How to Manage Pests
UC Pest Management Guidelines
Scientific Name: Otiorhynchus cribricollis
(Reviewed 11/09, updated 11/09, pesticides updated 9/15, corrected 5/18)
In this Guideline:
Description of the Pest
Adults are dark brown compact weevils up to about 0.5 inch long with longitudinal striations. They are flightless and nocturnal, hiding at the base of fruit or under dirt clods during the day and crawling up the tree at night to feed. Larvae are white, legless grubs that feed on tree roots. Adult emergence often begins in May, and adults are present all summer. There is one generation per year.
Adults feed on foliage, notching out the edge of the leaves, giving them a ragged appearance. Under high population pressure, only the midvein of the leaf will remain. Adult feeding on the bark of young twigs may cause dieback. Mature trees can withstand attack without significant damage; however, feeding before harvest may damage fruit stems. Replanted trees may be severely defoliated and die. No damage has been associated with larval feeding.
To reduce damage on young trees that are infested, apply a 3- to 4-inch band of sticky material on the trunk of young trees to trap crawling adults in May when the first adult feeding is observed. Apply Tanglefoot over a special tape or painted areas of the trunk of young trees to prevent bark damage. Reapply the sticky material when it becomes dirty or loses its effectiveness. Alternatively, some growers have had success with an insecticide treatment applied at night when the insects are exposed, but research has not been done to verify this.
UC IPM Pest Management Guidelines:
Insects and Mites
J. A. Grant, UC Cooperative Extension, San Joaquin County
Acknowledgment for contributions to Insects and Mites:J. Colyn, Mid-Valley Ag. Services
M. Devencenzi, Devencenzi Ag. Pest Mgmt. and Research
P. McKenzie, Mid-Valley Ag. Services