IPM for Stink Bugs in Cotton: What do we know and What do we need to know

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IPM for Stink Bugs in Cotton What do we know
and What do we need to know?

• P. Roberts, M. Toews, and J. Ruberson, University
  of Georgia
• Jeremy Greene, Clemson University
• J. Bacheler and J. Van Duyn, North Carolina State
  University
• E. Blinka and A. Herbert, Virginia Tech

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Identifying Practical Knowledge and Solutions
for Managing The Sucking-Bug Complex In Cotton
Research In The Southeast Region
Southeast State Support Committees
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Insecticide Applications per AcreGeorgia Cotton,
1986-2007
Boll Weevil Era
Two significant events have changed cotton IPM
during the last 20 years.
-Active BWEP- (does not include BWEP sprays)
----------Boll Weevil Free-----------------------
--------------Bt Cotton--------------
Heliothines
Boll Feeding Bugs
Source Beltwide Cotton Conferences
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Losses Due to Stink BugsSoutheast and US
(1992-2005)
Beltwide Cotton Conferences
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Bug Pest Status ElevatedNo Coincidental Control

• Stink Bugs
• Southern green
• Green
• Brown
• Euschistus spp.
• Plant Bugs
• Tarnished
• Clouded
• Leaf-footed Bugs

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Proportion of Green, Brown, and Southern Green
Stink Bugs by Location
North Carolina
South Carolina
Georgia
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Insecticide Susceptibility

• Southern green, green, and brown stink bugs are
  the primary boll feeding bugs in the southeast.
• Damage potential appears similar among species?
• Pyrethroids good control of southern green and
  green but only fair control of brown stink bugs
  (high rates improve control).
• OPs good control of southern green, green, and
  brown.

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Stink Bug Feeding

• Feeds primarily on fruiting structures and
  meristematic tissues (seed and surrounding
  tissues in cotton bolls).
• Physical destruction of seed (lint production
  reduced).
• Introduces or allows entry (wounds) of pathogens
  and decay organisms.

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Cotton Susceptibility to Stink BugsReproductive
Structures
Willrich 2004, Fromme 2000, Greene 2005
Bolls susceptible to stink bug damage for about
25 days past anthesis. Prefer medium sized bolls,
small bolls abscise, larger bolls remain on the
plant.
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External vs Internal Damage
Callous growths form w/i 48 hrs. (Bundy 2000)
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Stink Bug Damage to Bolls Variability
Fiber Quality color grade, length,
uniformity, mic
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Fiber Quality

• Excessive stink bug damage negatively influences
  most fiber quality measures.
• Appears that if we manage stink bugs
  appropriately (i.e. for maximum profit) that
  fiber quality is sufficiently preserved.

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Year End Internal Boll Damage vs. Yield
(treatment means by trial) Georgia and North
Carolina 2005
Assume 1000 lb/acre Range of Slopes
10 20 Low -0.1311 13 26 High
-1.1434 114 229
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Conclusions

• Yield response to percent of year-end bug damaged
  bolls varies.
• Reasons for variability are not fully understood.
• Severity of Damage ( of warts, degree of rot,
  etc.)
• Bug Complex
• Plant Bug vs. Stink Bug
• Spatial / Temporal Distribution of Damage
• Boll Abscission
• Plant Compensation Potential
• Variety
• Environment
• Environment
• Influence how damage manifest itself (boll rots)

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Bug Damage and Boll Rots

• Severe yield loss occurs when pathogens develop
  in bolls.
• Environmental conditions conducive for boll rots.
• Clean bugs vs Dirty bugs

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Cotton Boll Damage Associated with Piercing
Sucking Pests

• Medrano, Esquivel, Bell, and Lopez, USDA-ARS, TX
• Bolls collected from NC, SC, and GA
• Pathogens (bacteria and fungi) identified from
  bug damaged bolls.
• Pathogens present and severity of infection vary
  by location and year.
• Demonstrated transmission of a cottonseed and
  boll rotting bacteria by southern green stink
  bug.
• Resistance to bacterial infections increases with
  boll development.
• 3 weeks post anthesis, similar to boll age
  susceptibility studies??
• Ongoing Research
• Movement of pathogen(s) through the
  insect/understand infection processes.
• Develop a molecular-based tool to detect the
  presence of potential pathogens in the field
  and/or reservoirs.
• Source of pathogens (migration into cotton).

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Multiple Cultivated and Wild HostsLandscape/Farms
cape, Tillman, Mizell, Cottrell, Greene, Blinka,
Toews
Move from one host to another throughout the
growing season (host suitability). -
Forecast populations? - Identify high risk
areas? - Bio Control opportunities? -
Pathogen acquisition?
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Sampling MethodsToews

• observation
• sweep net
• beat cloth or bucket
• pheromone traps
• boll damage

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Scouting / Thresholds

• Internal boll damage is currently our best method
  for determining the need to treat with
  insecticide.
• 20 internal boll damage or 1 bug per 6 row feet.

Sample bolls _at_ the diameter of a quarter.
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Distribution
3 Aug 07

• A 24-acre commercial cotton field was sampled
  weekly at a density of 20 bolls/acre
• Developing bolls were dissected weekly and
  examined for internal damage
• Spatial maps were created to visualize damage

31 Aug 07
9 Sept 07
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Potential of Using External SymptomsBlinka,
Toews, Herbert, Bacheler
Predict internal damage with 90 accuracy when 4
or more external lesions are present.

• Figure 2. External sunken lesions caused by
  stink bug feeding.

Predictability of internal boll damage based on
total external lesions.
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Threshold Trials 2005Heavy Pressure
107 lbs?
N11 locations
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Protective treatments initiated and maintained
weekly. (week of bloom) 1st 2nd
3rd 4th 5th 6th 7th
Number of susceptible bolls per plant varies in
time.
(yield penalty for delaying treatment by 1 week)
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Dynamic vs Static Thresholds

• 20 internal boll damage is a good threshold.
• Adjust up or down based on the number of
  susceptible bolls present.
• Tested a Dynamic Threshold during 2006/2007.
• weeks 3, 4, and 5 of bloom (threshold lowered)
• weeks 1-2, and 6 of bloom (threshold raised)

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Stink Bug Threshold TrialsSE Regional Stink Bug
Project (2006 2007)
10.51
18.00
(10.68)
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58
75
0 Appl.
1.2 Appl.
1.8 Appl.
6.2 Appl.
Net Return 0.65/lb - 9.00/appl.
n16 locations
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Colquitt Co. GA 2005 Scott Brown and Glenn
Beard Untreated 625 lbs/acre Bidrin (4
applic.) 1142 lbs/acre
529
1104
1167
1090
924
886
198
1205
Peanuts other sources
Percent Yield Loss
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Edge Effects (peanut, soybean, corn)Toews
2007
2008
Interaction Plt0.1
Interaction Plt0.1
The current treatment threshold is 20 damaged
bolls
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Innovative Management

• How can these findings be exploited to improve
  cotton pest management?
• Farmscape planning?
• Trap crops?
• Barrier crops?
• In-field border insecticide applications?
• 48 border 18 of field area

25-acre field
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