Assessment of the lethal and sublethal effects by spinetoram on cotton bollworm

Abstract

Helicoverpa armigera is an universal pest around the world, which has recovered again in recent years because of the adjustment of cropping structure and resistance to Bacillus thuringiensis (Bt) in China. As a new insecticide spinetoram is extensively used to control many pest insects, including H. armigera. However the lethal and sublethal effects of spinetoram on cotton bollworm have not been assessed. In the present study, the toxicity of spinetoram against cotton bollworm was tested under laboratory conditions. Results demonstrated spinetoram showed an excellent activity against H. armigera, especially, against Bt (Cry1Ac) resistant H. armigera. Treatment with spinetoram at the doses of 0.19 mg/kg and 0.36 mg/kg (LC8 and LC20 after 24h oral exposure) significantly arrested the development of surviving larvae and caused significant decrease in larvae wet weight. Besides, the survivors after spinetoram treatments showed significant reduction of pupation ratio, pupal weight, emergence ratio, longevity and fecundity of adults. At same time, spinetoram treatments resulted in significant increase in the prepupal and pupal periods of survivors. In summary, these results showed that spinetoram could be used as an effective pesticide to control H. armigera, especially Cry1Ac-ressitacne, consequently to take both lethal and sublethal effects to cotton bollworm into consideration in cotton bollworm control strategy.

Effect of sublethal doses of some insecticides and their role on detoxication enzymes and protein-content of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

“…Insecticide resistance in Lepidopteran is a major concern throughout the world because several species of it have been reported to have developed resistance to several classes of insecticides Wei et al (2018). The present study revealed high levels of resistance to profenofos and cyfluthrin in the tested field population; at the same time, emamectin benzoate, spinetoram, and lufenuron showed low levels of resistance.…”

“…Therefore, it was necessary to study the effect of some new insecticides that appeared in the Egyptian market on S. littoralis, in terms of their toxicity and their effect on enzymes that plays a defensive role in changing the response to insecticide in S. littoralis becomes extremely tolerant of the action of insecticides because of the intensive treatments of these insecticides. Therefore, new insecticides with modes of action that differed from conventional insecticide are highly desirable in integrated pest management (IPM) programs among these insecticides are insect growth regulators (IGRs), avermectin, and spinosyn insecticide group (Subramanian and Shankarganesh, 2016;Wei et al, 2018). Different mechanisms of resistance to organophosphate and pyrethroid insecticides have been identified in S. littoralis, including enhanced metabolism, nerve insensitivity, reduced penetration, and target site insensitivity; it is caused by defensive enzymes in the insect (Rong et al, 2017).…”

Comparative Toxicity of Helicoverpa armigera and Helicoverpa zea (Lepidoptera: Noctuidae) to Selected Insecticides

“…has increased in recent years. Spinetoram has been reported to have high efficacy against Helicoverpa species under field conditions [67,68]. Interestingly, spinosad resistance is associated with a reduced fitness, as reflected in prolonged egg, larval, and pupal periods and decreased pupal survival and overall fecundity [66].…”

“…Our results indicated that spinetoram is highly toxic to both Helicoverpa species. This insecticide is considered an important alternative for controlling Helicoverpa pests, especially for Cry1Ac-resistant populations [68]. Xie et al [67] found spinetoram to be effective against H. armigera, inducing high mortality rates and sublethal effects similar to spinosad in H. armigera populations from China [66].…”

“…Visnupriya and Muthukrishnan [75] also reported low LC 50 values for spinetoram on H. armigera, ranging from 1.94 to 5.20 ppm. There have been few reports of Helicoverpa species resistance to spinetoram; nevertheless, if usage patterns and exposure to sublethal concentrations of spinetoram increase, selection for resistance to it is also likely to rise [68].…”