Ovicidal and neonate-killing activities of commonly used insecticides on the rice striped stem borer (Chilo suppressalis).

BACKGROUND

The rice striped stem borer (SSB), Chilo suppressalis, a major pest in rice cultivation, presents a management challenge because of increasingly prevalent resistance to insecticides. Controlling pests during the egg stage is critical for preventing crop damage; however, most insecticides target the larvae. In the present study, we evaluated the ovicidal and neonate-killing effects of 21 insecticides on SSB eggs and neonatal larvae.

RESULTS

The ovicidal activities of diflubenzuron and phoxim, which effectively reduced egg hatching rates, were the highest: 98.26% and 93.40% at 500 mg/L and 71.86% and 69.42% at 100 mg/L, respectively. Spinosyns and ivermectins exhibited high neonate-killing toxicity, at 500 and 100 mg/L applications at the egg stage, respectively, with almost 100% neonate larvae mortality, thereby effectively targeting neonates before they entered the rice stems. However, two insect growth regulators, pyriproxyfen and lufenuron, which are effective against the eggs of other species, were less effective against SSB eggs. In addition, we observed that insecticide sensitivity decreased with SSB egg development, highlighting the importance of targeting younger eggs. Population-specific variation was also observed in the susceptibility of the eggs to spinetoram, with the highest ovicidal rates observed for the Yongxiu and Chongren populations.

CONCLUSION

This study highlights the importance of early-stage pest control in SSB and the need for developmental-stage-focused and population-specific management strategies. These findings support the incorporation of ovicidal and larvicidal insecticides into integrated pest management approaches to increase pest control efficacy. © 2025 Society of Chemical Industry.