Ecological Effects of Transgenic Crops: Non-target Effects in Bt Cotton

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Ecological Effects of Transgenic Crops
Non-target Effects in Bt Cotton
This presents the results of research only.
Mention of a proprietary product does not
constitute endorsement or recommendation for its
use by USDA.

• Steven E. Naranjo
• USDA-ARS Phoenix, Arizona
• Peter C. Ellsworth
• University of Arizona, Maricopa, Arizona

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Pest Complex - Western U.S. Cotton
Key Pests
Sporadic and Minor Pests
Cotton bollworm Tobacco budworm Armyworms Loopers
Cotton leafperforator Saltmarsh
caterpillar Cutworms Fleahoppers Plant
bugs Stink bugs Cotton aphid Thrips Spider mites
Pectinophora gossypiella
Bemisia tabaci
Lygus hesperus
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Insecticide Use PatternsArizona Cotton
Bt cotton Insect growth regulators
Ellsworth and Jones 2000
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Selective Insecticide UseArizona Cotton
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Natural Enemy Complex -Western U.S.
Parasitoids
Predators
30 species Hyposter Copidosoma Microplitis Lysip
hlebus Chelonus Lespesia Eretmocerus Encarsia Anap
hes Leiophron
50 species Geocoris Orius Nabis Zelus Collops Hi
ppodamia Drapetis Chrysoperla Labidura Misumenops
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Natural Enemies Pectinophora gossypiella
Predators ?23 species described 9 species
(immunological ID)
Parasitoids 4 native species described (rare) 16
exotic species introduced (0 established)
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Non-Target Effects (Arthropods)
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General MethodsNon-target abundance/diversity

• Replicated experimental studies at MAC
• Treatments
• Bt cotton / conventional cotton
• Unsprayed for any pest
• Insecticides for all pests as needed
• Sampling by sweep nets, beat buckets, whole
  plants, pitfall traps
• ANOVA, EstimatorS V. 5 (Colwell) for diversity
  analyses

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Natural Enemy Abundance
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Natural Enemy AbundanceNo Insecticides
4530
5611
1999
0.28
0.40
0.34
0.03
0.98
0.37
0.24
0.57
0.08
0.39
2000
0.89
0.18
0.66
0.70
0.16
0.23
0.16
0.51
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Natural Enemy AbundanceNo Insecticides
P 0.18
P 0.29
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Natural Enemy AbundanceInsecticides as Needed
(e.g. 1999)
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Arthropod Community Structure
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Community Structure Pitfall Traps(Bt vs.
Non-Bt)
68
70
57
57
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Community Structure Pitfall Traps(Sprayed vs.
Unsprayed)
68
69
74
40
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Natural Enemy Function
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MethodsNatural Enemy Function

• Replicated experimental studies at MAC
• No insecticides
• Estimate rates of predation and parasitism

• Sentinel pink bollworm egg masses (20 per plot)

• Life tables for whitefly nymphs (50 per plot)

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Natural Enemy FunctionPredation on Pink Bollworm
Eggs
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Natural Enemy FunctionMortality of Whitefly
Nymphs
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Conservation Biological ControlAn Example
Whitefly IPM in Cotton
Natural Enemies
Bt Cotton
IGRs
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Impact of Conservation
1997
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Thanks to
Virginia Barkley Kim Beimfohr Becci Burke Melanie
Charney Scott Davis
Ghislaine Majeau Ruben Marchosky Greg
Owens Jeffrey Rivas Doug Sieglaff