( <i>Z</i> )‐11‐Hexadecenyl acetate acts as an antagonist of the sex pheromone of the rice stem borer <scp> <i>Chilo suppressalis</i> </scp> (Walker)

BACKGROUND: Insect sex pheromones are widely used in pest management because of their high sensitivity and strong species specificity. However, the incorporation of pheromone analogs may modify insect behavioral responses, thereby weakening or improving the control efficacy. The rice stem borer, Chilo suppressalis (Walker), is a major rice pest that is commonly managed using pheromone-based strategies. However, the effects of ester-type pheromone analogs on pheromone communication systems remain insufficiently understood. RESULTS: We examined the effects of incorporating (Z)-11-hexadecenyl acetate (Z11-16:Ac) into a C. suppressalis sex pheromone blend. Electroantennogram recordings showed that Z11-16:Ac elicited antennal responses ranging from 0.06 to 0.22 mV, comparable with those induced by (Z)-13-octadecenal, a minor component of the natural pheromone. Dual-choice behavioral assays revealed that the addition of Z11-16:Ac reduced male attraction to pheromone sources by approximately 22.4 ± 31.8% (mean ± SD, n = 13; 95% confidence interval 3.2-41.7%). Exposure to Z11-16:Ac alone or in combination with the sex pheromone markedly reduced oviposition, with egg numbers reduced by 52-72% relative to untreated controls. Field trapping experiments further demonstrated that Z11-16:Ac consistently inhibited male attraction, with stronger inhibitory effects observed at higher doses. Male attraction was almost completely suppressed at higher doses (>75 μg) and reduced by 47% at lower doses (2.25 μg). CONCLUSION: These results demonstrate that Z11-16:Ac functions as a pheromone antagonist in C. suppressalis. Its consistent inhibitory activity under both laboratory and field conditions highlights its potential application in pheromone-based pest management strategies, including mating disruption and behavioral manipulation, offering an environmentally sustainable approach to controlling this economically important rice pest. © 2026 Society of Chemical Industry.