Use of an artificial diet system to study the toxicity of gut-active insecticidal compounds on larvae of the green lacewing Chrysoperla sinica

A semi-liquid artificial diet was established and found to be a suitable food source for Chrysoperla sinica larvae, comparable to aphid prey. Using the artificial diet, we established and validated a dietary exposure assay by using the insecticidal potassium arsenate (PA) as positive control. Dose-dependent responses were documented for all observed life-table parameters of C. sinica larvae such as survival rate, pupation rate, larval weight, and larval development time. Thus, the dietary assay can detect the effects of insecticidal compounds on the survival and development of C. sinica larvae. Using the established dietary assay, we subsequently tested the toxicity of Cry1Ab, Cry1Ac, and Cry2Aa proteins (which are produced by transgenic maize, cotton or rice plants) to C. sinica larvae. Artificial diets containing Galanthus nivalis agglutinin (GNA) or PA were included as positive controls. Survival and development of C. sinica larvae were not affected when the artificial diet contained purified Cry1Ab, Cry1Ac, or Cry2Aa at 200 μg/g diet. In contrast, C. sinica larvae were adversely affected when the diet contained PA and GNA. The stability and bioactivity of the Cry proteins in the diet and Cry protein uptake by the lacewing larvae were confirmed by bioassay with a Cry-sensitive insect species and by ELISA. The current study describes a suitable experimental system for assessing the potential effects of gut-active insecticidal compounds on green lacewing larvae. The experiments with the Cry proteins demonstrate that C. sinica larvae are not sensitive to Cry1Ab, Cry1Ac, and Cry2Aa.