Evaluating botanicals to control maize weevil (Coleoptera: Curculionidae) in stored sorghum grain
Abstract: Insects damage 5-35% of stored grain worldwide, especially in the tropics. Maize weevil, Sitophilus zeamais Motschulsky, causes most damage to stored grain. Control of maize weevil in stored products relies on insecticide use. Alternatives such as inexpensive and eco-friendly botanicals are needed to effectively manage this pest and reduce pesticide residue in food. The objective was to evaluate effects of botanicals to control maize weevil in stored sorghum, Sorghum bicolor (L.) Moench. Evaluated were powders of neem bark, Azadirachta indica; mesquite pods, Prosopis glandulosa var. glandulosa; milkweed leaves, Asclepias speciosa; and a check (no plant powder). Weevils were exposed at 2-day intervals to three doses of each botanical separately to assess the number killed compared with the check. Percentage loss of grain was estimated based on initial and final weights. Feeding deterrence by botanicals was determined compared with the check. Incremental counts showed the powders differed in toxicity. Mesquite and milkweed killed most adults from days 2-6. Neem at 0.05 g was slow acting and killed most adults (two) 14 days after treatment. More weevils were killed before 18 days after exposure to the three doses of botanicals than the check. Botanicals at 0.2 g killed >90% adults, which resulted in least loss of grain (7-16.9%). Percentages of weevils killed by A. indica or A. speciosa did not differ between 0.05- and 0.1-g doses, but loss (18.6-22.9%) of grain was greater than with mesquite. Results will determine botanical extracts to use in formulating biopesticides to control insects in stored sorghum.
Hame Abdou Kadi Kadi*
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