Q How do I recognise tortrix moths?
A Tortrix moths attack both fruit plants and ornamental plants. They are nocturnal, whereas fruitlet-mining moths are active by day – they are dark brown with a 10mm wingspan and a pale, metallic wingtip. The caterpillars are thin and up to 25mm long. Fruitlet-mining moth caterpillars are grey/green, summer fruit tortrix light green and fruit-tree tortrix whitish. Look out for them wriggling backwards when touched. The caterpillars feed on leaves, often spinning shelters of leaves or rolling them into protective tubes. They then move on to fruit, usually hiding by attaching a leaf to the fruit with silk and feeding beneath it. The damage is only to the fruit surface.
Caption: Open up rolled leaves and you may find tortrix-moth caterpillars hiding inside
Q Can you tell me more about them?
A Fruitlet-mining moth caterpillars overwinter in a cocoon beneath the bark and pupate in spring. The females emerge in May and lay eggs under rosettes of leaves. After petal-fall they hatch and grow to full size by late summer. Summer tortrix-moth caterpillars overwinter in a cocoon beneath a bud scale or dead leaf, and start feeding again in the spring, initially on young fruit buds, blossom, and then the leaves. They pupate in mid-summer. The emerging moths lay eggs on leaves, which hatch into caterpillars and feed in late summer – these cause the most damage. Fruit-tree tortrix caterpillars overwinter in a cocoon under bark and pupate in mid-summer. They lay eggs in green blobs beneath leaves. Some early developers pupate in spring, giving rise to a second generation of caterpillars in early autumn. Both generations can damage fruit.
Q What damage do they cause?
A The feeding of all tortrix moths produces shallow depressions with dark margins in the fruit. Some bore deeper, but seldom as far as the core. By harvest, the wounds will have healed, leaving a corky or russeted covering, distorting growth around the damage. They are a problem in mid- to late summer. Fruitlet-mining tortrix makes a shelter of webbing in clusters of apples. Summer fruit tortrix shelter in leaves held together by silken webbing near the tips of shoots. Fruit-tree tortrix caterpillars hide beneath silken shelters of leaves and fruit or in the eye of the apple, and can be hard to spot.
Q Can I spray against tortrix moths?
A Yes, if your trees are small. Treat with an insecticide approved for caterpillar control on fruit following the information on the packet for which trees they can be used on and how often you need to spray.
Q Are there any organic options?
A There are pheromone traps available – if more than 30 moths a week are caught, be ready to spray 10-14 days later.
Q Can I leave it to nature to take care of them?
A Usually, yes. There are many predators of these insects.