Autumnal moth

Systematic position: The autumnal moth (Larentia autumnata) belongs to the order Lepidoptera and the family Geometridae. It is a well-known forest pest in the temperate regions, notorious for its periodic outbreaks that can cause widespread defoliation in boreal and temperate forests across Europe and North America.

Host plants: The moth is polyphagous, primarily feeding on deciduous tree species. Its preferred hosts include birch (Betula), alder (Alnus), willow (Salix), and various fruit-bearing trees such as apple and plum. Due to its wide host range, it represents a significant risk to both forestry and commercial orchards.

Biology and life cycle: This species is univoltine, meaning it has one generation per year. Adults emerge and fly during autumn, usually from September to October. Females deposit eggs on the bark of host trees, which then overwinter. In the following spring, larvae emerge synchronously with the budburst of the host tree, allowing them to access the most nutritious plant tissues immediately.

Nature of damage and pest status: The larvae are the damaging stage of this insect. They initially skeletonize leaves, but as they grow, they consume entire leaf blades. During outbreak years, the insect density can be high enough to completely strip trees of their foliage. This causes severe physiological stress, stunted growth, and in severe cases, the mortality of weakened trees.

Control measures: Managing the autumnal moth requires an integrated approach to minimize economic and environmental impact. Effective strategies include:

• Monitoring of egg density during winter to forecast outbreaks.
• Application of biological insecticides such as Bacillus thuringiensis during the early larval stages.
• Use of sticky or mechanical barriers on trunks to prevent larvae from climbing.
• Promoting the biodiversity of natural enemies like parasitoid wasps and birds.