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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Systematic Entomology Laboratory » Research » Publications at this Location » Publication #423935
Research Project: Systematics of Beetles, Flies, Moths and Wasps with an Emphasis on Agricultural Pests, Invasive Species, Biological Control Agents, and Food Security

Location: Systematic Entomology Laboratory

Title: Injury to soybean seedlings from alfalfa weevil (Coleoptera Curculionidae) larvae

Author
item KOCH, ROBERT - University Of Minnesota
item Chamorro, Maria

Submitted to: Great Lakes Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2025
Publication Date: 9/19/2025
Citation: Koch, R.L., Chamorro, M.L. 2025. Injury to soybean seedlings from alfalfa weevil (Coleoptera Curculionidae) larvae. Great Lakes Entomologist. 58(1):76-78. https://doi.org/10.22543/0090-0222.2503.
DOI: https://doi.org/10.22543/0090-0222.2503

Interpretive Summary: The Alfalfa weevil is a non-native pest of alfalfa in the United States and Canada. These insects are the primarily leaf feeders of alfalfa and the most important insect pest of alfalfa in the Midwest. Feeding by all life stages of this weevil can reduce yield and quality of alfalfa causing major economic losses. While alfalfa weevils primarily feed on alfalfa, they have been reported to feed on other plants. Adult alfalfa weevils have been reported to feed on crops such as soybean if these crops are planted near alfalfa, however, the larva has not been reported to complete its development on soybean. Here we report the first instance of larval alfalfa weevils feeding on soybean seedlings. This situation can potentially occur when soybean is planted into a field containing live alfalfa plants infested with alfalfa weevil. Farmers, extensionists, researchers, and regulators will use this knowledge to reduce crop losses to alfalfa weevils.

Technical Abstract: Alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera Curculionidae), is primarily a pest of alfalfa, but it has been reported feeding on other plant species including soybean. The relatively limited literature on H. postica in soybean indicates that adults and larvae can feed on soybean, but that soybean is not suitable for larval development and survival. There have been instances of H. postica adults moving from alfalfa to nearby soybean fields where they have inflicted significant injury to the soybean plants. Here we report an instance of H. postica larvae causing severe feeding injury to soybean. This infestation of soybean was the result of a “green bridge” created by planting soybean into a field containing live alfalfa plants that were infested with H. postica larvae. After termination of the alfalfa in that field, the H. postica larvae moved to and fed on the soybean seedlings. The observations reported here provide evidence that H. postica larvae can become pests of soybean intercropped (or relay planted) into alfalfa.