Strawberry bud weevil
The strawberry bud weevil (SBW) or "clipper" can be a common pest of strawberries. Bud weevils are rare in the southern three tiers of counties in Minnesota, but can be more common in the rest of the state.
Strawberry bud weevil in strawberry flower.
University of Georgia Plant Pathology Archive, University of Georgia
The SBW is a small (about 1/10 - 1/8 inch long), reddish brown weevil with a long snout equipped with feeding mouth parts.
SBW emerges in the spring when strawberry buds first begin to develop. The adults move from their overwintering sites in fence-rows, wooded areas, and berry fields as temperatures reach 60° F in late April or early May. Bud weevils rarely fly or walk more than 30' while looking for food or places to lay eggs. Once they find strawberries, females chew holes in the buds to lay their eggs. Egg-laying peaks during early bloom.
After that, the females clip off the stems (peduncle) which often fall to the ground. The larvae feed in the flower bud for three weeks. The larvae then pupate either in the bud or in the soil with adults emerging in late June through July. These adults feed on pollen from various flowers for a short time and then seek overwintering sites in late summer. There is one generation per year.
The most important injury is caused by the adult females when they damage flower buds and stems. This damage ultimately reduces the amount fruit that is produced. Damage by SBW in home gardens is usually minor but has the potential to be severe under the right circumstances.
Begin sampling for clipped buds when day time high temperatures reach 60 to 65° F and the blossom buds are just starting to emerge from the crown (unexpanded flower clusters). This will require examination close to the ground. Inspect your strawberries at least twice a week. It is not necessary to check strawberries once the buds are open.
- Remove weeds near strawberries that are a pollen feeding source for newly hatched SBW.
- Practice renovation as mowing and removing foliage after harvest removes overwintering sites for the weevils.
If you find at least one clipped bud for every four to five plants, consider treating your strawberries. Count only the newly clipped green buds and not the older clippings which will be shriveled and dry. If the threshold is exceeded seven days after the first spray, another spray application can be made. Be careful with an application as the primary flowers may be opening and the insecticides used for SBW are toxic to bees. Effective insecticides for treating SBW are permethrin, malathion, and carbaryl. Be sure to read and follow all pesticide label directions.