How to Manage Pests

UC Pest Management Guidelines

Olive

Olive Scale

Scientific Name: Parlatoria oleae

(Reviewed 3/14, updated 3/14)

In this Guideline:


Description of the pest

Olive scale is an armored scale and like all armored scales, resembles a small encrustation on the plant. The adult female scale is about 0.10 (2.5 mm) inch long, with a grayish, oval, waxy covering. The male scale is more elongate with a black spot at one end. If the coverings are removed, the scale bodies of both sexes are reddish purple. Olive scale feeds on twigs, leaves, and fruits. However, it is most often noticed at harvest; dark purple spots occur on otherwise green to yellowish fruit where the scale has settled. There are several generations a year.

Damage

Early in the growing season (late May and June) first brood olive scale feed on and consequently deform young, rapidly growing fruit. A later brood, in July and August, causes the pronounced purple spotting of green fruit, rendering it worthless for most markets except perhaps black ripe process. Heavy olive scale infestations will also occur on branches, twigs, and leaves. Such infestations substantially reduce the productivity of a tree.

Management

Olive scale can be effectively controlled by natural enemies and does not usually cause economic damage. Preserve natural enemies by selecting insecticides for other pests that do not kill beneficial insects. Control ants in the orchard because they disrupt biological control (for more information, see ANTS).

Biological Control

Olive scale is effectively controlled by two parasites Aphytis maculicornis and Coccophagoides utilis. Where insecticides such as carbamates (IRAC Group 1A), organophosphates (1B), and pyrethroids (3) are used, biological control will be disrupted. Be sure to monitor scale populations if disruptive insecticides are used.

Organically Acceptable Methods

Biological control and certain oil sprays are acceptable to use in an organically certified crop.

Monitoring and Treatment Decisions

If olive scale was detected in the previous season or if disruptive chemicals are used in the orchard or on nearby crops, watch closely to detect crawlers moving onto fruit in spring and summer. Double-sided sticky tape can be applied to branches to help detect the presence of crawlers. If treatments are needed, control the first brood in late May and June or the second brood in late July and August. Apply first brood treatment when scale crawlers are seen moving on to the fruit. Treating scales in early July, between broods, is not recommended. A postharvest treatment is also effective. One of these treatments is usually all that is needed.

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.
 
POSTBLOOM (LATE MAY THROUGH JUNE WHEN CRAWLERS ARE PRESENT)
 
A. NARROW RANGE OIL#
  (Organic JMS Stylet Oil, etc.) Label rates 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Effective against light to moderate infestations, especially when used in conjunction with pruning to open the orchard canopy. Most effective when applied against the crawler stage. Spray at night or early morning if temperatures are expected to exceed 90°F during the day. Check with certifier to determine which products are organically acceptable.
 
B. PYRIPROXYFEN
  (Esteem 0.86EC) 13–16 fl oz 12 7
  MODE-OF-ACTION GROUP NUMBER1: 7C
  COMMENTS: Insect growth regulator. Has no activity on adult stage, but hatching of eggs laid by treated adults will be suppressed. Most effective when applied against the crawler stage. Use higher rate for high scale numbers.
 
C. NARROW RANGE OIL 1.5 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: For heavy to severe infestations, add the following insecticide to the oil spray. Spray at night or early morning if temperatures are expected to exceed 90°F during the day.
  . . . plus . . .
  CARBARYL*
  (Sevin SL) 5.0–7.5 qt 12 14
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: Do not exceed 2 applications per year. This material is very destructive to most natural enemies. To protect bees, apply only during late evening, night, or early morning when bees are not present. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
SUMMER (JULY 15–AUGUST)
 
A. NARROW RANGE OIL#
  (Organic JMS Stylet Oil, etc.) Label rates 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Effective against light to moderate infestations, especially when used in conjunction with pruning to open the orchard canopy. Most effective when applied against the crawler stage. Spray at night or early morning if temperatures are expected to exceed 90°F during the day. Check with certifier to determine which products are organically acceptable.
 
B. PYRIPROXYFEN
  (Esteem 0.86EC) 13–16 fl oz 12 7
  MODE-OF-ACTION GROUP NUMBER1: 7C
  COMMENTS: Insect growth regulator. Has no activity on adult stage, but hatching of eggs laid by treated adults will be suppressed. Most effective when applied against the crawler stage. Use higher rate for high scale numbers.
 
C. NARROW RANGE OIL 1.5 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: For heavy to severe infestations, add the following insecticide to the oil spray. Do not apply any oil between August 20 and harvest to olives used for Spanish or green-ripe processing due to fruit spotting. Spray at night or early morning if temperatures are expected to exceed 90°F during the day.
  . . . plus . . .
  CARBARYL*
  (Sevin SL) 5.0–7.5 qt 12 14
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: Do not exceed 2 applications per year. This material is very destructive to most natural enemies. To protect bees, apply only during late evening, night, or early morning when bees are not present. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
POSTHARVEST (OCTOBER–NOVEMBER)
 
A. NARROW RANGE OIL#
  (Organic JMS Stylet Oil, etc.) Label rates 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Effective against light to moderate infestations, especially when used in conjunction with pruning to open the orchard canopy. Most effective when applied against the crawler stage. Spray at night or early morning if temperatures are expected to exceed 90°F during the day. Check with certifier to determine which products are organically acceptable.
 
B. NARROW RANGE OIL 1.5 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: For heavy to severe infestations, add the following insecticide to the oil spray. Spray at night or early morning if temperatures are expected to exceed 90°F during the day.
  . . . plus . . .
  METHIDATHION*
  (Supracide 25WP) 2 lb 48 0
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: Use with or without oil. Application of methidathion with, or closely following, a fungicide containing lime will negate the insecticide's effectiveness. The application of this material should precede the application of fungicides containing lime. Do not apply more than than 12 lb/acre per year. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i. 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 REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* Permit required from county agricultural commissioner for purchase or use.
# Acceptable for use on organically grown crops.
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 of 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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