Many species of Tortrix moth caterpillars feed on the foliage of fruit trees, but most are not regarded as important pests. Certain species do attack apples, pears, plums and strawberries, feeding on the fruit and causing economic damage where they occur.
Apples are the most susceptible crop as they can be attacked by caterpillars of Fruitlet Mining Tortrix moth (Pammene rhediella), Summer Fruit Tortrix moth (Adoxophyes orana) and Fruit Tree Tortrix moth (Archips podana). The Fruitlet Mining Tortrix moth also attacks plums and the Summer Fruit Tortrix moth will attack pears. Strawberry Tortrix moth (Acleris comariana) is an important pest of strawberries, occurring throughout the main strawberry growing regions of the UK.
Fruitlet Mining Tortrix Moth (Pammene rhediella)
There is one generation each year, overwintering as a cocoon under loose bark. Pupae are formed in the spring and adults emerge in May. Adult moths have a wingspan up to 10mm. They are dark brown with a lighter area at the tip of each forewing. Females lay flat, translucent eggs on the underside of rosette leaves. Egg hatch begins after petal fall.
Emerging caterpillars have a black head on a white body, the head turning brown as the caterpillar matures. Feeding damage is caused only on the fruits. Caterpillars feed on the flesh of the fruit and don’t burrow directly to the core. When damaged fruit is harvested, attacked areas have a rough, corky surface and are misshapen due to reduced growth around the feeding area.
Summer Fruit Tortrix Moth (Adoxophyes orana)
Young caterpillars hibernate in cocoons under a piece of dead leaf or bud scale. They are yellow green in colour and emerge from cocoons between bud burst and green cluster growth stages. The caterpillars burrow in to fruit buds and then blossom trusses, before webbing leaves together on young shoots. Pupae are formed in the webbed leaves.
Light brown adult moths emerge during June and July, the females laying batches of around 100 eggs on leaf surfaces. Each egg batch is yellow green and appears waxy. Further caterpillars develop in July and August, giving rise to a second generation of moths during August and September. Young caterpillars produced from the eggs laid by this generation of adults moult once or twice then hibernate. Fruit damage is caused by large caterpillars feeding through July and August.
Fruit Tree Tortrix moth (Archips podana)
Caterpillars of the Fruit Tree Tortrix moth develop more slowly than those of the Summer Fruit Tortrix moth, but in other respects their life cycles are very similar. The first moths appear around mid-June and are active until mid-August. Eggs, which are very similar in colour to leaves, are laid in large scale-like batches.
Caterpillars are yellow with a black head, becoming grey-green with a brown head as they mature. During this generation moulting takes place once or twice before hibernation. On occasion a partial second generation of moths can appear in September and early October. Caterpillars from both generations will damage fruit.
Strawberry Tortrix Moth (Acleris comariana)
There are normally two generations each year. Overwintering occurs as eggs laid by second generation moths. Eggs are laid on the upper and lower surfaces of leaves. Young caterpillars appear in late April and are present until June, and again from July to September. Newly emerged caterpillars are white with a black head, turning to pale green with a brown head when fully grown. Feeding normally takes place on foliage and infestations need to be large to cause economic damage to fruit.
Adult moths have a wingspan of around 15mm. Their colouring varies but there is a clearly visible dark marking half way between the tip and base of each forewing. The first generation emerges in mid-June and a second generation appears from mid-September to the end of October.
Tracer* (active ingredient spinosad) has full approval for control of Summer Fruit Tortrix moth in apples and pears. Tracer enters target insects primarily through contact and ingestion. Contact occurs by direct application or by insect movement on treated surfaces. Ingestion occurs from feeding on treated surfaces. Following entry, Tracer acts on a unique neuro-receptor site of the insect. Symptoms appear almost immediately and complete mortality occurs within a few hours. Tracer is not systemic but does show translaminar movement.
To avoid variable performance with Tracer, timing of application should be optimised and good coverage of the foliage must be achieved. Optimal timing for post-blossom applications of Tracer for the control of caterpillars is when first egg hatch is predicted, based on threshold counts in pheromone traps being reached or exceeded. It is important when making all applications to apples and pears to use sufficient water volume to achieve effective cover and penetration of the foliage.
Lorsban* WG (active ingredient chlorpyrifos) is approved for the control of Tortrix moths in apples, pears, plums and strawberries. Timing of application varies with crop. Repeat applications may be necessary where further generations re-infest crops. Do not apply to crops in flower or to those in which bees are actively foraging. Do not make applications when flowering weeds are present.
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