Topical and field‐tested residual effects of globally used insecticides on the parasitoid Tamarixia radiata released against the Asian citrus psyllid, Diaphorina citri

Abstract

Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae) is the key parasitoid of the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), in several citrus‐producing regions of the world. Chemical control is common to suppress ACP. Insecticides from globally used classes of insecticides for controlling ACP were tested on its primary parasitoid, T. radiata. Evaluations included dose–response of dimethoate, fenpropathrin, and imidacloprid in a topical application and lethal and sublethal effects from residues of imidacloprid, fenpropathrin, horticultural mineral oil (HMO), pyrethrin, and spirotetramat at 1, 3, and 7 days after application (DAA) of sprays on citrus trees in the orchard. The parasitism potential of the females that survived insecticide exposure was evaluated on untreated nymphs of ACP developing on citrus shoots and untreated parasitoid females were evaluated on nymphs treated with insecticides. In the topical application, imidacloprid was 8× more toxic to T. radiata than dimethoate and fenpropathrin. The lethal effect of the residues from imidacloprid and fenpropathrin sprays was more detrimental than other insecticides. Parasitoid mortality from 1‐ to 3‐day‐old residues averaged 90–96% for imidacloprid, 83–94% for fenpropathrin, 38–77% for pyrethrin, 43–44% for HMO, and 17–33% for spirotetramat. Parasitism by females that survived insecticide exposure was reduced by 71–88% from fenpropathrin, 28–59% from pyrethrin, 31–55% from imidacloprid, 44–4% from spirotetramat, and 39–11% from HMO compared to untreated females. The lethal and sublethal effects of all insecticides on T. radiata were significantly reduced at 7 DAA, suggesting a lower impact on its establishment and performance if releases are made after a week from spray application.