Oak processionary moth

The Oak processionary moth (Thaumetopoea processionea) is a moth belonging to the Notodontidae family. It is widely recognized for the distinct behavior of its larvae, which march in long, single-file processions to move between their communal nests and the foliage of host trees.

This pest primarily infests oak species (Quercus), including common oak and sessile oak. While they show a strong preference for oak, large outbreaks can cause the larvae to spread to neighboring deciduous trees, leading to significant defoliation of forests, urban parks, and landscape plantings.

The lifecycle consists of one generation per year. Eggs are laid in clusters on the bark of twigs and over-winter in this stage. Larvae emerge in spring and go through several instars. They build conspicuous white silk nests on the trunks and branches of trees, which serve as their shelter during the day as they emerge at night to feed.

The economic and ecological impact is severe, as repetitive defoliation weakens trees, making them susceptible to secondary pests like bark beetles or fungal pathogens. Furthermore, the larvae are covered in thousands of tiny, venomous hairs containing a protein called thaumetopoein, which poses a significant health hazard to humans and domestic animals, causing skin irritation and respiratory distress.

Integrated pest management (IPM) practices for control include:

• Physical removal and destruction of nests using specialized protective gear.
• Biological control through the application of Bacillus thuringiensis, which is specific to caterpillars.
• Use of pheromone traps to monitor adult male moth populations and inform treatment schedules.
• Encouraging natural predators such as parasitic wasps and predatory beetles to regulate caterpillar numbers.