Changing Strategies for Plant Bug Management in Tennessee

1
Changing Strategies for Plant Bug Management in
Tennessee
Scott Stewart, Cotton IPM Specialist
2
Problem and Question

• Both TPB and CPB have become an increasing
  problem
• Boll weevil eradication, Bt cotton
• Most obvious impact during midseason
• Applies to stink bugs
• Are insecticides and rates recommended for TPB
  equally effective for CPB?

3
Solution

• Contrast insecticide efficacy across replicated
  trials that had both species present
• Cumulative average counts in check plots vs. each
  selected insecticide
• Standard rates of
• acephate (Orthene, 0.33-0.5 lb)
• dicrotophos (Bidrin, 6-8 oz)
• oxamyl (Vydate, 10-12 oz)
• synthetic pyrethroids (mid-labeled rates, as a
  group)
• imidacloprid (Trimax, 1.5 oz)
• thiamethoxam (Centric, 1.5-2.0 oz)
• novaluron (Diamond, 9 oz.)
• Mid-season tests during 2004-2005
• First rating date only (4-6 DAT)

Stewart, Lentz, Hanks, Willis, Steckel
4
Insect Control TPB vs. CPB
Rating unit was 2 or 3 drop cloth samples per
treatment per trial (N number of trials in
comparison) Karate Z (6), Mustang Max (3), or
Baythroid (1)
5

• Tarnished Plant Bug
• Summary of Midsouth Field Trials (2003 - 2004)
• Insecticide Rate
  N Control (all states)
• Centric 0.05 12
  55.5
• Trimax 0.047 11
  43.2
• Vydate 0.33 7
  58.0
• Orthene 0.50 6
  67.6
• Bidrin 0.40 6
  66.2
• Diamond 0.058 4
  53.5
• Percent control tended to be slightly higher in
  Tennessee than in other
• states (resistance?)

6
TPB and CPB Trial
Total plant bugs (late July early August),
Lauderdale Co., 2005
7
Effect of Nozzle Type on TPB Control
Jeff Gore (USDA ARS) - Field treatments with
insects caged on plants and rated 48 hours after
application. All tests were done at 9.4 GPA, 40
PSI and 5 MPH.
8
Residual Control of TPB
Stewart et al. - Field to lab assay with adults
caged on leaves for 24 hours. Leaves were
collected 1 hour, 2 days and 5 days after
treatment. Application was 8.0 GPA, 50 PSI using
TX6 nozzles (July 20, 2005).
9
The Point

• Essentially no insecticides provide effective
  residual control of plant bugs beyond 5-7 days
• Toxicity is the most important component of
  efficacy (residual is secondary)
• Our best midseason products typically have the
  lowest residual (e.g., Bidrin, acephate, Vydate)
• You can make a good product mediocre (and promote
  resistance)
• Over use (particularly of the same chemistry)
• Using the right insecticide at the wrong time
• Poor application or using bottom-end rates

10
Controlling Midseason Plant Bugs

• Clouded plant bug, in general, is easier to
  control than the tarnished plant bug
• On average, CPB populations were higher than TPB
  populations
• Bidrin, acephate and Vydate provided the most
  consistent control of both species
• This meshes well with controlling stink bug
• In Tennessee, pyrethroids still have good fit,
  especially when bollworms are present, but
  tank-mixing may be necessary in some situations
• Midseason - plan on making two applications on
  4-5 day schedule, especially for TPB and when
  populations are well above threshold

11
Is Resistance a Real Threat?

• Already know it can happen, even in Tennessee
  (e.g., pyrethroids)
• Data from surrounding states is concerning
• Gordon Snodgrass (USDA ARS, Mississippi)
• Field and laboratory (vial) assays with TPB
• Documented resistance to pyrethroids and Bidrin

12
Vial Assay Locations with 3-Fold or Higher
Resistance to Orthene

• LC50 Dose
  Mortality Permethrin
• 
  Orthene dis. dose (15ug) 3 h
• Avon, MS 14.37
  52
• Greenville, MS 12.03
  48
• Rolling Fork, MS 11.10
  24
• Lake Providence, LA 10.74
  28
• Transylvania, LA 9.96
  68
• Clarksdale, MS 9.43
  48
• Winona, MS 9.83 36
• Bruce, MS 9.91
  38
• Elliott, MS 9.56
  36
• Gore Springs, MS 9.18 46
• Mean
  10.61 42

Susceptible check colony had LC50 3.1
(Snodgrass)
13
Do Lab Assays Translate to the Field?

• Orthene Resistance Ratio 3.6 Rolling Fork
• Orthene Resistance Ratio 1.6 Indianola
• Mean Percent Mortality 48 h
• Rolling Fork Indianola
• Check 5 7
• Orthene (0.5) 32 62
• Orthene (1.0) 63 90
• Centric (0.05) 55 73

Snodgrass and Gore (Field study, 2005)
14
New Plant Bug Recommendations
15
Full Season Plan

• New Plant Bug Recommendations
• A guideline (not a law)
• Goal - logical sequence of insecticide rotation
  for IRM
• Reducing use of OP, carbamate and pyrethroid
  insecticides in June
• Reserving use for mid-season (higher rates more
  affordable)
• Higher likelihood of need (critical window)
• Using Carbine, Centric, Intruder and Trimax in
  June window where they work and fit best
• Somewhat less disruptive (also control aphids)
• Banding to reduce cost
• Not a perfect plan
• e.g., Vydate regimes for nematodes

16
Observations

• Best approach economically, and for insecticide
  resistance management, is to treat as needed
• Scheduled applications are often wasted and
  increase selection for resistance
• Especially true during pre-bloom window
• Piggy-backing insecticide with herbicide and pix
  applications does make sense (sometimes)
• Reduces application costs
• Effectively lowering treatment thresholds
• But flexibility is key
• Plant bug applications should still be triggered
  by pest pressure and square retention
• Flex cotton may help insecticide timing

17
Final Thoughts

• Cotton Insect Control Guide
• www.utcrops.com