Twaibu to Discuss Toxicity of Insecticides to Pests That Infest Corn

submitted

Amina Twaibu is a graduate student in Neel Joshi's lab in the Department of Entomology and Plant Pathology.

The Department of Entomology and Plant Pathology is hosting seminar speaker Amina Twaibu, a graduate student in Neel Joshi's lab, today. The seminar is titled, "Toxicity of Different Insecticides to Sitophilus oryzae, Tribolium castaneum, and Tribolium confusum Infesting Corn."

The seminar takes place at 1:30 p.m. today, Friday, July 21, via Zoom.

• Meeting ID: 830 126 2880
• Passcode: email enpl@uark.edu

The seminar is open to everyone.

Twaibu describes the research:

"Corn is an important cereal crop cultivated across various countries, including the United States. Corn serves multiple purposes such as human and livestock food and raw material for industrial processes. Despite being an important crop, corn production faces challenges due to factors such as weather fluctuations and the presence of insect pests and diseases, both in the field and during storage. Among these challenges, insect infestation poses a major threat, as the insect damage not only reduces the quantity and quality of the grain but also renders it unfit for human and animal consumption, leading to a decrease in market value. This research examined the toxicity of four different insecticides, namely, pirimiphos- methyl, deltamethrin, deltamethrin plus (S)-methoprene and malathion against Sitophilus oryzae, Tribolium castaneum and Tribolium confusum, infesting corn. The toxicity of each insecticide was determined in terms of LC50 by exposing target pests at different doses, and the mortality was observed at 24 to 96 hours of exposure as well as until 10 days to determine delayed mortality. In the first study, toxicity of the aforementioned insecticides to S. oryzae was evaluated, and the results revealed that pirimiphos-methyl insecticide was more toxic to S. oryzae, followed by malathion, deltamethrin and deltamethrin plus (S)-methoprene. In the second study, the toxicity of these insecticides was determined for T. castaneum and T. confusum. The results indicated that deltamethrin plus (S)-methoprene and deltamethrin displayed the highest toxicity against T. castaneum, followed by pirimiphos-methyl. On the other hand, pirimiphos-methyl was highly toxic among all the insecticides, followed by deltamethrin plus (S)-methoprene, deltamethrin and malathion against T. confusum. Although these two pests are closely related species, their susceptibility to the selected insecticides was different in such a way that T. confusum displayed higher susceptibility to pirimiphos-methyl compared to T. castaneum while T. castaneum exhibited greater susceptibility to deltamethrin, deltamethrin plus (S)-methoprene and malathion compared to T. confusum. Compared the label recommended application rate with the LC50 found in the study, deltamethrin plus (S)-methoprene and malathion for T. confusum were appropriate and did not require any changes, while the recommended label rate for pirimiphos-methyl exceeded the LC50 value for both species of flour beetles. These findings contribute to our understanding of insecticide toxicity to these stored-grain pests and provide valuable insights for their management."

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