How to Manage Pests

UC Pest Management Guidelines

DESCRIPTION OF THE PEST

The olive psyllid can be found in San Diego and Orange Counties. Olive psyllid feeds on olive, Russian olive (Elaeagnus angustifolia) and mock privet (Phillyrea latifolia).

Light green and tan adults are 2.5 mm long and strong jumpers. In olive they don’t move very far, leading to clumped distributions. Forewings are marked with a few small dark spots. Nymphs are flat, green to tan, and secrete a white waxy coating that covers the entire colony. There are five nymphal stages (0.4 mm to 1.5 mm long). The eggs are elliptical, 0.3 mm long, pale yellow, and attach to the substrate by a pedicel.

Depending on temperatures, with 68° to 77°F being optimal, a psyllid can grow from egg to adult in 3 months. There are three generations per year starting in March/April. Females lay one or more eggs on the new shoots, with a single female able to lay 1000 eggs or more. The second generation develops on buds and flowers in May/June. The third generation is often unnoticed, appearing in September/October. Adults overwinter in sheltered areas of the olive trunk.

In warm temperatures (above 80°F), psyllids become inactive. Mortality may occur at temperatures above 90°F.

DAMAGE

Trees that are heavily infested can have yield losses of 30 to 60%. The olive psyllid damages trees through direct feeding on buds, flowers, tender shoots, and small fruit and also through the production of honeydew, which increases sooty mold development. During olive flowering and fruiting, psyllid waxy secretions cause flower and small fruit drop and yield reductions. Large populations may retard the growth of young trees.

MANAGEMENT

Even though the second generation causes the most damage, reduce numbers during the first generation before psyllids secrete their heavy waxy coating, which protects them from pesticides.

Biological Control
Due to its recent introduction, natural enemies feeding on olive psyllid have not been studied, but efforts are underway to identify potential natural enemies in California. Researchers are seeking exotic natural enemies from locations in Europe where the psyllid may be found.

Cultural Control
In areas with hot temperatures, psyllid numbers may be reduced by pruning out center limbs to enhance air circulation.

Monitoring and Treatment Decisions
Olive trees can tolerate low numbers of psyllids without economic damage. You can monitor from March
through May. If psyllid numbers are:

• Below 6 per flower cluster – no loss occurs
• Exceed 6 to 8 per flower cluster in low production years with low set – some loss may occur
• Less than 10 per flower cluster in heavy set years – no to little loss occurs
• Exceeds 10 per flower cluster – loss may occur

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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