Alder Hook-tip

The Alder Hook-tip (Drepana curvatula) is a moth belonging to the order Lepidoptera and the family Drepanidae. This species is widely distributed across the Palearctic region and is recognized as a specific defoliator of hardwood trees.

The primary host plants for the larvae include alder (Alnus spp.) and birch (Betula spp.). While they show a strong preference for these genera, they are occasionally found on other broad-leaved trees. The larvae are considered pests in forestry, where they can affect the health and vigor of young stands and nursery stock.

The life cycle involves a complete metamorphosis with two generations per year in many areas. Adults emerge in spring and again in mid-summer. The pupae typically overwinter within cocoons constructed inside folded leaves or hidden between leaf layers on the host plant, providing protection against winter conditions.

Damage occurs when the caterpillars feed on the foliage. They use silk to bind parts of the leaves together, forming a shelter where they feed, which leads to skeletonized or ragged leaf margins. High population densities can cause significant defoliation, resulting in decreased photosynthetic capacity and increased susceptibility to secondary stressors like drought or disease.

Integrated Pest Management (IPM) is the most effective approach for controlling this pest. Strategies include:

• Regular monitoring of host trees to detect early infestation.
• Application of biological insecticides containing Bacillus thuringiensis during early larval stages.
• Preservation of natural predators, such as ichneumonid wasps, which act as important biological control agents.
• Use of selective contact insecticides only when infestation thresholds are exceeded.

By maintaining the biological diversity of the forest ecosystem, the pressure from Drepana curvatula can often be kept below the level where significant economic damage occurs to the timber or forest health.