How to Manage Pests
UC Pest Management Guidelines
Cribate weevil adults are dark brown with longitudinal striations. The black vine weevil adult is black with small patches of white scales. Both are about 0.5 inches (12.7 mm) long. They are flightless and nocturnal. The adults, nearly all females, emerge in late spring or early summer. Larvae are white, legless grubs, with distinct brown heads that feed on tree roots. Root weevils overwinter as larvae. There is one generation per year.
Adults feed on foliage and scallop leaf edges. Leaf damage is a good indication that weevils are present but is not damaging to established trees. Adult feeding may cause economic damage to young or newly grafted trees. Root feeding of larvae has not been associated with damage to olives.
No management is necessary for this pest in established trees. For young trees, monitor for infestations by checking trees at night with a flashlight. To prevent infestation, prune lower limbs to ensure they do not touch the soil, stopping weevils from climbing into the trees, then apply a 3- to 4-inch band of sticky material such as Tanglefoot or Stikem Special to the young trees to trap crawling adults when the first adult feeding is observed (typically in May). First, wrap the trunk tightly with plastic wrap or duct tape so that the weevils can't crawl beneath the wrap. Apply the sticky material to the plastic wrap, not the tree, because it can soften bark. Reapply the sticky material when it becomes dirty or loses its effectiveness. Remove the bands before winter.
UC IPM Pest Management Guidelines: Olive