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Strawberry
Clipper
Anthonomus
signatus
Biology
The strawberry clipper, Anthonomus signatus, also known as the
strawberry weevil, is a dark, reddish-brown weevil about 1/10 inch long;
its head is prolonged to form a slender, curved snout about 1/3 as long
as the body. Adults overwinter primarily in fence rows and wood lots (although
a small portion of a population may remain in the strawberry field), then
move to plants with developing fruit buds. The seasonal timing of strawberry
flowering coincides with clipper movement from overwintering sites, so
strawberries are ideal host plants for this insect.
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Strawberry
clipper (aka strawberry weevil) Adult is 1/10 inch (2.5 mm) long.
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Damage
Adult clippers first feed on immature pollen by puncturing nearly mature
blossom buds with their snouts. The female then deposits a single egg
inside the bud and girdles the bud, preventing it from opening and exposing
the developing larva. The adult female then clips the stem so that the
bud hangs down or falls to the ground. Larvae feed within the damaged
bud for a period of 3 to 4 weeks; a new generation of adults emerges in
late June and July. These weevils feed on the pollen of various flowers
for a short time, but seek shelter in midsummer in preparation for overwintering.
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An
illustration of the damage caused by strawberry clippers early in
the season
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Control
Because the strawberry clipper does not disperse over long distances,
locating strawberry plantings away from wood lots and hedge rows that
harbor this insect through the winter reduces the number of adults that
move into strawberries in the spring. Because earliest varieties are usually
damaged more than later ones, planting 2 or 3 rows of an early variety
as a trap crop around the perimeter of each field has been suggested as
a way to reduce overall damage or to "concentrate" adults for
control by use of an insecticide.
Integrated
pest management guidelines for strawberries in Massachusetts (Cooley &
Schloemann 1994) recommend sampling for strawberry clipper adults and
damage as soon as flower trusses are visible in crowns. Look for clipped
buds and adult weevils in unexpanded flower clusters. (This should be
a close-up inspection -- hands-and-knees type of work.) Sampling should
be most intensive along field edges near woods or hedge rows. One clipped
bud per 2 ft. of row is enough to warrant an insecticide application for
clipper control; limiting insecticide application to border rows may be
adequate in many instances. If control is necessary, insecticides should
be applied as soon as damage begins to occur, usually well before most
flowers have begun to open. Check the most up-to-date edition of the Illinois
Commercial Small Fruit and Grape Spray Guide for a listing of insecticides
registered for clipper control.
References
Cited
- Cooley, D.R., & S.G. Schloemann. 1994. "Integrated Pest
Management for Strawberries in the Northeastern United States."
Cooperative Extension Service, University of Massachusetts, Amherst.
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