impact of fall armyworm survival in bt crops on survival and damage potential of subsequent...
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![Page 1: Impact of Fall Armyworm Survival in Bt Crops on Survival and Damage Potential of Subsequent Generations Ryan Jackson USDA-ARS SIMRU](https://reader036.vdocuments.us/reader036/viewer/2022081512/5697c0221a28abf838cd36fb/html5/thumbnails/1.jpg)
Impact of Fall Armyworm Survival in Bt Crops on
Survival and Damage Potential of Subsequent Generations
Ryan Jackson
USDA-ARS
SIMRU
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Fall Armyworm Problem• Sporadic pest
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Fall Armyworm Problem
Egg masses difficult to locate because of location in canopy.
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Fall Armyworm Problem
Small fall armyworm larvae feed on leaves, bracts, and flowers.
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Fall Armyworm Problem
Larger larvae damage flowers and bolls.
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Fall Armyworm Problem
Problem is often identified when large larvae are found in white flowers.
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Fall Armyworm Problem• In mid-South and southeastern states, >80% of
cotton planted to Bt varieties.• Bt varieties have limited activity against FAW.• Cage studies have shown that Bt cottons reduce
FAW boll damage below that of non-Bt cotton:– Bollgard – 29-30%– Bollgard II – 33-53%– WideStrike – 48-56%
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Fall Armyworm Problem
• Field corn is a primary host of FAW.
• Acreage of Bt corn is increasing annually.
• Laboratory studies have shown that FAW survival on Bt field corn lends to increased survival of subsequent generations on Bt cottons.
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Objective
• Determine whether FAW development on Bt sweetcorn or Bt cotton provides a benefit to subsequent generations in Bt cotton.
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MethodsBloom Cages
• Collected FAW larvae from Bt and non-Bt sweetcorn.
• Reared FAW on appropriate tissues through larval stage.
• Infested five 2-d old or one 5-d old F1 larvae onto 40 white flowers of non-Bt, Bollgard II, and WideStrike and caged.
• Rated small bolls for damage after 7 d.
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MethodsLeaf Tissue Bioassay
• Collected FAW larvae from Bollgard II and non-Bt cotton.
• Reared FAW on appropriate tissues through larval stage.
• Infested five 3-d old F1 larvae onto 20 leaves of FM9063B2F and FM9060F in leaf tissue bioassays.
• Larval survival ratings made after 5 d.
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Percent Boll Penetration by 2-d old FAW Larvae Whose Parents Completed Development on NBT or Bt Corn - 7 d Rating.
Bloom Cages – Test 1.
0
10
20
30
40
50
60
70
PHY410R PHY470WR
Non-Bt Strain Bt Strain
Per
cent
Bol
l Pen
etra
tion
a
b
aa
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Percent Boll Penetration by 2-d old FAW Larvae Whose Parents Completed Development on NBT or Bt Corn - 7 d Rating.
Bloom Cages – Test 2.
0
10
20
30
40
50
60
PHY410R PHY470WR
Non-Bt Strain Bt Strain
Per
cent
Bol
l Pen
etra
tion
a
b
aa
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Percent Boll Penetration by 5-d old FAW Larvae Whose Parents Completed Development on NBT or Bt Corn - 7 d Rating.
Bloom Cages – Test 1.
0
10
20
30
40
PHY410R PHY470WR
Non-Bt Strain Bt Strain
Per
cent
Bol
l Pen
etra
tion
a
a a a
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Percent Boll Penetration by 5-d old FAW Larvae Whose Parents Completed Development on NBT or Bt Corn - 7 d Rating.
Bloom Cages – Test 2.
0
10
20
30
40
50
PHY410R PHY470WR
Non-Bt Strain Bt Strain
Per
cent
Bol
l Pen
etra
tion
a
b aa
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Percent Boll Penetration by 2-d old FAW Larvae Whose Parents Completed Development on NBT or Bt Corn - 7 d Rating.
Bloom Cages.
0
10
20
30
40
FM9060F FM9063B2F
Non-Bt Strain Bt Strain
Per
cent
Bol
l Pen
etra
tion
a
a a a
![Page 17: Impact of Fall Armyworm Survival in Bt Crops on Survival and Damage Potential of Subsequent Generations Ryan Jackson USDA-ARS SIMRU](https://reader036.vdocuments.us/reader036/viewer/2022081512/5697c0221a28abf838cd36fb/html5/thumbnails/17.jpg)
Percent Boll Penetration by 5-d old FAW Larvae Whose Parents Completed Development on NBT or Bt Corn - 7 d Rating.
Bloom Cages.
0
10
20
30
40
50
FM9060F FM9063B2F
Non-Bt Strain Bt Strain
a
a
aa
![Page 18: Impact of Fall Armyworm Survival in Bt Crops on Survival and Damage Potential of Subsequent Generations Ryan Jackson USDA-ARS SIMRU](https://reader036.vdocuments.us/reader036/viewer/2022081512/5697c0221a28abf838cd36fb/html5/thumbnails/18.jpg)
Percent Survival of 3-d old FAW Larvae Whose Parents Completed Development on NBT or Bollgard II Cotton - 5 d Rating.
Leaf Tissue Bioassay.
0
10
20
30
40
50
60
70
80
90
FM9060F FM9063B2F
Non-Bt Strain Bt Strain
Per
cent
Su
rviv
al
a a
a a
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Summary• When fed non-Bt cotton, FAW appeared to have a
fitness cost associated with development on Bt sweetcorn but not Bollgard II cotton.
• Survival on Bt sweetcorn provided no advantage for subsequent generation on WideStrike cotton.
• Survival on Bollgard II cotton also provided no advantage for subsequent generation on Bollgard II cotton.
• Additional studies need to be conducted with FAW colonies from Bt field corn.
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