Feathered thorn

The Feathered thorn (Colotois pennaria) is a moth belonging to the family Geometridae. As a pest in orchard and forestry environments, it is known for its larvae, which can cause significant defoliation on various deciduous trees if left unchecked during the spring growing season.

This pest affects a diverse range of host plants, predominantly pome and stone fruit trees such as apple, pear, and plum. In addition to commercial fruit crops, the larvae are often found on wild species including oak, birch, and beech, making the moth a common inhabitant of both managed orchards and surrounding woodland areas.

The life cycle of the feathered thorn consists of one generation per year. Unlike many other pests that overwinter as pupae or adults, this species overwinters in the egg stage. Eggs are laid in clusters on the bark of twigs during the autumn flight period. In early spring, these eggs hatch into larvae that immediately start feeding on opening buds and young foliage.

The damage caused by the larvae is characterized by the consumption of leaves, which can lead to complete defoliation of branches when populations are high. This loss of photosynthetic surface area weakens the trees, leading to reduced yield and poor fruit development. The larvae, typical of geometer moths, move in a distinct looping motion, making them easy to identify during inspection.

Effective management strategies include early spring insecticide applications specifically timed to the hatching period of the larvae. Monitoring the orchard in autumn for adult moths can help predict potential infestations. Furthermore, maintaining natural predators such as birds and beneficial insects, combined with good orchard hygiene like removing dead bark where eggs may be hidden, can significantly reduce the pressure from this pest.