Combined use of Chrysoperla rufilabris (Neuroptera: Chrysopidae) and Cry3Aa for improved control of Leptinotarsa decemlineata (Coleoptera: Chrysomelidae)

Abstract

The Colorado potato beetle (CPB, Leptinotarsa decemlineata (Say)) is the most important defoliator of solanaceous crops. Control of this pest is hindered by its ability to develop resistance to insecticides, including insecticidal proteins from Bacillus thuringiensis (Bt) Berliner. Therefore, it is important to find alternative tools that may be combined into an integrated pest management approach for CPB control. In this study, we evaluated the efficiency of the combined use of the Cry3Aa protein from Bt and Chrysoperla rufilabris (Burmeister) in controlling CPB. Control of CPB larval second instar at different densities by 3 larval instars of the predator was tested in potato leaves treated with an LC50 concentration of the Cry3Aa protein. Potato leaf damage was evaluated in experiments where CPB larvae were fed with leaves treated with Cry3Aa protein and exposed to predator larvae for 7 days or until all CPB larvae were dead. Results show that all 3 instars of the predator presented a type II functional response for all conditions evaluated. The first and second larval instars of C. rufilabris larvae attacked twice the number of prey (1.34-2.91 and 2.9-4.75, respectively) when CPB larvae were fed on leaves with the Cry3Aa protein. A complete reduction in the number of CPB larvae and lower levels of potato leaf damage was observed when the predator larvae were present. These results support the combined use of the Cry3Aa protein with C. rufilabris in increasing the efficiency of CPB control.