White-spotted wood borer

The White-spotted wood borer (Zeuzera leuconotum) is a member of the Cossidae family, a group of moths known for their wood-boring larvae. Adult moths are easily recognized by their white wings decorated with numerous dark spots and a distinct white, fuzzy thorax.

These moths have a wingspan reaching 60–70 mm. They exhibit sexual dimorphism, with females being notably larger than males, which is a common trait among many species of the leopard moth group.

The larvae are cream-colored with a dark head and numerous small plates along their body. They spend almost their entire life cycle hidden deep within the woody tissue of host trees.

As a species within the Lepidoptera order, its life cycle is highly specialized for feeding on perennial woody plants, requiring precise timing for any effective control measures.

The adults are relatively short-lived and do not feed, focusing entirely on mating and egg-laying to ensure the survival of the next generation.

This pest is a significant threat to various broadleaf tree species. It frequently attacks fruit trees like apples, pears, and plums, as well as several ornamental and forest trees including willows and poplars.

The primary damage is caused by the larvae, which bore intricate tunnels through the wood. This activity compromises the structural integrity of the branches and disrupts the plant's vascular system.

Affected trees often show signs of stunted growth, leaf yellowing, and decreased fruit production due to the inability of the tree to transport nutrients and water effectively.

In severe infestations, the galleries created by the larvae weaken the trunk or large limbs, making the tree susceptible to wind breakage and secondary fungal infections.

Young trees are particularly vulnerable; a single heavy infestation can lead to the death of the entire plant by girdling the main stem or causing extensive internal tissue destruction.

The flight period for the adults typically occurs from late spring through the summer months, depending on the specific regional climate and temperature patterns.

After mating, females lay eggs near buds or in cracks in the bark. Once hatched, the young larvae immediately begin to burrow into the tender tissues of the branches.

The larval stage is long, often lasting up to two years, meaning that the pest remains active inside the tree throughout multiple seasons, including overwintering within the wood.

Pupation takes place within the larval galleries. As the adult moth prepares to emerge, the pupa moves toward the opening, leaving a hole once the adult flies away.

Larval activity is highest during the peak growing season when the tree's vascular system is most active, providing the larvae with the necessary moisture and nutrients for growth.

The most reliable indicator of an infestation is the presence of "frass"—a mixture of wood shavings and larval excrement—piling up at the base of the tree or around exit holes on the bark.

Wilting and premature drying of the foliage at the tips of branches are common symptoms, as the internal boring prevents water from reaching the terminal growth.

Small, circular entrance or exit holes are often visible on the trunk and branches, sometimes accompanied by sap flow or gumming, especially in species like stone fruits.

Deformation of the bark or swelling in certain areas of the trunk can indicate that the tree is trying to wall off the tunnels created by the wood borer.

Observing the branches during windy weather can also reveal affected limbs, as they tend to snap easily at the points where the internal boring has weakened the wood the most.

Sanitation is the first line of defense: identifying and pruning infested branches early and burning or disposing of the wood correctly is crucial to prevent the spread of the moth.

For valuable trees, individual holes can be treated by inserting a systemic insecticide via a needle and syringe, followed by sealing the opening with grafting wax or putty.

Monitoring using pheromone or light traps helps arborists determine the exact timing for insecticide applications, focusing on the period just after egg-hatch.

Systemic insecticide treatments applied to the foliage or trunk can be effective in killing larvae as they ingest the vascular fluids of the treated tree.

Maintaining tree vigor through proper irrigation and fertilization is essential, as healthy trees are better equipped to withstand minor infestations and heal internal wounds more efficiently.