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Control of Strawberry Root Weevils | |
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Description and Life History
Adult strawberry root weevils, Brachyrhinus ovatus (L.), are hard-shelled insects about 6 mm long, with short blunt snouts. They are brown to black in color and unable to fly. Both adults and larvae (grubs) overwinter under soil trash and around the base of food plant hosts. Adults come out from their overwintering sites in late spring and early summer and begin migrating in search of food hosts around which to lay eggs. Eggs are also laid in late summer during the second period of weevil migration,
Eggs hatch in 2 to 3 weeks into legless, whitish grubs. The larvae immediately begin feeding on the roots of host plants. Full grown larvae are 12 mm long, slightly curved and have pale brown heads. Larvae that hatch from eggs laid early in the summer are transformed into adults during the fall. Larvae that hatch from eggs laid in late summer overwinter in the soil and develop into adults late the following summer. Adult females die after laying 200 - 300 eggs each.
Adult weevils are usually seen crawling about in early summer and again in late summer to early fall.
Food Hosts and Damage
Adult strawberry root weevils do little noticeable damage except for slight feeding on the leaves of strawberry, clover and some grasses and weeds. Leaf feeding is characterized by small notches along the leave margins. Adults will feed on strawberries, making small holes in the fruit. Most of the economic damage is caused by the larvae feeding on the roots of strawberry, raspberry, various clovers, grasses (especially timothy) and nursery evergreens. Strawberry plants may be seriously damaged when larvae are abundant. Affected plants will appear stunted and the leaves will be closely bunched and dark colored or dying. Seedling evergreens are often weakened or killed by larval feeding damage to the roots.
Most complaints about strawberry root weevils occur because of their abundance in early and late summer when they become a nuisance to homeowners. When migrating, the weevils go through houses rather than around them, gaining access through spaces beneath doors, around basement windows and between the house and foundation, When abundant, they can be found crawling on floors, walls, ceilings, in sinks and bathtubs and on bedding and clothing. The adult weevils are not harmful to humans.
Control
Outdoors
If there is a history of weevil damage to strawberry plants in previous years, the insect can be controlled in the spring by applying a spray of malathion 50% EC (5 -10 ml/L water) when fresh leaf notching is noticed. Repeat in 10 days or when more leaf notching occurs.
Indoor
There is no practical or acceptable indoor insecticide from a health or safety standpoint that can be used to stop weevils from entering the home. The best control procedure is to prevent weevils from entering buildings by ensuring there are no cracks or spaces beneath doors, door frames, basement windows, etc. Seal any cracks with caulking compound or other suitable material, and install weather stripping where required.
If weevils do enter the house, use a broom or vacuum cleaner to collect and remove them from the building. The insecticide treatment recommended is an outdoor spray using malathion 50% EC (30 ml/L water) applied to the lawn and ground in a 40 - 50 cm wide strip around the building foundation. The spray may also be applied to the exterior of the foundation. Avoid spraying ornamental plants with malathion insecticide.
Source: Agdex 620-1.
The contents of this page are no longer available.
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For more information about the content of this document, contact Shelley Barkley.
This document is maintained by Ada Serafinchon.
This information published to the web on May 11, 2001.
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