How to Manage Pests

UC Pest Management Guidelines

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. Chemical treatment is rarely needed for olive scale unless biological control is disrupted by treatments applied for other pests.

Biological Control
Olive scale is effectively controlled by two parasites Aphytis maculicornis and Coccophagoides utilis.

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.+
(trade name)			(hours)	(days)
When choosing a pesticide, consider information relating to the impact on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
POSTBLOOM (Late May through June when crawlers are present)
A.	NARROW RANGE OIL#	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 . . .
	CARBARYL*
	(Sevin) 80S	1–1.25 lb	12	14
	MODE OF ACTION GROUP NUMBER1: 1A
	COMMENTS: Do not exceed 2 applications/year. This material is very destructive to most natural enemies. 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#	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. Do not apply any oil between August 20 and harvest to olives used for Spanish or green-ripe processing because of the risk of fruit spotting. 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. 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) 80S	1–1.25 lb	12	14
	MODE OF ACTION GROUP NUMBER1: 1A
	COMMENTS: Do not exceed 2 applications/year. This material is very destructive to most natural enemies. 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#	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 12 lb/acre/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.
**	Amounts per 100 gal water (except where otherwise stated), using 400-500 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/.

PUBLICATION

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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