Clover Leaf Weevil in Alfalfa
Crop Injury: Clover leaf weevil (Hypera zoilus) has been present in the U.S. for more than 140 years. Adults and larvae consume alfalfa foliage starting in the lower plant canopy and moving upwards. Leaves with feeding injury appear ragged and severe plant defoliation can occur with high weevil populations. Clover leaf weevil prefers to feed during the night or under cloud cover, retreating to the alfalfa plant base when it is sunny.
Pest Description: Adult weevils are dark brown and speckled with lighter- and darker-colored scales. Adults have a faint stripe on each wing cover and are 5/8 inch in length. Legless larvae have a brown head, are yellow to green with a single white stripe with pinkish borders along the back.
Clover leaf weevil
Whitney Cranshaw, Colorado State University, Bugwood.org
Clover leaf weevil
Whitney Cranshaw, Colorado State University, Bugwood.org
Life Cycle: Overwintering occurs most commonly as larvae or eggs. Larvae become active in late winter to late spring and feed on plants. Cocoons are formed on or near plants, protecting the insect during pupation. Emerging adults consume alfalfa tissue and then become inactive until fall egg laying. Clover leaf weevils have one generation per year.
Scouting: Clover leaf weevil can be confused with alfalfa weevil. Check fields right after the first cutting, especially when weather conditions have been dry.
Management: A fungal pathogen which thrives in warm and wet conditions typically keeps clover leaf weevil populations low. Be aware that weevils may flourish during cool and dry springs, when fungal development is limited. Insecticide application can control clover leaf weevils.
Prepared and reviewed by the Alfalfa Pest Management Working Group.
Clover leaf weevil. Whitney Cranshaw, Colorado State University, Bugwood.org
Clover leaf weevil. Whitney Cranshaw, Colorado State University, Bugwood.org
Gallery images courtesy Whitney Cranshaw, Colorado State University, Bugwood.org.
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