Lethal and sublethal effects of three insecticides on first instar larvae of green lacewing, Chrysoperla carnea, Stephens

Abstract

The green lacewing, Chrysoperla carnea, Stephens (Neu.: Chrysopidae) is one of the most important predators for insect pests such as whiteflies, thrips, psyllids and aphids that ignificantly decrease their populations. In the current study, lethal (LC50) and sublethal effects (LC30) of three insecticides; clothianidin, tebufenozide and flupyradifurone on first instar larvae of C. carnea (<one-day old) and their biological characteristics were evaluated using fertility life table method. Bioassays were conducted by contact method with glass petri-dishes (10 cm diameter). All experiments were conducted at controllable conditions of 25 ± 1 C°, 60 ± 5% and a photoperiod 16:8 h (L:D). The results revealed that LC50 for clothianidin, tebufenozide and flupyradifurone were 8.55, 336.12 and 642.02, respectively. Moreover, the life table response experiment shows that the values of rm and R0 due to LC30 for clothianidin, tebufenozide and flupyradifurone were 0.13, 0.13 and 0.15 per day and 95.72, 97.00 and 136.27 offspring, respectively. At the same time, rm and R0 in the control group were 0.15 per day and 143.26 offspring. Furthermore, the highest survival rate of C. carnea was observed in tebufenozide (54 days) but after control treatment, the lowest survival rate was related to clothianidin (46 days). Results reveal that longevity and life span of both sexes in three treatments were different from the control. According to the IOBC-system, comparing the total effects indicated that clothianidin (77.83%) was classified as slightly harmful while tebufenozide (20.43%) and flupyradifurone (12.89%) were categorized as harmless classes. Hence, based on obtained results, it can be concluded that flupyradifurone than clothianidin are harmless while tebufenozide is less hazardous on C. carnea population. We also measured the esterase enzyme activities of the C. carnea as biomarkers of sublethal exposure to insecticides. The results showed that alpha and beta-esterase activity in treated insects with clothianidin and flupyradifurone was increased (compared to the control), while the enzymatic activity was reduced in insects with tebufenozide treatment.