Control of two-spotted spider mites with neem-based products on a leafy vegetable

Abstract

Neem-based pesticides can be a valuable tool to control the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), in leafy minor crops that lack pest management options and often have pesticide level residues reported. We evaluated the efficacy of three commercially available neem-based products in controlling T. urticae populations on parsley plants. We calculated the concentration-response curves to evaluate the lethal effect of the products on T. urticae and the population level effects of the products by calculating the instantaneous rate of T. urticae population increase. A bioassay in a greenhouse using potted parsley plants was performed to evaluate product efficacy over time and the evolution of phytotoxicity symptoms. The lethal effects varied among products, indicating that formulation may play a role in product efficacy. All products presented sublethal effects on T. urticae populations, which reduced the mite population. However, product efficiency was below 80% and slight symptoms of phytotoxicity were observed, especially when products were applied at high concentrations. Our study revealed the importance in evaluating several components of botanical pesticide effects besides the lethal effects, and it can be used as a simple framework to select botanical pesticides to be used on minor crops such as parsley.