Phil Mulder, Oklahoma State University
Typically considered to be a secondary pest of grapes in most growing regions, climbing cutworm is a catch-all category for a number of larvae in the Noctuidae family. A caterpillar about 1 1/4 to 1 3/4 inches long, the head is dark and the body is dull gray-brown with spots or stripes.
Buds and shoots may be injured or destroyed by feeding of larval stages of up to 10 different species of cutworms. In the spring, cutworms feed at night and rest during the day, concealing themselves either under loose bark on the trunk or beneath the grape trellis. Vineyards with vegetation under the row provide an ideal habitat for climbing cutworm. You will only see larvae feeding on vines if you scout at night. They crawl up the grape trunk on warm spring nights and feed on green tissue from bud swell to 5-inch shoot growth.
As this is a sporadic pest of grapes, yearly scouting is critical to catch populations before they get out of hand. Inspect buds starting at bud swell. In years where shoot growth is hampered by cool conditions, repeated scouting until shoots reach the 5-inch growth stage may be required. If damage has occurred in the vineyard in the past, check those areas of the vineyard first. Inspect 100 vines and record the number of damaged buds/shoots. Apply insecticide in areas where more than 4 percent of the new buds are damaged. This threshold can be adjusted according to the variety grown, number of buds retained, and training system.
Larvae overwinter in soil, becoming active when buds begin to swell, especially after warm nights. Vines are no longer at risk after about the 5-inch shoot growth stage. Cutworms are considered to be a sporadic pest and are typically only a problem in years where weather conditions keep the buds/shoots in a susceptible stage. Damage is generally more common in lighter, sandy soils where vegetation (weeds or cover crops) are growing under vines. Keeping a vegetation-free strip under the row can significantly reduce the amount of climbing cutworm damage in grapes.
Cutworms, University of New Hampshire
Field Guide for Integrated Pest Management in Pacific Northwest Vineyards, Washington State University
Reviewed by Eric Stafne, Mississippi State University and Tim Weigle, Cornell University