Comparative bioactivity of annonaceous derivatives and neonicotinoid-based insecticides against the silverleaf whitefly

Abstract

Bemisia tabaci (Hemiptera: Aleyrodidae) is a polyphagous pest that causes expressive damage on tomato. Spraying with synthetic insecticides is still the main strategy used for whitefly management in tomato production systems; however, the indiscriminate use of these compounds can brings negative impacts on human health and environment besides selecting resistant population, stimulating the search for alternative methods of pest control, including the use of botanical insecticides. Thus, this study evaluated the bioactivity of Annona mucosa, A. sylvatica and A. muricata derivatives and a commercial formulation based on acetogenin annonin (Anosom® 1 EC, 10,000 mg.L−1) compared with the neonicotinoid insecticide thiamethoxam (Actara® 250WG, 250 g.kg−1) on nymphs and adults of B. tabaci under laboratory, greenhouse and field conditions on tomato crops. An initial diagnostic test on nymphs identified ethanolic seed extract at 500 mg.L−1 as the most suitable insecticidal compound. The nymphicidal effect (7 and 10 days after spraying) of ethanolic extracts of Annona mucosa, A. muricata and A. sylvatica (at concentrations of 500; 5,000 and 10,000 mg.L−1) were evaluated relative to negative and positive controls. Because of the pronounced bioactivity of the ethanolic seed extract of A. mucosa (ESAM; majority compound: rolliniastatin-1), this extract was used in the rest of the trials and tests (LC50 and LC90 of 10.83 and 200.24 mg.L−1, respectively). The effects of ESAM (at LC50 and LC90) on adults were evaluated 72 h after spraying, with thiamethoxam and ESAM (LC90) showing the highest control effectiveness (26,93% and 13,46%, respectively). In a greenhouse trial, contact, systemic and translaminar effects of ESAM (at LC50 and LC90) on nymphs were evaluated at 3, 5 and 7 days after application of the treatments. The results indicated that there was a translaminar effect with ESAM (LC90) (31.1% mortality) and a contact effect with Anosom® 1 EC and LC90 of ESAM (84.4 and 94.4% of the control, respectively). In the field, only the contact effect was assessed, with approximately 91% control of the nymphs achieved with both Anosom® 1 EC and ESAM (LC90 previously estimated). Thus, the results of this study demonstrate the potential that Annonaceae derivatives could have for the management of B. tabaci MEAM 1 in organic farming systems.