Yellow-horned moth

The Yellow-horned moth (Achlya flavicornis) is a moth belonging to the family Drepanidae, order Lepidoptera. This species is commonly found throughout the temperate regions of Europe and parts of Asia, where it acts as a specific defoliator of deciduous trees.

The primary host plants for the larvae are species of birch (Betula), though alder (Alnus) may also serve as a food source. Due to their specific host preference, outbreaks of this moth can lead to localized severe defoliation in birch-dominated woodlands, urban landscapes, and forest nurseries.

The life cycle is univoltine, meaning there is only one generation per year. The species overwinters as a pupa within a tough, silk-lined cocoon buried in the soil or leaf litter beneath the host tree. Adults typically emerge in early spring, often before the full foliage appears, with the moths actively laying eggs on the twigs or buds of their host.

Damage is caused entirely by the larval stage. Upon hatching, the caterpillars feed on developing buds and young leaves. As they mature, their consumption rate increases, leading to extensive leaf stripping. Persistent defoliation causes the tree to lose its photosynthetic capacity, resulting in reduced growth, weakening of the tree's health, and increased susceptibility to secondary pests.

Effective management requires a combination of monitoring and intervention. Foresters often monitor adult population levels using pheromone traps early in the season. If scouting reveals that the larval density exceeds the economic threshold, treatments with selective bio-insecticides containing Bacillus thuringiensis are recommended. Cultural practices, such as maintaining healthy tree diversity and protecting local populations of insectivorous birds, are also vital for long-term control.