Lethal and parasitism effects of selected novel pesticides on the immature stages of Trichogramma chilonis (Trichogrammatidae: Hymenoptera)

Selectivity of pesticides to the natural enemies in an agroecosystem is required for more effective integrated pest management. Trichogramma chilonis (Ishii) is an important natural enemy of lepidopteran pests, and is often exposed to pesticides. Effects of selected pesticides on acute mortality and parasitism when applied to parasitoids in egg, larval and pupal stages in their hosts were evaluated at 1x (field dose in Pakistan), 2x (double field dose) and 0.5x (half of field dose) doses. The parasitized host eggs were dipped in formulated solutions of pesticides when parasitoids were in different life stages. Parasitoid emergence from hosts treated with acetamiprid, fipronil and abamectin in the egg treatment and with spinetoram in all immature treatments were ≤ 33.9%. Treatment with acetamiprid (≤ 83.1 and ≤ 60.9%), fipronil (≤ 42.3and ≤ 72.7%), and abamectin (≤ 17.2 and ≤ 52.6%) yielded emergence in larval and pupal stage treatments, respectively. Spirotetramat, chlorantraniliprole, spiromesifen, haloxyfop-p-methyl, bispyribac sodium, nicosulfuron, chlorothalonil + procymidone, myclobutanil, pyraclostrobin + metiram, and trifloxystrobin + tebuconazole produced parasitoid emergence ≥ 80.1%. Parasitoids emerged from hosts treated with spirotetramat, chlorantraniliprole, spiromesifen, bispyribac sodium, pyraclostrobin + metiram and trifloxystrobin + tebuconazole (except at 2 × dose in egg treatment) produced ≥ 84% parasitism in all treatments. Myclobutanil treatment of egg, and nicosulfuron and haloxyfop-p-methyl treatments of larvae and pupae, yielded > 90% parasitism. Acetamiprid and fipronil treatment of larvae and pupae, and abamectin treatment of pupae produced ≤ 78.46% and ≤ 10.76% parasitism, respectively. Over half of the pesticides caused no significant mortality to immature stages or exhibited little to no adverse impacts on parasitism and are promising for integration with these parasitoids.