Opções de Manejo com Produtos com Diferentes Mecanismos de Ação e Indução de Resistência para Diaspis echinocacti Bouché em Opuntia stricta Haw

Abstract

Forage cactus (Opuntia stricta Haw.) has established itself as one of the main food sources for livestock in the Brazilian semiarid region, especially during dry periods. However, the intensification of cultivation has favored the increase of pests, such as the scale insect (Diaspis echinocacti Bouché), which compromises plant development and productivity. Therefore, the objective of this study was to evaluate whether insecticides with different mechanisms of action and the application of potassium silicate reduce pest infestation and increase crop agronomic performance. In the first experiment, first-instar mobile nymphs were topically exposed to four insecticides (Acetamiprid + Fenpropathrin, Spinetoram, Azadirachtin and Teflubenzuron), in five concentrations each, with mortality assessments at 0, 24, 48, 72, 96 and 120 hours. The mixture of Acetamiprid + Fenpropathrin was the most efficient, with 98% mortality at the highest concentration (4000 ppm), median lethal concentration CL₅₀ of 1530 ppm and median lethal time (LT₅₀) of 48 h. Spinetoram showed 95% mortality and CL₅₀ of 1590 ppm, with a lethal time of 24 h. Azadirachtin reached 88% mortality only at the dose of 32000 ppm, with a longer action. Teflubenzuron was the least efficient, with a lethal time of 72 h. In the second experiment, the influence of potassium silicate doses and application times on scale infestation and palm productivity was evaluated using a supervised machine learning model (Decision Trees) applied at four different times, in addition to a control treatment. The 28 mL L⁻¹ dose provided the best results, with a significant increase in productivity and reduction in infestation, indicating a resistance-inducing effect. The results demonstrate that the integrated use of chemical and nutritional strategies can be highly efficient in the management of scale insects and in increasing the productivity of forage cactus, contributing to more sustainable production systems in the Brazilian semiarid region.