Plum lappet

The plum lappet (Odonestis pruni) is a large moth belonging to the Lasiocampidae family. Its wingspan reaches 45–70 mm, and its wings have a unique shape that makes it look like a withered leaf when at rest.

The larvae, or caterpillars, can grow up to 80 mm in length. They are brownish-grey, perfectly blending in with the bark of trees to hide from potential predators.

A distinctive feature of the caterpillars is the presence of two vivid orange or red transverse stripes located on the second and third thoracic segments of the body.

The body of the caterpillar is covered in fine hairs that can cause skin irritation upon contact, serving as a defense mechanism against birds and other insects.

Adult moths are nocturnal and typically remain motionless on tree trunks during the day, relying on their camouflage to avoid detection by birds.

The plum lappet is a polyphagous pest that primarily infests stone fruit trees, including plums, cherries, apricots, and peaches, causing significant stress to the plants.

While stone fruits are preferred, the larvae also feed on pome fruits such as apples and pears, as well as several wild shrubs like hawthorn and blackthorn.

In cases of severe infestation, caterpillars can completely defoliate an entire tree, leading to a major loss in photosynthetic capacity and overall tree vigor.

This loss of foliage prevents the tree from storing sufficient nutrients for winter, which increases susceptibility to frost damage and secondary diseases.

Heavy feeding not only destroys the current harvest but also prevents the formation of fruiting buds for the following season, affecting long-term productivity.

Adult moths emerge for mating in June and July. During this time, females lay eggs in small clusters on the bark or leaves of host plants.

The caterpillars hatch during the summer months and begin feeding actively. They go through several developmental stages (instars) throughout the late summer and autumn.

The species overwinters as young or medium-sized larvae, hiding in bark crevices, twig forks, or within leaf bundles secured with silk.

In spring, as soon as temperatures rise and buds begin to swell, the larvae resume feeding, targeting the young leaves and shoots of the trees.

Pupation occurs in late spring or early summer inside a dense, dark brown cocoon attached to twigs, completing the annual life cycle of the pest.

The most visible sign of an infestation is the presence of large caterpillars resting on the branches, which become active feeders during the nighttime.

Leaves that have been eaten show jagged edges or may be entirely consumed, leaving only the central midribs of the leaves visible on the branches.

Hard, dark-brown cocoons found attached to branches or tucked into deep crevices in the bark are clear indicators that the moth has completed its cycle.

Large amounts of frass (caterpillar droppings) appearing at the base of the trees during late spring can indicate a high density of larvae in the canopy above.

Observing sudden and extensive thinning of the tree foliage during the growing season is a primary indicator of active pest activity in the orchard.

The most effective initial control method is the manual removal of overwintering caterpillars and cocoons during the dormant season pruning.

Cleaning tree trunks of loose, dead bark removes the primary hiding spots where the larvae seek refuge for the winter and during the day.

Biological control using microbial insecticides, such as Bacillus thuringiensis, is highly effective against larvae and is safe for beneficial insects and humans.

If the population reaches a critical threshold, targeted application of selective insecticides can be used, ensuring they are applied during the active feeding phase.

• Proper canopy thinning to maintain airflow and reduce hiding spots.
• Encouraging natural predators like birds and parasitic wasps in the orchard.
• Using sticky bands on trunks to monitor activity and trap larvae.