Reduced Mythimna separata infestation on Bt corn could benefit aphids

Area of Science:

• Agricultural Entomology
• Plant Biotechnology
• Insect Ecology

Background:

• Genetically engineered Bacillus thuringiensis (Bt) crops effectively control lepidopteran pests.
• Non-target herbivores may increase in importance on Bt crops due to altered plant defenses.
• Reduced herbivory can decrease induced plant defensive compounds, potentially benefiting secondary pests.

Purpose of the Study:

• To investigate the effect of reduced damage by Mythimna separata (a caterpillar pest) on aphid populations in Bt corn.
• To compare the performance of Rhopalosiphum maidis (an aphid pest) on Bt and non-Bt corn plants with varying levels of caterpillar infestation.

Main Methods:

• Compared the fitness of Rhopalosiphum maidis on non-Bt corn plants infested with Mythimna separata larvae versus uninfested plants.
• Evaluated aphid nymphal development time, adult longevity, and fecundity.
• Assessed aphid population growth rates on both Bt and non-Bt corn under caterpillar infestation.

Main Results:

• Caterpillar-infested corn plants significantly reduced the fitness of Rhopalosiphum maidis.
• Aphids on infested plants exhibited longer development, reduced longevity, and lower fecundity.
• Aphid population growth rates were significantly lower on caterpillar-infested plants compared to uninfested ones.

Conclusions:

• Reduced Mythimna separata infestation in Bt corn can unexpectedly benefit aphid development.
• Aphids performed better on Bt corn than non-Bt corn when caterpillar damage was minimal.
• Monitoring of aphids and other non-target pests is crucial for Bt corn cultivation in China.