ryan jackson usda-ars simru

Impact of Fall Armyworm Survival in Bt Crops on

Survival and Damage Potential of Subsequent Generations

Ryan Jackson

USDA-ARS

SIMRU

Fall Armyworm Problem• Sporadic pest

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Fall Armyworm Problem

Egg masses difficult to locate because of location in canopy.

Fall Armyworm Problem

Small fall armyworm larvae feed on leaves, bracts, and flowers.

Fall Armyworm Problem

Larger larvae damage flowers and bolls.

Fall Armyworm Problem

Problem is often identified when large larvae are found in white flowers.

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%

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.

Objective

• Determine whether FAW development on Bt sweetcorn or Bt cotton provides a benefit to subsequent generations in Bt cotton.

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.

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.

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.

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PHY410R PHY470WR

Non-Bt Strain Bt Strain

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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.

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PHY410R PHY470WR

Non-Bt Strain Bt Strain

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cent

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tion

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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.

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PHY410R PHY470WR

Non-Bt Strain Bt Strain

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cent

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tion

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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.

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PHY410R PHY470WR

Non-Bt Strain Bt Strain

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cent

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tion

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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.

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FM9060F FM9063B2F

Non-Bt Strain Bt Strain

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cent

Bol

l Pen

etra

tion

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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.

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10

20

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FM9060F FM9063B2F

Non-Bt Strain Bt Strain

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Percent Survival of 3-d old FAW Larvae Whose Parents Completed Development on NBT or Bollgard II Cotton - 5 d Rating.

Leaf Tissue Bioassay.

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FM9060F FM9063B2F

Non-Bt Strain Bt Strain

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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.