Pachypasa truncata

Pachypasa truncata belongs to the Lasiocampidae family, order Lepidoptera. It is a large nocturnal moth with a wingspan of up to 80–100 mm, featuring a characteristic grey-brown coloration with dark transverse bands.

The larvae of this species are substantial in size and covered in dense hair, which can cause skin irritation in humans. The coloration of the larvae varies from grey to brown, providing excellent camouflage against tree bark.

Pupae develop within dense cocoons that the pest attaches to branches or hides within crevices of the bark. Adults exhibit sexual dimorphism, with females generally being larger than males.

The insect's life cycle is closely linked to regional climate conditions. Reproduction occurs sexually, and eggs are laid by females on the surface of leaves or tree bark.

Detecting this pest requires careful inspection of the tree canopy during the spring-summer period, as larvae lead a concealed lifestyle and are primarily active at night.

The primary damage is caused by the larval stage (caterpillars), which possess powerful chewing mouthparts. They actively feed on the foliage of various tree species, leading to defoliation and weakening of the plants.

The range of host crops includes both forest stands and fruit orchards. The pest poses a particular threat to coniferous and deciduous trees, damaging buds and young shoots.

In cases of mass outbreaks, Pachypasa truncata can completely strip a tree's canopy in a short period. This disrupts photosynthesis, reduces wood growth, and increases susceptibility to secondary infections.

In fruit farming, the pest negatively impacts yields, as damage to the leaf apparatus prevents proper fruit ripening. Prolonged caterpillar feeding can lead to branch desiccation or the death of the entire tree.

Damage is characterized by the consumption of leaf blades down to the veins, giving trees a distinct ragged or skeletonized appearance.

Adult moth emergence typically occurs in late summer or early autumn, when mating and egg-laying take place. The insect most often overwinters in the early larval stage, hiding in forest litter or bark crevices.

Active feeding by caterpillars begins in early spring, immediately after sap flow starts and new leaves appear on trees. This period is the most critical for plant protection.

The pupation period occurs in late spring or early summer. After completing metamorphosis, the imago emerges from the pupa, completing the annual development cycle.

Weather factors, such as an early and warm spring, can significantly accelerate larval development. Unfavorable conditions, conversely, may suppress the pest population.

Monitoring the population is recommended using pheromone or light traps, which help determine the start of the moth flight season.

The primary sign of the pest's presence is the occurrence of skeletonized leaves and a noticeable reduction in canopy density. Early detection is difficult due to the larvae's camouflage.

The presence of frass (excrement) on the ground under the tree often indicates the presence of a large caterpillar population in the canopy. The waste appears as characteristic dark granules.

The presence of dense silken nests or cocoons on branches is a direct indicator of pest reproduction. It is necessary to inspect branch forks and leaf attachment points.

A decrease in leaf turgor and premature leaf fall in the absence of drought can also indicate insect damage. The tree appears stressed and weakened.

During mass infestations, a specific noise created by the feeding process of numerous caterpillars can be heard.

Mechanical methods include manual collection of caterpillars and removal of nests, followed by destruction. This method is effective only in small areas or on young trees.

Biological preparations based on Bacillus thuringiensis show high efficacy against larvae of all ages and are safe for beneficial insects and the environment.

Chemical control methods involve spraying systemic or contact insecticides during the period of mass caterpillar emergence.

An important preventive measure is maintaining tree health, timely pruning of dry branches, and fertilization to increase the natural resistance of the plants.

• Attracting natural enemies: insectivorous birds and predatory insects.
• Using sticky bands on trunks to limit the movement of caterpillars.
• Adhering to quarantine measures during the transport of nursery stock.