Journal : Crop Protection
Title : Assessment of the impact of insecticides on Anagrus nilaparvatae (Pang et Wang) (Hymenoptera: Mymanidae), an egg parasitoid of the rice planthopper, Nilaparvata lugens (Hemiptera: Delphacidae)
Year : 2008
Volume : 27
Issue : 3
First Page : 514
Last Page : 522
Authors : Wang HuaiYin, Yang Yang, Su JianYa, Shen JinLiang, Gao CongFen, Zhu YuCheng.
Abstract : The parasitoid, Anagrus nilaparvatae (Pang et Wang), is a major natural enemy of the rice planthopper Nilaparvata lugens. It plays an important role in the integrated pest management (IPM) of the rice planthopper, although chemical control is also effective. However, compatibility of biological and chemical control has never been investigated with this system. This study was designed to assess potential insecticide toxicities to the wasps, including acute and residual toxicity through contact and oral ingestion. Fourteen insecticides, including organophosphates, carbamates, pyrethroids, insect growth regulators (IGRs), neonicotine, phenylpyrazole, and antibiotics were selected to test their toxicities against the adult parasitoid. Median lethal concentration (LC₅₀) of each insecticide was first determined. Acute contact toxicity tests indicated that chlorpyrifos had the highest toxicity to the wasp, requiring the least chemical to achieve 50% mortality. Imidacloprid was the second most toxic insecticide, while IGRs had the lowest toxicity. Results of oral toxicity tests of 14 pesticides showed that dichlorvos was the most toxic, which generated 100% mortality only 2h after treatment. Isoprocarb, imidacloprid, and thiamethoxam were the second most toxic insecticides and killed all wasps in a 4-h period. Residual toxicity results indicated that imidacloprid was the most persistent insecticide, and it retained residual toxicity (80.7% mortality) on rice leaves up to 7d after treatment. Thiamethoxam, triazophos, and fipronil also had long residual toxicity to the wasps with 7-d mortalities as 66.8%, 54.6%, and 50.0%, respectively. IGRs showed very low contact and residual toxicity, but exhibited certain chronic effects of oral toxicity on longevity, fecundity, and offspring emergence.
