Description of the Pest
Adults of the Pacific Coast wireworm are about 0.5 inch (13 mm) long, reddish brown to black, with a prothorax that has pointed posterior tips. They are commonly known as click beetles because, if held, they will bend their body backwards and then quickly straighten it to create an audible snap.
The larval stage of this insect lives in the soil and is commonly referred to as a wireworm. Wireworms have hard bodies that are slender, cylindrical yellowish to brown in color, and about 0.75 inch long when full grown. It takes about 3 to 4 years for the wireworm or click beetle to complete its life cycle. Most of the time is spent in the larval stage, but all stages may be present at once. In grapes, the larval stage is not considered a pest whereas the adult click beetle can be damaging.
The click beetle can feed on buds in spring. The injury to the bud looks essentially the same as that of the grape bud beetle. Unlike the grape bud beetle and the cutworm, the click beetle is a day feeder. Overwintering in the ground litter, it emerges in spring on warm days. Click beetles are often seen in large numbers resting on cover crops during the day. Even with these high populations in the vineyards, they seldom cause economic damage to grapes.
No material is registered for use on this pest; however, click beetles usually occur in conjunction with cutworm infestations and it has been observed that the spray materials used for cutworms also control click beetles.