Laboratory evaluation of the larvicidal effect of cashew balm and three vegetable oils based on the insecticidal plant's Tephrosia purpurea, Ricinus communis, and Thevetia neriifolia for the management of Helicoverpa armigera (Hübner) (Lepidoptera: Noctui

Abstract

Market gardeners use synthetic pesticides in an unreasonable and uncontrolled way to protect their plots from insect pests. With the aim of finding alternative control methods to synthetic products, the efficacy of Cahew Nut Shell Liquid (CNSL) cold-applied Cahew Nut and three vegetable oils based on Tephrosia purpurea, Ricinus communis, and Thevetia neriifolia plants was compared to that of a synthetic insecticide (Lambdacyhalothrin) and to that of a botanical reference pesticide (Topbio). Two experiments were carried out in this study. In the first experiment, the products were tested on the L2 stage of Helicoverpa armigera, with doses of 50, 25, 10, 5, 3, and 1% of each of the plant products. In the second experiment, the same plant products were tested on the L3 stage of the same insect with the same doses of the first experiment, compared to the reference control Lambdacyhalothrin at doses of 10, 5, 3, 2.1, and 0.5% in both experiments. Variables measured were larval mortality, pupae formation, and adult emergence. The LD50s were determined according to the Cox regression model. The results showed that vegetable oils and cashew balm are promising biopesticides for the management of H. armigera populations. Mortality and pupae formation rates varied with dose. For all products used, regardless of the larval stage of H. armigera, a significant difference was observed between the applied doses. Cashew balm and the three vegetable oils are positioned as alternatives to synthetic pesticides that can be used in market gardening.