Apple Maggot
The larva of Rhagoletis pomonella, a small fly with banded wings. Adults emerge from mid-June onwards and females use a needle-like ovipositor to insert single eggs just under the fruit skin. Larvae are white, legless maggots 6 - 8 mm long that burrow through the flesh in winding tunnels, causing the fruit to rot from inside. Primarily a pest in eastern North America.
Symptoms to Look For
- Tiny puncture marks in the skin where eggs were inserted, sometimes with a slight dimple
- Winding brown streaks or corky tunnels through the flesh when the fruit is cut open
- Fruit feels soft in spots and rots prematurely, often while still on the tree
- Early fruit drop from late June through August, fruit apparently healthy on the outside
- Small white maggots found inside rotting fruit, most visible near the core
Affected Plants
Organic Solutions
Red Sphere Sticky Traps
Hang red sticky sphere traps (approximately 7 cm diameter) coated with Tanglefoot or similar adhesive from late June, one trap per dwarf tree, two to four per standard. Flies are attracted to the sphere thinking it is a fruit. Replace or re-coat when the surface is covered. Use traps both to monitor and to reduce adult populations.
Kaolin Clay Spray
Begin applying kaolin clay from late June when adults first emerge and continue every 7 - 10 days through August. Coat all fruit surfaces thoroughly. The particle film deters females from inserting eggs and makes fruit surfaces physically difficult to penetrate. Reapply after rain.
Exclusion Bags on Individual Fruit
After the June drop and once fruit has reached marble size, slip small organza or paper bags over individual fruits and secure. This physically prevents flies from reaching the fruit surface entirely. Effective for hobbyist growers with manageable crop sizes.
Remove Host Plants Nearby
Wild crabapples and hawthorns within 100 m are significant reservoirs of apple maggot fly. If possible, remove them or harvest fruit promptly to prevent adjacent populations building up and migrating to cultivated trees.
Prevention
- Hang red sphere monitoring traps from mid-June every year - population data makes interventions far more precise than calendar timing
- Remove all fallen fruit within 2 - 3 days throughout the season - maggots in fallen fruit continue to develop and pupate in the soil beneath the tree
- Apply kaolin clay from late June as a season-long barrier - early, consistent coverage before peak egg-laying is significantly more effective than late intervention
- Check and bag individual fruit after June drop if the crop is small enough to manage - physical exclusion is close to 100% effective
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.