Large timberworm

The Large timberworm (Hylecoetus dermestoides) is a significant technical pest of wood belonging to the order Coleoptera and the family Lymexylidae. This beetle is notorious for its ability to bore deep into wood, causing substantial degrade to both living weakened trees and processed timber, making it a major concern for the forestry sector.

The beetle exhibits a wide host range, attacking various deciduous species such as oak, beech, birch, alder, aspen, and linden, as well as conifers like spruce and pine. It primarily infests wood that maintains a high moisture content, which is typical for recently felled logs, green timber, and storm-damaged trees in the forest or at sawmill storage yards.

The biological cycle is univoltine, meaning it completes one generation per year. In spring, adults emerge and oviposit on the bark. A unique feature of this species is its obligate symbiosis with Endomyces hylecoeti fungi. The larvae cultivate these fungi within their galleries; the fungal mycelium serves as their primary food source, rather than the wood tissue itself, facilitating rapid development within the timber.

The damage caused by larvae is characterized by circular galleries that extend deep into the sapwood and heartwood, perpendicular to the grain. As the larvae grow, they cause dark staining inside the timber due to the associated fungal growth. This damage is particularly detrimental to the wood quality, rendering the lumber unsuitable for furniture making, construction, or other high-value applications.

Effective management strategies focus on silvicultural practices and timber handling. Key preventive measures include the rapid extraction and processing of felled trees before the spring flight period. Storage areas should be managed to ensure low moisture levels, which inhibits the growth of the symbiotic fungi. Additionally, protecting stacked timber with insecticide treatments can be necessary in high-risk areas to prevent infestation.