1. Manuel Campos and Don Henne
Insecticide efficacy trials on potato psyllid, Bactericera cockerelli, in the Lower Rio Grande Valley of Texas
Manuel Campos and Don Henne
Subtropical Pest Management Laboratory Texas A&M AgriLife Research  Weslaco, TX
Introduction
The potato psyllid, Bactericera cockerelli is the vector of Zebra chip disease (ZC), ‘Candidatus Liberibacter solanacearum’, which causes plant mortality and diminishes tremendously the quality of tubers. Acceptable and marketable tubers depend the effort of researchers, and the evaluation of insecticides as part of the management to reduce this psyllid and ZC incidence. Here, we summarize insecticide evaluation trials conducted in the Lower Rio Grande Valley of Southern Texas during winter
Trial 5.
Treatment
Oz / acre
Torac * 21
Movento * 5
Fulfill *
5.5
Untreated
* + Dyne-amic 0.25% v/v
2 applications, 1 week apart
Trial 6.
Treatment
Oz / acre
Torac * 21
Movento * 5
Fulfill *
5.5
Untreated
* + Dyne-amic 0.25% v/v
1 application
Conclusions
Psyllid populations were not uniform throughout fields resulting in high variation among treatments. On the other hand, there is more control of psyllid populations under greenhouse conditions, and looking forward the challenge to scale similar results to the field. Also, there is a need of continue the test of products that can prevent feeding and/or test insecticides that can have a ‘knock-down’ effect on psyllids, thus, reducing ZC incidence in tubers.
Trial 7.
Treatment
Oz / acre
Sivanto * 14
Admire Pro *
8.7
Platinum *
2.67
Venom *
1.5
Untreated
* 1 foliar application 'Knockdown'
Methods and Materials
Field trials. Potato plots (cv ‘Atlantic’) were established at the Texas A&M AgriLife Experiment Station in Weslaco, TX. Potatoes were planted in 2 row plots (30´ length x 6.6´ width) during January 2013 and fertilized with N32 (150 lb/acre) at 3-week post-emergence and at bloom. Insecticide rates were applied according to manufacturer’s protocols. A tractor equipped with CO2 tanks delivered the insecticide to 2 rows by 6 nozzles at 50 PSI and at rate of 40 gal of water/acre. At each evaluation date, 20 leaves were collected from 10 random plants from each plot. Eggs and nymphs were counted by a stereomicro-scope. At harvest, 20 tubers were collected from each plot to asses ZC defects by fried chip test. RCB design was used to arrange treatments with 4 replicates/treatment.
Statistical Analysis. Psyllid eggs and nymphs data were overdispersed and a square-root transformation was performed. Data were pooled over time prior to runing a t-test. Percent ZC data were analyzed by using Proc freq and Proc Genmod. Significant differences were estimated at P=0.05. All analysis was done in SAS software.
Trial 8.
Treatment
Dose Unit
Unit/acre
Application # 1
Untreated 2
Requiem + Movento *
1 + 5
pint + oz
Sivanto 14 oz
Movento * 5 3
2,3 4
1,2
Requiem
pint
Movento (local)
1,2,3 6
10.5 7
1.04
quart 8 z 9
Oberon
1,2,3,4,5 10
quart + oz
* + Dyne-Amic 0.25% v/v.
Greenhouse trials. Either potatoes (trials 5 and 6) or tomatoes (trials 7 and 8) were planted in 1 gal pots under greenhouse conditions. Plants were an average height of 12 and selected to be treated and infested (caged) with psyllids. At the time of application, plants were transported to the chemical room and insecticides were applied at recommended rates with a CO2 backpack sprayer 20 PSI. Five males and five females captured from insectary cages into plastic pipette tips and 20 nymphs at 4th and 5th stage collected also from insectary were then released into the treated and caged leaves. Three leaves per plant were caged with a fine mesh bag (6 length  4 width). Finally, plants were returned to the greenhouse and grown under conditions of 70-80°F and 60-80% relative humidity.
Trial 1.
Treatment
Rate
oz/acre 1
Aza Direct 20 2
Aza Direct + M-pede 2% 16 3
Scorpion
5.5 4
Magister 24 5 32 6
Onager 7 8
Nexter
10.67 9
Untreated
Total # applications = 5
Trial 2.
Application
Treatment lb/acre
Interval Days 1
Grandevo 14 2
Movento oz/ac 3
Untreated
Results
Trial 1. Only Aza Direct 16 oz + M-Pede showed lowest eggs laid and was significantly different to untreated (highest). However, nymph counts did not differ from each other. On the other hand, only Magister 32 oz and Nexter scored less than 15% of ZC defects.
Trial 2. Grandevo alone showed lowest egg counts, followed by Grandevo + Movento, but they differed from untreated. Similar trend was shown on nymph counts. Grandevo + Movento and untreated were not significantly different from each other. In addition, the lowest ZC defect was by Grandevo alone with 5% defected tubers.
Trial 3. Overall, all treatments showed no difference with untreated on egg or nymph counts. However, only Transform 2.25 oz, Radiant 4 oz and untreated showed more than 13% ZC defects.
Trial 4. Treatments were not significantly different from untreated, either on eggs or nymphs counts. However, treatments 1,2,3 and 4 scored less than 14% of ZC defects.
Trial 5. All treatments scored lower egg counts than untreated after 14 days after treatment, and nymph counts scored less than untreated after the first week. Tubers from the Torac treatment did not show any ZC symptom.
Trial 6. Torac suppressed egg and nymph populations and ZC symptoms. This product was followed by Movento and subsequently by Fullfil. All treatments were significantly different from untreated.
Trial 7. All treatments suppressed egg laying and were significantly different to untreated. On the other hand, all treatments suppressed nymph populations, except Sivanto (ca. 50 %). However, Sivanto suppressed almost 60% of adults.
Trial 8. All treatments suppressed egg, nymph and adult populations after the second week and last until the week 5.
Trial 3.
Treatment
Oz/Acre 1
Untreated 2
Transform
1.5 3 4
2.25 5
Movento
5.0 6
Radiant 7 8
Blackhawk
2.78 9
3.5
Dyne-amic 0.25% v/v to all treatments
Trial 4.
Application starting at
TRT / Program
Rate / acre
days after emergency 1
Verimark
0.176 lb
At planting
* Foliar program 14 2 28 3
Verimark + Vydate
0.176 lb oz 4 5
Vydate
68 oz 6
Admire + Vydate
8.7 oz oz 7
Admire Pro
8.7 oz 8 9
Untreated control
Oz / acre
Movento + Agrimek
Movento
5.0
Agrimek
8.0
Fulfill
5.5
Radiant
Applications were made weekly
MSO was applied to all foliar program insecticides at 0.25% v/v;
Acknowledgments: Thanks to the Pest Management Laboratory members. This research was supported by grants from SCRI award # and the Texas Department of Agriculture. Additional funding was provided by Bayer CropScience, Dow Agroscience, Marrone Bio Innovations, Nichino America, Gowan. Thanks to J.W. Farms for providing seed material for planting.