Acaricidal activity and efficacy of oxymatrine-based biopesticide against peanut red spider mite

The acaricidal activity and efficacy of oxymatrine-based commercial biopesticide on the peanut red spider mite Tetranychus ogmophallos Ferreira and Flechtmann, 1997 were assessed under laboratory, semi-field, and field conditions. In the laboratory, the oxymatrine-based biopesticide provided high acute toxicity for T. ogmophallos larvae, protonymphs, deutonymphs, and adult females, in a manner dependent on the concentration, developmental stage, and exposure time of mites to residues. Among the mite developmental stages, T. ogmophallos larvae were more susceptible to the biopesticide than adult females. The biopesticide also reduced fecundity and fertility, induced a low ovicidal effect, and provided a high repellent activity against T. ogmophallos. In semi-field, the biopesticide showed a short biological persistence [mortality >80% up to 1 day after spraying (DAS)] compared to the synthetic acaricide fenpropathrin (mortality >80% up to 3 DAS). At 7 and 10 DAS, no significant mite mortality was observed on peanut plants treated with biopesticide compared to the control. However, the synthetic acaricide fenpropathrin caused mortality greater than 40% up to 10 DAS. In the field, the biopesticide showed high effectiveness in controlling the mite population, with a similar efficacy to the synthetic acaricide fenpropathrin. Therefore, the oxymatrine-based biopesticide constitutes an important management tool to be used in rotation with synthetic acaricides for population suppression of T. ogmophallos in conventional peanut crops or as an effective measure for controlling peanut red spider mite in organic peanut crops.