Antifeedant and Toxic Effects of a Neem (Azadirachta indica A. Juss)-Based Formulation Neemix® Against Nezara viridula (L.) (Hemiptera: Pentatomidae)

Abstract

The antifeedant activity of Neemix 4.5 EC, a commercial formulation of azadirachtin from the neem tree (Azadirachta indica A. Juss), was tested against adult Nezara viridula (L.) in the laboratory using a cowpea pod-dip method. A toxicity assay was conducted by dipping fourth-instar nymphs. Feeding by adults was significantly reduced in treated pods compared with controls, based on counts of salivary deposits on pod surfaces, inside pod walls and on seeds. The antifeedant effect of azadirachtin was significantly greater on pods treated with 5% aqueous solution than on those treated with 0.5%, indicating that the antifeedant activity was related to concentration. Bugs were initially repelled by Neemix before approaching treated pods to feed. The LC50 for nymphs was 61% (27450 ppm azadirachtin) at 2 d and ranged from 1.8 to 6.2% (810 to 2790 ppm) at 5 d post-treatment, which indicated that neem was slow acting. Sublethal treatment of nymphs disrupted molting and caused morphological defects in adults. Development time to adulthood also was prolonged, and longevity of females was reduced by neem treatments. Azadirachtin may provide an effective component of a comprehensive management program for N. viridula.