Black Vine Weevil
(Otiorhynchus sulcatus)
Insects and Invertebrates
Adults are up to 1/3 inch long, black with a few small yellow or orange spots.
Symptoms
There are a number of species of weevils found in caneberry fields. The Black Vine Weevil is the most predominant species and contributes to serious economic losses. Larvae feed on roots and can completely devour small rootlets and destroy the bark and cortex of larger roots. Plants will soon begin to wilt because they are no longer able to provide moisture for the leaves. Adults feed on foliage, removing large scallops (notching) from the leaves. This notching is a good indication weevils are present but is not economically damaging. Adults can be a contaminate in machine-harvested fruit.
Identification
Larvae are white or pink, legless, C-shaped grubs. They are about 1/3 inch long when fully grown and have distinct brown heads. They can be found in the soil during most of the winter and summer. Adults are flightless, hard-shelled beetles. They are oblong oval in shape, about ½-inch long. They have a broad snout, long downward curved mouthparts and elbowed antennae. The body is slate gray to blackish-brown and the wing covers have numerous small pits and small hairs. They feed at night in the canopy and hide around the crown of plants during the day.
Life History
The adults, nearly all female, appear after bloom, beginning in May and continuing throughout the harvest season. They feed on foliage within the plant canopy at night and are found during the day hiding around the crown of the plant. Weevils may stay in the foliage on cool, cloudy days especially if the foliage is dense. They lay several eggs each day around the crown, resulting in around 200 eggs during their adult lifetime (90-100 days). Eggs hatch in two to three weeks into young larvae that work their way into the soil and feed on roots and crowns. Larvae grow slowly over the summer, molting five to six times. By late fall they have matured and are about 5/8 inch long. They enter a quiescent pre-pupae stage in an earthen cell and pupate the following spring/summer. There is one generation per year. Because they are flightless, migration can be relatively slow; however, they are very active walkers.
Monitoring
In early spring, inspect roots of plants with low vigor for larva. Plants damaged by larvae may show symptoms similar to water stress. In late May, begin inspecting canes for signs of damage, which appears as notching of leaf margins. Temporary shelters, such as a roof shingle, can be used to detect adults seeking shelter during the day. Developmental stage should be noted to help time effective treatments.
Adult weevils can be detected in the evening by placing a beating tray under the foliage and shaking the plant gently. Take 10 beating tray samples (spaced 3-5 hills apart) at each of 3-5 sites per field and record the total number of adults found. If a beating tray is not available, placing a white sheet on the ground and shaking the canopy above can also work. Record weevil numbers for each inspection. Resample soon after treatment.
Thresholds and Management
Fields can rapidly become infested in a short time, therefore controls should be applied to even lightly infested fields to prevent an increase in infestation. A pre-harvest spray is advisable if beating tray sampling results in 1-2 weevils per ten samples. Scout field soon after treatment to verify effectiveness.
Adult weevils are nocturnal feeders and become active after sundown. Applying foliar sprays at night will usually improve efficacy of the insecticide by escalating the chance weevils are directly hit by the spray or increasing the likelihood they will walk through a fresh spray deposit.
Resources
Ohio State University, Extension Fact Sheet: Black Vine Weevil,
http://ohioline.osu.edu/hyg-fact/2000/2016.htmlUniversity of California, IPM Online: Caneberries, Root Weevils,
http://www.ipm.ucdavis.edu/PMG/r71300411.htmlWSU Extension, Bulletin 0965, Root Weevils on Berry Crops
http://cru.cahe.wsu.edu/CEPublications/eb0965/eb0965.htmlWSU Extension, Western Washington Field Guide to Common Small Fruit Root Weevils
http://cru.cahe.wsu.edu/CEPublications/eb1990/eb1990.pdf
Secondary content using h2 tag.
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
Heading using the h3 tag
Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.