Evaluation of the effectiveness of natural insecticides on the Colorado Potato Beetle Leptinotarsa Decemlineata (Say)

Abstract

The objective of this study was to evaluate the efficacy of 3 bio-insecticides, spinosad, azadirachtin and Beauveria bassiana, against Colorado potato beetle and the effects on defoliation, potato yield, grade and dry matter. The reference insecticide was thiacloprid and water was the control. The efficacy was assessed 2 and 7 days after crop spraying, through the number of beetle larvae stages L1-L3 and L4 on the plants and the percentage of mortality. The experiment was completed randomized with 4 repetitions. Spinosad presented the highest efficacy (> 97% mortality) similar to the thiacloprid, while the azadirachtin and B. bassiana were effective against both larvae stages only 7 days after crop spraying (65 a 77% mortality). Potato crop yield was similar for the 3 bio-insecticides and for the thiacloprid (mean 17.5 t ha^-1) and lower in the control (10.5 t ha^-1). The study showed the feasibility of the bio-insecticides in crop protection programs, to use in alternation as a resistance strategy.