Residual Effects of Some Conventional and Biorational Pesticides on Ladybird Beetle, Adonia variegata Goeze

Abstract

A variety of pesticides is used in lucerne fields to control pests. Biological control agents are also used to control these pests, and therefore it is important to understand the effects of such pesticides on these beneficial insects. The residual effects of Dursban [chlorpyrifos] (48%, EC) and fenvalerate (20%, EC) as conventional pesticides as well as Bio-Fly (100% Beauveria bassiana) and Bio-Neem (azadirachtin, 0.09% multipurpose concentrate) as biorational pesticides on the ladybird beetle, A. variegata [Hippodamia variegata] were studied using panel exposure technique. Dursban was highly toxic to ladybird beetles at 1/2, 1, and 2 folds of the recommended dosage, where mortality percentages ranged from 46.7-50, 50, and 55-55.33%, respectively, from 1 to 120 h. Fenvalerate produced moderately toxic effects on the coccinellids, where mortality percentages were 10-47.7, 20-50, and 13.33-50%, following the residual exposure of 1/2, 1, and 2 folds of the recommended dosage. On the other hand, the biorational pesticides Bio-Neem and Bio-Fly showed slight toxicity (a maximum of 10% mortality), produced after a 5-day exposure of their recommended and half-recommended dosages. When the dose was doubled, the toxicity of Bio-Fly did not increase; however, that of Bio-Neem reached 26.7 after 5 days. It can be concluded that in IPM programmes, the application of conventional pesticides must be considered carefully for use; whereas, biorational pesticides can be used with natural enemies with minimum effects.