Strawberry Bud Weevil or Strawberry Clipper
The beetles leave their winter quarters in fence rows and woodlots in the spring as temperatures approach 60°F, usually around the end of April. They immediately proceed to a number of plants with early fruit bud developments, of which strawberries are phenologically ideal. First, they feed on immature pollen by puncturing the blossom buds with their long snouts. The female deposits a single egg inside the nearly mature bud and then girdles the bud. She then clips the bud so it hangs by a mere thread or falls to the ground. In about one week, the egg hatches into a white, legless grub. The larva develops inside the bud and reaches maturity in 3 or 4 weeks.
Adult weevils emerge from the buds in June. After feeding on the pollen of various flowers for a short time, the new adults seek hibernating sites in midsummer and remain inactive for the rest of the season. Weevils remain in these sites until the next spring. Only one brood appears each year. Injury is most likely to occur when strawberries are grown adjacent to woodlots or other suitable hibernating quarters.
Clipping begins in early May, and growers should check their field carefully at that time for the first signs of damage. To determine if a pesticide treatment is necessary, walk random rows of plants, keeping track of the number of cut buds per linear foot of row. Sample five separate 10-foot sections from throughout the field. Divide the total number of cut buds observed by the total number of linear row feet inspected. If more than one cut bud per linear row foot is found, a pesticide treatment is justified. Pay particular attention to fields near woods and hedgerows. Treatment of field borders only may be sufficient in some instances. Apply the first spray in early May when there is one cutback per linear foot of row. Apply a second spray 10 days later.
Mulches and full canopy beds can encourage newly emerged adults to remain in the planting, causing damage to occur in succeeding years. Cropping fields less than 3 years, plowing under old beds immediately after harvest, and removing the foliage and mulch to reduce the suitability of overwintering sites help lessen the chances of clipper damage.