![]() When applying, rain may help move insecticides into the soil where larvae may be resting, but too much rain will move it too deep to target cutworms. In general, the smallest, least mature larval stages are most susceptible to control using an insecticide. However, the impact of these natural predators on cutworm populations in Pacific Northwest production systems is unclear. Natural predators will feed on cutworms readily, including predaceous ground beetles, birds and rodents. Populations of noctuid moths are generally kept under control by a number of natural enemies that include parasitic wasps (Trichogramma species and braconid wasps), parasitic flies in the family Tachinidae, nematodes and several bacterial and viral pathogens. Tilling exposes and kills overwintering and early spring pupae before planting.Removing border vegetation and plant residues can limit the availability of egg deposition sites and alternate food sources for larvae.Moths are active at night and can be monitored with basic light traps. Hay and grass pastures can tolerate as many as 4-6 larvae per sq ft. There are no established thresholds for winter cutworm in grass seed crops, but recommendations for armyworm management suggest thresholds of 1-2 larvae per sq ft in newly planted fields and 3-4 larvae per sq ft in mature stands. Larvae will often curl into a characteristic C-shape when disturbed. Cutworms are often visible at the soil surface when present, but may burrow under leaf litter or under soil clods to rest during the day. If damage is found, search the soil around the damaged plants to a depth of about 2-3 inches for resting larvae. Within fields, look for low-lying irregular patches of plant damage. Sampling and thresholds Field borders should be checked regularly for the presence of larvae - search vegetation for notching, crown damage, or plants cut through the stem at the soil level. Mature larvae will pupate in the early spring, while less mature larvae will continue feeding into the spring before pupating. Winter cutworm is tolerant to cold temperatures, actively feeding September through March when temperatures are above freezing. They are primarily night feeding, which makes detection difficult during the day. The caterpillars are gregarious, similar to armyworms, feeding and moving across the landscape in large groups. Larvae have a wide plant host range and cause a considerable amount of feeding damage to crops in a short amount of time. Females will lay as many as 2,000 eggs over the reproductive lifespan, on both plant and non-plant surfaces, making detection difficult. The adults are strong fliers, can migrate, and are able to disperse over long distances. Periodic outbreaks have occurred, though the environmental conditions leading up to outbreaks are not well understood. Root feeding has also been observed.īiology and life history Winter cutworm was first detected in Oregon in 2001, and was recently reported in high numbers in 2015, feeding on many crops including grass seed fields, cover crops, grass pastures, lawns, meadows, sod, golf course collars, the approach to putting greens, foliage of vegetables, and weeds. They are difficult to identify because of the close similarities to other Noctuid species in this pupal stage, especially armyworm and other cutworm species.Ībove-ground crop damage occurs when larvae chew/notch leaves, or chew through stems completely at ground level (mowing). The pupae are reddish-brown, about an inch long, and found hidden in cavities under the soil and debris about 2-3 inches. ![]() The light brown head capsule has a black upside-down "Y" with two black, angled lines. White or cream lateral stripes run the length of the body. All larvae are characterized by dark brown/black hash marks along the sides and back, becoming more prominent toward the posterior end of the abdomen. Coloration of larvae progresses with development, changing from greenish-gray to dark brown larvae. Winter cutworms are 0.125 to 2 inches in length depending on developmental stage. Eggs require 2 to 4 weeks to hatch, depending on conditions. They are cream in color initially, but darken to yellow as they develop. When at rest, the hindwing (or underwing) is most distinguishable by its bright yellow to orange color with a dark band along the outer margin.Įggs are ribbed and reticulate, and are laid in flat clusters that may be difficult to find on weed or crop foliage. Pest description and crop damage Adults, commonly called large yellow underwing moths, are large (2 inch wingspan) and polymorphic, though consistently dull gray to dark reddish-brown with black markings on the upper surface of the forewing.
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