|
Abstract
|
The toxicity of hexaflumuron and indoxacarb was determined against 3rd instar larvae of H. armigera by the insecticide-incorporated artificial diet method under laboratory conditions. Based on LC50 values, hexaflumuron and indoxacarb were highly toxic against 3rd instar H. armigera. The LC50 values of hexaflumuron and indoxacarb were 6.9 and 9.1 μg a.i. ml−1, respectively. The sublethal effects of hexaflumuron and indoxacarb were investigated by exposing 3rd instar larvae to LC30 concentrations of these insecticides. Sublethal exposure decreased food consumption and larval weight in comparison to control larvae. Specifically, diet consumption and larval weight decreased by 37.2% and 55.5% at 72 h post hexaflumuron exposure, respectively; and by 71.6% and 95.5% at 72 h post indoxacarb exposure, respectively. Additionally, sublethal exposure to the tested insecticides significantly increased larval and pupal developmental times; and reduced pupal weight, pupation rate, and adult longevity in comparison to control insects. Sublethal exposure also adversely affected the levels of glucose, triglyceride (TAG), and protein in comparison to control insects. Furthermore, the number of eggs laid per female and egg hatch rate were negatively affected by the tested insecticides. Larvae exposed to LC30 concentrations of the tested insecticides showed increased glutathione S-transferase (GST) activity at 24 h post-treatment, whereas they showed reduced carboxylesterase (CarE) and GST activities at 72 h post-treatment. Although elevated GST and CarE activities may play some role in the detoxification of indoxacarb and/or hexaflumuron, they were unable to completely suppress indoxacarb and hexaflumuron toxicity against H. armigera. In conclusion, hexaflumuron and indoxacarb will likely negatively alter the population dynamics of H. armigera, and have high potential in integrated pest management of this insect.
|