Effects of toxins from two strains of Verticillium lecanii (Hyphomycetes) on bioattributes of a predatory ladybeetle, Delphastus catalinae (Col., Coccinellidae)

The aim of this study was to test the hypothesis that the whitefly (Bemisia tabaci; Hom., Aleyrodidae) predator ladybird beetles, Delphastus catalinae (Col., Coccinellidae), are not adversely affected in the field by the crude insecticidal toxins extracted from two strains of the fungus Verticillium lecanii, V3450 and Vp28. We developed a method to evaluate sublethal toxicity and its effects on consumption and functional response of D. catalinae. The crude toxins have low toxicity against beetle larva with LC50 values of 1942 (1393–2710) and 2471 (1291–4731) p.p.m., respectively (approximately 10‐ and 12‐fold of field rate of application 200 p.p.m.). The adult beetles had less sensitivity to crude toxins with LC50 values of 4260 (3376–5375) and 4426 (1734–11298) p.p.m., respectively (approximately 20‐ and 22‐fold of field rate 200 p.p.m.). The consumption and foraging capacity were significantly impaired especially in the second‐instar larval beetles which took longer time (more than twice of the control beetles) to consume whitefly eggs after exposure to toxins, although D. catalinae suffered no significant effect on fecundity and longevity, when exposed to a toxin dilution of field rate. The data suggest that spraying of V. lecanii or its toxins should be avoided in the field having immature stages of D. catalinae.