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Alfalfa Weevil
Larvae
Historically, alfalfa weevil larvae are not a wide spread concern in North Dakota. The light green larvae have a white stripe down the center of the back. They feed in the terminal buds of the growing alfalfa. They may be found in rolled up leaves at the growing tip of the plant. Feeding injury appears as small, circular holes in leaves. As larvae increase in size, feeding injury is more evident. Severely damaged fields take on a silvery appearance due to browning of injured leaf tissue.
Alfalfa Weevil Management:
If alfalfa weevil infestations are observed, one of the best strategies is to cut fields for hay early. After cutting, monitor carefully for signs of damage or delayed re-growth, particularly in the swath area where larvae may be concentrated. When early cutting of the crop is not possible, treatment should be considered when 30% of the plants show feeding damage and larvae are still present. To sample, inspect 20 stems from each of 5 sites in the field, recording the percent damaged plants and whether larvae were found.
See the web site
http://www.ext.nodak.edu/extpubs/plantsci/pests/e1143w15.htm
for insecticide information.
NOTE: When spraying legume fields, apply insecticides between 8:00 p.m. and 8:00 a.m. to protect the local bee population. Never spray fields in bloom.
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