How to Manage Pests

UC Pest Management Guidelines

Olive

Weevils

Scientific Name:
Cribrate weevil: Otiorhynchus cribricollis
Black vine weevil: O. sulcatus

(Reviewed 3/14, updated 3/14)

In this Guideline:


DESCRIPTION OF THE PEST

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.

Damage

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.

Management

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

  1. Prune lower limbs to ensure they do not touch the soil, stopping weevils from climbing into the trees.
  2. Wrap the trunk tightly with plastic wrap or duct tape so that the weevils can not crawl beneath the wrap.
  3. Then apply a 3- to 4-inch band of sticky material such as Tanglefoot or Stikem Special to trap crawling adults when the first adult feeding is observed (typically in May). Apply the sticky material to the plastic wrap, not the tree, because it can soften bark.
  4. Reapply the sticky material when it becomes dirty or loses its effectiveness.
  5. Remove the bands before winter.

Young or newly grafted trees may also be sprayed with carbaryl (Sevin) to help control leaf damage.

Common name Amount to use** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
 
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. CARBARYL*
  (Sevin SL) 5.0–7.5 qt 12 14
  (Sevin XLR Plus) 2 qt 72 14
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: Do not exceed 15 qt carbaryl SL/acre per crop or 15 qt carbaryl XLR Plus/acre per crop per year. To protect bees, apply only during late evening, night, or early morning when bees are not present.
 
** Amounts per 100 gal water (except where otherwise stated), using 400 to 500 gal solution per acre.
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the R.E.I. exceeds the P.H.I. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
1 Rotate chemicals with a different mode-of-action Group number, and do not use products with the same mode-of-action Group number more than twice per season to help prevent the development o resistance. For example, the organophosphates have a Group number of 1B; chemicals with a 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode-of-action group numbers are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Olive
UC ANR Publication 3452

Insects and Mites

F. G. Zalom, Entomology, UC Davis
P. M. Vossen, UC Cooperative Extension, Sonoma County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
M. W. Johnson, Kearney Agricultural Center, Parlier
Acknowledgment for contributions to Insects and Mites:
G. S. Sibbett, UC Cooperative Extension, Tulare County
L. Ferguson, Pomology, UC Davis

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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