What's eating my olive tree?

The olive fruit fly (Bactrocera oleae) is the single most destructive pest of edible olive trees, capable of ruining up to 80% of a fruit crop by laying eggs inside developing olives. Black scale and the olive moth are secondary but significant threats. UK-grown olives face lower fruit fly pressure but scale remains a year-round concern.

Females lay eggs inside developing olives; larvae tunnel through the pulp causing premature fruit drop and rotten, inedible olives; oil quality also drops sharply Use yellow sticky traps and protein bait traps for monitoring; apply spinosad or kaolin clay barrier sprays; harvest as early as possible to avoid peak fly generations

Dark, domed scales cluster on stems and branches; heavy infestations weaken trees significantly; sooty mould develops on copious honeydew Apply horticultural oil in late spring when crawlers are active; prune to open the canopy; encourage parasitic wasps; repeat oil treatments if reinfestation occurs

Three overlapping generations attack leaves, flowers, and young fruit; flower generation causes poor fruit set; fruit generation causes premature olive drop Apply Bacillus thuringiensis (Bt) sprays during flowering to target leaf and flower generations; pheromone traps help monitor adult moth flight

Stippled, silvery or bronzed upper leaf surface; heavy infestations cause yellowing and premature leaf drop, weakening the tree Improve air circulation by pruning; apply neem oil or insecticidal soap; avoid excessive nitrogen fertilising which encourages soft, susceptible growth