Lethal effects of selected novel pesticides on immature stages of Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

BACKGROUND Trichogramma pretiosum Riley is an important egg parasitoid and biological control agent of caterpillar pests. We studied the acute toxicity of 20 pesticides (14 insecticides/miticides, three fungicides and three herbicides) exposed to recommended field rates. Egg, larval, and pupal stages of the parasitoid in their hosts were dipped in formulated solutions of the pesticides and evaluated 10 days later for percentage of host eggs with holes, number of parasitoids emerged per egg with holes, and stage‐specific mortality of immature as well as adult wasps within the host eggs. RESULTS Seven insecticides (buprofezin, chlorantraniliprole, spirotetramat, flonicamid, flubendiamide) and miticides (spiromesifen, cyflumetofen), one herbicide (nicosulfuron), and three fungicides (myclobutanil, pyraclostrobin, trifloxystrobin + tebuconazole) caused no significant mortality to immature stages or pre‐emergent adult parasitoids relative to controls. By contrast, seven insecticides/miticides (abamectin, acetamiprid, dinotefuran, fipronil, novaluron, spinetoram, tolfenpyrad) adversely affected immature and pre‐emergent adult T. pretiosum, with tolfenpyrad being particularly lethal. Two herbicides had moderate (glufosinate ammonium) to severe (s‐metolachlor) acute lethal effects on the immature parasitoids. CONCLUSIONS This study corroborates earlier findings with adult T. pretiosum. Over half of the pesticides – and all the fungicides – tested in the current study would appear to be compatible with the use of T. pretiosum in integrated pest management programs, with respect to acute parasitoid mortality. © 2017 Society of Chemical Industry