
Zebra chip disease in potatoes, Solanum tuberosum L., was first noted in
Mexico in the 1990s (Munyaneza et al. 2009) and the Lower Rio Grande Valley of
Texas in 2000 (Goolsby et al. 2007a,b). Zebra chip spread to potato-production
areas of the southwestern US including Texas, Kansas, Nebraska, New Mexico,
California, and Colorado (Crosslin and Bester 2009). More recently, zebra chip was
found in the Pacific Northwest (Rondon and Hamm 2011) and New Zealand
(Crosslin et al. 2010).
The causal agent of the disease was shown to be graft-transmissible
(Crosslin and Munyaneza 2009) and was later identified as Candidatus Liberibacter
solanacearum (Lin et al. 2009), which is related to other alpha-protobacteria, most
notably citrus greening (Huanaglongbing) ‘Candidatus Liberibacter asiaticus’
(Gottwald 2010). In potatoes, zebra chip lowers yield potential, discolors fries/chips,
causes storage losses, and limits exports. Great economic losses have occurred in
the areas impacted (Rosson et al. 2006), which have led to intensive pest
management programs to minimize the impact of the disease (Goolsby et al.
2007b).
The potato psyllid, Bactericera cockerelli (Sulc), harbors Ca. L.
solanacearum in its gut microflora and vectors the disease to potatoes and other
plants (Munyaneza et al. 2010) through its feeding activity (Buchman et al. 2011).
The potato psyllid and its solanaceous host plants are indigenous to the
southwestern US and northern Mexico. The potato psyllid is known to exploit the
1
Department of AERS, University of Idaho, Moscow, ID 83844-2334.
USDA-ARS, 2413 E Hwy 83, Weslaco, TX 78596.
2
263
‘climatic trumpet’ of the Great Plains to migrate long distances and exploit
solanceaous host plants that include the native wolfberry, Lycium spp. and
nightshades, Solanum spp. (Rowe 1993, Goolsby 2007b).
Molecular markers have been used to separate two distinct populations of
potato psyllid from California and the Great Plains (Liu et al. 2006), and from the
Lower Rio Grande Valley (Jackson et al. 2009). These differences reflect stable
breeding populations in each region, although there is evidence of gene flow
between them. Each population may have a unique life history and exposure to
wild and cultivated solanaceous hosts, which influences acquisition and
transmission of Ca. Liberibacter solanacearum by potato psyllids.
Laboratory studies have shown that cooler or warmer temperatures can slow
or inhibit the development of Ca. Liberibacter solanacearum in infected tubers
(Munyaneza et al. 2011). Therefore, under field conditions, abiotic factors of
weather such as temperature, humidity, and rainfall may also influence the
acquisition, transmission, and seasonal association of Ca. Liberibacter
solanacearum by potato psyllids.
Research in Colorado, Kansas, Nebraska, and Texas shows seasonal
phenology of the potato psyllid and its associated Ca. Liberibacter solanacearum
pathogen in commercial fields and nontreated checks. Data gathered from this
research may ultimately be used to adjust the insecticide inputs based on the
seasonal disease pressure for each potato-growing region. As a step toward
profitable control of zebra chip, insecticide use and costs for potato growers in these
potato-growing regions were analyzed. Specific objectives were to:
(1) determine grower use of insecticides to control zebra chip
(2) estimate costs of insecticide materials and applications
Methods
Potato psyllids and zebra chip disease were surveyed in commercial potato
fields at nine locations in Kansas, Nebraska, and Texas for the 2009, 2010, and
2011 crops. Each week, cooperating growers self-reported the insecticides they
used to control psyllids and zebra chip. While the insecticides may have also been
used to control other pests and some may not have been labeled for potato psyllids,
the growers reported what they thought might help control zebra chip. The following
data were collected to estimate cost to control zebra chip:
(1) insecticides growers applied
(2) number of insecticide applications
(3) application rates
(4) insecticide prices
(5) insecticide application costs
For items (1) and (2) the weekly data reported by the commercial potato
growers who participated in the study were used. The data included specific
insecticide applications for 53 fields in Kansas, Nebraska, and Texas. Because the
grower-reported data did not include application rates, insecticide labels were
searched for information on recommended rates. Maximum rates were chosen
based on discussions with cooperating growers and scientists involved in the
project. The maximum rate was not selected if use for the entire season was near
the limit. Insecticide prices and pesticide application costs were obtained from
university sources (Patterson and Painter 2010, 2011) and interviews with
agricultural chemical dealers.
264
Results
Cooperating growers in Texas used 18 insecticides for the 2009-2011 crops
(Table 1). The number of materials decreased from 16 in 2009 to 10 in 2011. The
two most widely used insecticides in 2011 were Movento (spirotetramat) and
Admire (imidacloprid). Movento was used in 100% of the fields in 2011, increased
from 70% in 2009 and 92% in 2010. Admire use followed a similar upward trend.
One chemical that decreased in use was Agri-Mek (abamectin), but use of the
generic form of the product, Epi-Mek, increased.
Table 1. Insecticide Use to Control Zebra Chip and Psyllids, Texas, 2009-2011
Insecticide
Fields treated (%)
Common/trade name
Active ingredient
2009
2010
2011
Admire Pro
Imidacloprid
40
75
92
Agri-Mek
Abamectin
40
67
25
Asana
Esfenvalerate
30
17
Baythroid
B-Cyfluthrin
10
8
Belay
Clothianidin
8
Beleaf
Flonicamid
20
17
25
Epi-Mek
Abamectin
30
33
58
Fulfill
Pymetrozine
70
42
50
Leverage 360
Imidacloprid + beta-cyhalothrin
10
8
Movento
Spirotetramat
70
92
100
Oberon 2 SC
Spiromesifen
40
58
42
Platinum
Thiamethoxam
30
8
Radiant SC
Spinetoram
10
Thimet
Phorate
10
8
Thiodan
Endosulfan
10
8
8
Venom (foliar)
Dinotefuran
30
8
17
Venom(soil)
Dinotefuran
10
8
Vydate C
Oxamyl
8
Number of fields in sample
10
12
12
Total number of insecticides used
16
16
10
Average number of insecticides used per field *
5.3
5.0
5.3
Average number of insecticide applications *
8.7
7.9
7.9
*Differences are not statistically significant
Cooperating growers in Kansas and Nebraska used 21 insecticides for the
2009-2011 crops (Table 2). Most of the chemicals used in these two states were
the same as those used in Texas. Movento was the most frequently used
insecticide during all 3 years. Trends were less distinct for Kansas and Nebraska
because of variation in the number of fields from three in 2009 to 12 in 2010 and
four in 2011, but the number of insecticides used decreased from 20 in 2010 to 11
in 2011.
265
Table 2. Insecticide Use to Control Zebra Chip and Psyllids, Kansas and Nebraska,
2009-2011
Insecticide
Fields treated (%)
Common/trade name
Active ingredient
2009 2010 2011
Abacus
Abamectin
8
Admire Pro
Imidacloprid
100
58
50
Agri-Mek
Abamectin
42
25
Asana
Esfenvalerate
100
25
25
Baythroid
B-Cyfluthrin
33
75
Beleaf
Flonicamid
25
Dimate
Dimethoate
25
Endigo
Lambda-cyhalothrin + Thiamethoxam
25
Endosulfan
Endosulfan
8
Epi-Mek
Abamectin
25
Fulfill
Pymetrozine
33
25
Leverage 360
Imidacloprid
8
25
Movento
Spirotetramat
100
75
75
Oberon 2 SC
Spiromesifen
33
25
Platinum
Thiamethoxam
42
Pounce
Permethrin
25
25
Regent
Fipronil
17
Scorpion
Dinotefuran
33
Thimet
Phorate
100
25
Thiodan
Endosulfan
17
25
Vydate C
Oxamyl
8
Number of fields in sample
3
12
4
Total number of insecticides used
5
20
10
Average number of insecticides used per field
4.3
6.3*
4.0
Average number of insecticide applications
7.7
9.5
6.0
*Statistically significant
In Texas, growers applied insecticide an average of 7.9 times in 2010 and
2011, down from 8.7 applications in 2009 (Table 1). In Kansas and Nebraska, the
maximum was 9.5 applications in 2010, dropping to 6.0 in 2011 (Table 2). The
average number of insecticides used per field was stable in Texas, ranging from 5.0
in 2010, to 5.3 in 2009 and 2011. The number of insecticides used in Kansas and
Nebraska varied over a wider range, from 4.0 to 6.3.
Insecticide material and application costs exceeded $320 per hectare in all
but one of the 53 fields during the 3-year period (Table 3). The most expensive was
$1,272 per hectare at Imperial, NE, in 2010 and Olton, TX, in 2011. The average
cost at all Texas locations during all 3 years was $740 per hectare. The average for
Kansas and Nebraska was less at $700, but the costs in 2010 and 2011 were near
the Texas averages for those years.
The 2009-2011 trend for average insecticide costs was flat for Texas and
increasing for Kansas and Nebraska (Fig. 1). For some locations, costs varied over
a wide range in the same year. For example, 2010 costs in six fields at McAllen,
TX, ranged from $435 to 1,232 per hectare. Costs for the three fields at Pearsall,
TX, in 2011 varied from $381 to 991 per hectare.
266
Table 3. Insecticide Costs per Hectare for Zebra Chip and Psyllid Control in
Kansas, Nebraska, and Texas, 2009-2011
Year/location
2009
Kansas, Garden City
Texas, Dalhart
Texas, McAllen
Texas, Olton
Texas, Pearsall
2010
Kansas, Garden City
Nebraska, Alliance
Nebraska, Imperial
Nebraska, Minden
Texas, Dalhart
Texas, McAllen
Texas, Olton
Texas, Pearsall
2011
Kansas, Garden City
Nebraska, Alliance
Nebraska, Minden
Texas, Dalhart
Texas, McAllen
Texas, Olton
Texas, Pearsall
Low ($/h)
High ($/h)
Average ($/h)
3
2
4
1
3
529
707
732
551
529
596
722
850
551
1,117
551
714
787
551
883
3
3
3
3
2
6
1
3
749
731
790
323
798
435
668
373
985
874
1,272
473
958
1,232
668
558
907
778
981
377
878
895
668
446
1
2
1
3
4
2
3
1,095
361
78
622
566
593
381
1,095
570
78
884
835
1,272
991
1,095
464
NA
750
676
934
689
No. of fields
Discussion
This study documented the use and costs of insecticides applied by growers
in three states to control zebra chip in 2009-2011. It provides a starting point for
future research and raises several issues related to control of this disease.
Potato growers dealt with a new pest about which little was known. Only
three insecticides were labeled for potato psyllids when the crop was planted in
2009. In addition to the three labeled products, growers applied insecticides labeled
for other potato pests, hoping they might also suppress psyllids. Meanwhile,
pesticide firms obtained during the 2009-2011 period, labels for 12 insecticides
against potato psyllids. As time passed, growers narrowed the total number of
different insecticides they applied. Several growers said that, through trial and
error, they learned what insecticides were most effective for controlling potato
psyllids without causing problems for beneficial species.
Growers reported the insecticides they used to control zebra chip. They did
not report what they would have applied if zebra chip and potato psyllids were not
problems. Before zebra chip, growers in the McAllen, TX area grew potatoes
without use of insecticide. In other areas, some of the insecticides applied before
zebra chip may overlap with the list of insecticides growers used to control zebra
chip. In those cases, we may have overestimated insecticide costs for zebra chip.
267
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Fig. 1. Average insecticide cost per hectare for zebra chip and psyllid control, 20092011.
The economic impact of zebra chip is greater than the costs of using
insecticides. Grower revenue is also affected by zebra chip. In spite of multiple
applications of insecticides, yield losses and quality losses continue to be problems.
The quality losses include rejections of potatoes by processors. Estimates of yield
losses vary over a wide range. A survey of experts who attended a zebra chip
meeting in November 2011 found estimates of yield loss varying over a wide range,
from 0.5 to 75%. The average was 18%.
Zebra chip researchers involved in a project funded by USDA SCRI have a
primary goal of developing a comprehensive, environmentally responsible program
to manage zebra chip disease.
Economic analysis of alternative disease
management strategies will be part of that effort. The best strategies could provide
growers with tools to reduce insecticide costs as well as reduce yield and quality
losses.
Zebra chip costs could affect where potatoes are grown in North America.
Some potato plantings could shift from areas where zebra chip is a serious problem
to areas where the problem does not exist. The list of areas where zebra chip is not
a problem is shrinking. In 2011, zebra chip and potato psyllids were found in Idaho,
Oregon, and Washington. If Eastern Idaho growers would have zebra chipinsecticide costs similar to growers in this study, potato production costs would
increase 17%, from $4,320 to 5,060 per hectare (Patterson 2011), which could
affect the competitive position of the largest potato-producing state.
268
Acknowledgment
We thank the USDA SCRI, Texas A&M University, and the University of
Idaho for supporting this research.
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