Alfalfa Caterpillar
Colias eurytheme
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Egg. |
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Adult butterfly. |
Late instar larva.
Alfalfa caterpillars are larvae of the sulfur butterfly. They are green worms with a white, longitudinal stripe along each side of their bodies. They attain a length of 1/4 to 1/2 inches, and on close inspection appear to have a velvety skin. They are usually held in check by naturally occurring parasites and diseases. Infestations seldom reach economic levels, but damaging populations may occur in southwest Kansas in late summer, especially in fields that stand five weeks or longer between cuttings. If larvae are abundant, sample 5 spots in a field with a sweep net. The economic threshold is an average of 10 larvae per sweep. Cutting the field within the next few days can also substitute for treatment.
Please refer to the most recent version of the Alfalfa Insect Management Guide for specific control options.
Page last updated 4/21/2024 by J.P. Michaud.