Lethal, Biological, and Biochemical Impacts of Two Insecticides on the 2nd Instar Larvae of The Fall Armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae)

Document Type : Original Article

Authors

1 Zoology Department, Faculty of Science, South Valley University, Qena, Egypt.

2 General Authority for Veterinary Services, Qena Veterinary Directorate, Qena, Egypt.

Abstract

The fall armyworm Spodoptera frugiperda, a destructive insect pest, poses a significant threat to agricultural crop production, particularly maize. Traditional chemical insecticides have drawbacks, such as resistance building and environmental pollution. Proper selection and understanding of the potential consequences of insecticides are crucial for efficient control. The current study assesses the efficiency of spinetoram as a bioinsecticide compared with chlorpyrifos as an organophosphorus insecticide on the 2nd larval instar of S. frugiperda under laboratory conditions. The LC50 values of chlorpyrifos and spinetoram were 181.0 and 0.23 ppm, respectively, depending on commercial products. The results revealed that the toxicity of chlorpyrifos and spinetoram significantly increased the larval period and decreased the pupation percentage, leading to elevated larval mortality. Both tested insecticides increased pupal durations and decreased pupal weights. Moreover, both spinetoram and chlorpyrifos significantly decreased the mean number of eggs laid. Fundamentally, the two applied insecticides significantly altered carbohydrates and lipids levels; however, spinetoram significantly lowered the total protein level. Furthermore, there is a significant difference in the activity of the digestive enzymes invertase and amylase. The activity of phenoloxidase, glutathione S-transferases, and chitinase were significantly varied. Based on the results, these insecticides offer a broad range of effectiveness in the control of S.  frugiperda, but spinetoram superior chlorpyrifos in some biological and biochemical changes. Spinetoram is a safer, sustainable approach, and more environmentally friendly biocide that can be used instead of chlorpyrifos in integrated pest management strategies for controlling the fall armyworm.

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