What's eating my crabapple bonsai?

Crabapple bonsai (Malus halliana) is attacked by a range of pests common to all apple family trees. Woolly aphid builds cottony galls on stems and roots. Codling moth and apple sawfly larvae tunnel through fruit. Winter moth caterpillars devour leaves. Fire blight and apple scab follow in the wake of insect damage and wet conditions.

White woolly masses on stems, branch forks, and pruning wounds; corky galls form under the wool; bark cracks and cankers develop; root colonies cause wilting Physical removal with a brush dipped in methylated spirits; systemic insecticide (thiacloprid) for root infestations; parasitic wasp Aphelinus mali gives good natural control — avoid broad-spectrum sprays

Buds eaten from within at leaf burst; holes in young leaves; frass and silk webbing; heavy spring defoliation in some years Apply sticky grease bands to trunk from October to prevent wingless females climbing; spray with Bt at bud burst; hand-pick caterpillars on bonsai

Ribbon-like scars on fruit surface (early feeding); larvae then tunnel into the core leaving a frass-filled hole; affected fruitlets drop in June Use sticky white traps hung in the canopy at petal fall to monitor and trap adults; spray with pyrethroid at petal fall if adults are caught; remove and destroy all fallen fruitlets

Olive-grey or black scabby patches on leaves and fruit; leaves drop early; fruit is cracked and disfigured — particularly problematic on bonsai in wet summers Apply myclobutanil or trifloxystrobin fungicide from bud break through petal fall; collect and destroy fallen leaves; improve air circulation; choose scab-resistant varieties if replanting