Chapter 21

Managing Vineyard Insect and Mite Pests

Climbing Cutworms

The name “cutworm” is applied to a large number of larvae of lepidopterous species in the family Noctuidae. The larvae are called cutworms because they climb vines and feed upon foliage, buds and shoots (See Figure 21.1).

Symptoms

Damage to grapevines occurs from bud swell to when shoots are several inches long. Only during bud swell are cutworms able to inflict serious damage to a vineyard. Injured buds may fail to develop canes or clusters, which can cause significant yield reduction in some varieties. When primary buds are destroyed, secondary buds emerge.

Life Cycle

Cutworms usually overwinter through several stages (instars) as feeding larvae (caterpillars) in the soil, or under debris in the vineyard. When temperatures become warm in early spring, the larvae become active emerging at night to feed on winter annual weeds.

Monitoring

Monitoring for cutworms should begin during bud swell in early spring. Because cutworm infestations are localized, many vines must be examined to detect their presence. Newly planted vines need special protection. Frequently the disturbance of weeds or other cover in the planting process leaves little food for resident cutworms.

Pest Management

Cultural Practices

Removing weed-dominated ground covers during spring is often followed by major damage to grapes because it can cause movement of cutworms to the grapevines.

Applying Control Materials

Timing of spray treatments is very important since cutworm larvae, once they have become active in the spring, can cause serious bud damage in a short time. If bud damage reaches one to two percent, it is justifiable to apply one or more insecticide treatments. As damage tends to recur in the same spots in the vineyards, growers often use the previous year’s infestation as a cue to spot treat these same spots the following year. By using this method and treating early, the pest can often be controlled with a minimal amount of acreage treated. To minimize the impact on beneficial insects spraying is directed at the ground and lower trunk instead of the entire vine canopy.

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