Baseline toxicity and ovicidal action of different insecticides on new invasive insect pest into India: Fall armyworm, Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae)

Abstract Fall armyworm (Spodoptera frugiperda) (J.E. Smith) is a recent and invasive destructive insect pest of corn and other major crops of India; if left uncontrolled, it can destroy a crop totally. The pest carries history of resistance to many insecticides from its nativity and spread across the globe. It is likely to bear and /or develop resistance to a range of insecticides presently being used for its management in India, a possibility that has to be monitored regularly. The egg, being the first stage of the pest’s life cycle, is ideal for controlling its proliferation, and assessing the toxicity of different pesticides to eggs and larvae, and resistance, if any, to the pesticides is important for baseline studies. Accordingly, the present study assessed with common pesticides. In terms of their larvicidal action 72 h after application, chlorantraniliprole was found to be the most toxic, followed, in that order, by emamectin benzoate, flubendiamide, spinetoram, Spinosad, and azadirachtin. That order changed when the insecticides were tested for ovicidal action: thiodicarb was the most toxic, followed by spinetoram. Mortality was the highest in 3-day-old eggs, higher than that recorded in 1- or 2-day-old eggs and higher at the recommended doses than at half the recommended doses. Such differences in the target – larvae or eggs – are crucial to devising effective strategies for controlling insect pests. The strategies will be even more effective if the mechanism of action of the newer insecticides is elucidated.