Topical exposure to (E)-β-farnesene alters behavior, reproduction, and wing dimorphism in the English grain aphid, Sitobion avenae (Hemiptera: Aphididae).

(E)-β-farnesene (EβF), a sesquiterpene widely recognized for its role in aphid alarm signaling, triggers escape behaviors and influences aphid population dynamics. Despite its potential as a biological control agent, the effects of EβF on the English grain aphid Sitobion avenae (Fabricius) (Hemiptera: Aphididae), a major wheat pest, remain insufficiently explored. In this study, we topically applied EβF at a concentration gradient (10 to 1,000 ng/μl) to various developmental stages of S. avenae and assessed their behavioral responses, development, reproduction, and winged offspring ratio under different population densities. Our results revealed that EβF at 10 ng/μl induced significant behavioral changes, including leg shaking, fast walking, and falling from host plants, across all developmental stages. Exposure to 200 ng/μl EβF significantly reduced fecundity by 19.6% and shortened lifespan by 17.8%, while increasing the proportion of winged offspring by 19.8%, particularly under low parental density combined with high offspring density. Field trials further revealed that a higher concentration of EβF (1,000 ng/μl) led to a 25% increase in the proportion of winged offspring compared to controls, with environmental factors such as population density influencing the response. These findings confirm the insecticidal and density-dependent effects of EβF on S. avenae, with transgenerational impacts on wing dimorphism, highlighting its potential for the sustainable aphid control in wheat ecosystems.