Black vine weevil (Otiorhynchus sulcatus) and raucus root weevil (O. raucus) spend the winter in the soil as pale, legless larvae feeding on the roots of a wide range of plants. It is not known if they feed on the roots of grapevines to any extent.
Although localized and usually confined to the edges of vineyards, infestations of raucus root weevil have occurred occasionally in large numbers that required control. The raucus root weevil was reported from the Okanagan Valley for the first time in 1979, and there have been several localized outbreaks documented since that time.
The flightless adults of both species have long, broad snouts typical of weevils. The thick, roughened front wings are fused together.
Adults range in size from 5.5-7.5 mm for the raucus root weevil and 7.5-10 mm for the black vine weevil. In addition to their slightly smaller size, raucus root weevil can be differentiated from black vine weevil by their generally lighter, patchy appearance and often distinct difference in colour between the head/thorax and the elytra that cover the abdomen.
Black vine weevil adults are a uniform black colour.
Adult black vine weevils feed during late spring and summer on grape clusters and leaves, and sometimes girdle fruit clusters. They are active only at night and remain hidden under plant debris or loose bark during the day, making detection difficult.
Unlike adult raucus root weevil that damage buds, leaves with deeply notched edges not associated with damage from other chewing pests are an indicator of black vine weevil feeding.
Raucus root weevil adults can often be found feeding on the buds of grapes at twilight or on overcast days. Earlier emergence in spring of adult raucus root weevil coinciding with the development of grape buds accounts for the greater damage by this species as compared with the black vine weevil.
Damage by these pests has increased as of late.
Traps for both species can be made from cardboard loosely wrapped around vine trunks where the weevils will hide during the day.
Adults can also be collected on beating trays placed beneath canes and cordons that are hit sharply with a stick. Care needs to be taken, however, as adults often fall to the ground as they are approached.
