Northwest berry Foundation

Management Detail

Weevil, Black Vine Root

in Blackberries

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Latin name: Otiorhynchus sulcatus

Description:

Reason for Concern:
1) Predominant caneberry weevil species. Contributes to serious economic loss.
2) Adults which emerge in early May and June, can contaminate machine-harvested fruit.
3) Grubs weaken canes, devour small rootlets, and destroy the bark and cortex of large roots.

Identification/Symptoms:
Larvae are white or pink, legless, "C"- shaped grubs, about 9 mm long fully grown with distinct brown heads. Found in soil during most of winter and summer. Adults are flightless, hard-shelled beetles, oblong oval, about ½” long, with a broad snout, long, downward curved mouthparts and elbowed antennae. Body is slate gray to blackish-brown and wing covers have many small pits and hairs. They feed at night on foliage and remove large scallops from leaves. Such leaf damage is a good indication that weevils are present but is not economically damaging to the plants. During the day, they hide around the crowns of plants.

Life Cycle:
Adults (nearly all females) appear after bloom, beginning in May, continuing until after harvest season laying their eggs around the crowns about 1 month after emergence. They can lay up to 200 eggs during their adult lifetime (90-100 days). Eggs hatch in 2 to 3 weeks and larvae burrow into the soil to feed on roots and crowns. In the larval stage, size is the only characteristic that distinguishes one species from another. Larvae grow slowly over summer, molting 5 to 6 times. By late fall, they have matured and are about 5/8” long. They enter a prepupal stage in an earthen cell and pupate the following spring/summer. There is one generation per year. Adults are flightless but very active walkers.

Links:

Scouting:

  • In early-mid April, begin taking 10 beating tray samples from several sites in the field (monitoring technique developed by Washington State University, Whatcom County Raspberry IPM Manual), and record the number found. This is most effective at night or on cool cloudy days as this is when weevils will stay in the foliage.
  • In late May, begin examining foliage for weevil feeding signs (notching of the leaf margins).
  • 1 or 2 weevils found for every 10 beating tray samples taken may warrant the consideration of a pre-harvest spray to target those weevils.

 
Cultural Controls:

None listed at present.

 

For information about chemical controls, check with our Pesticide Guide.

images


photo by J. Troubridge


photo by K. Gray


Black vine weevil larvae in roots - W. MacDiarmid


Black vine weevil eggs - K. Gray


Various stages of black vine weevil from larva to pupa, to newly emerged adult with still soft body, to fully black adult - photo by T. Peerbolt

 

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Northwest Berry Foundation

Northwest Berry Foundation

© 2016

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