Olive Tree Pests: Olive Fruit Fly, Scale, Moth and More

Most garden olives are troubled by only two pests: black scale, which covers twigs with bumps and sticky honeydew, and the olive fruit fly, whose larvae tunnel inside ripening olives. In groves, the olive moth and, locally, psyllids and thrips are added. Good airflow, moderate feeding and regular checks prevent most outbreaks.

Olive Fruit Fly (Bactrocera oleae)

Damage: small puncture marks on the fruit, then brown tunnels and rotting flesh; infested olives drop early and give poor, acidic oil. It is the most damaging olive pest wherever olives are grown commercially, from the Mediterranean to California.

Control:

• Monitor with yellow sticky traps or McPhail-type traps baited with ammonium from early summer.
• Kaolin clay sprays form a white film that deters egg laying.
• Bait sprays (protein bait with an approved insecticide such as spinosad) applied to part of the canopy.
• Mass trapping in small groves.
• Harvest early and pick up fallen fruit to break the cycle.

Black Scale (Saissetia oleae) and Other Scales

Damage: brown or black domed bumps on twigs and leaf undersides, sticky honeydew and black sooty mould; heavy infestations weaken the tree.

Control: prune to open the crown (scale thrives in dense shade), wipe or scrub small infestations off, spray horticultural oil when young crawlers are active (usually early summer), and control ants that protect scale. Natural enemies such as parasitic wasps often keep it in check if broad-spectrum sprays are avoided.

Olive Moth (Prays oleae)

A small grey moth with three generations a year: on leaves, on flowers and in the fruit, where larvae bore into the stone and cause fruit drop in late summer. Bacillus thuringiensis sprays at flowering are the main organic control.

Other Pests

• Olive psyllid: white, cottony wax on flower clusters in spring; usually minor.
• Thrips: scarred, deformed young fruit and leaves.
• Olive bud mite and leaf-curling mites: distorted leaves and buds; more of a problem in nurseries.
• Bark beetles: attack stressed or frost-damaged wood; remove and burn infested branches.
• Indoors: spider mites and mealybugs on potted olives in warm, dry rooms; increase humidity and use insecticidal soap.

Prevention

• Keep the crown open by pruning.
• Avoid excess nitrogen, which feeds scale and psyllids.
• Do not spray broad-spectrum insecticides unnecessarily; they kill natural enemies.
• Harvest on time and clean up fallen fruit.

More Olive Tree Guides

• How to Grow Olive Trees: The Complete Guide
• Olive tree diseases
• Why an olive tree isn't fruiting
• When to harvest and cure olives

Frequently Asked Questions

What are the black bumps on my olive tree?

Almost always black scale insects; look for sticky honeydew and sooty mould nearby.

How do I know if my olives have fruit fly?

Look for tiny sting marks, then soft brown patches and tunnels inside the fruit.

When should I spray for olive fruit fly?

From when trap catches rise and fruit becomes receptive, usually from early summer until harvest; follow local advisory bulletins.

What is the white fluff on olive flowers?

Usually the olive psyllid; it is rarely serious.