General information about caterpillars
The Oak Processionary Moth: what exactly is it?
The Oak Processionary Moth is the larva of a moth. That butterfly lays its eggs mainly in the tops of oak trees. There the eggs overwinter. They hatch from mid-April to early May. After molting several times, groups of caterpillars come together. They form large nests on the trunk and side branches of the oak tree. At night they go in procession in search of food in the tops of the tree, hence the name. Large groups of processionary caterpillars can eat a tree completely bare. The caterpillars molt three times, after which they develop fire hairs. The fire hairs cause health problems in humans.
Where did that caterpillar come from, a few years ago we never had any trouble with it?
About 30 years ago, the caterpillar was first seen in the Netherlands. There are many oaks in our country, so there is a lot of food for the caterpillar. Until three years ago, the number of caterpillars grew explosively, probably because the conditions were favorable. In recent years, the growth line has stopped and there are actually a lot fewer nests again. In the period 2019-2021, intensive control has been carried out with both pesticides and other ecological measures such as different roadside management and the use of tit boxes.
How many fire hairs does an Oak Processionary Moth have?
Each mature Oak Processionary Moth has about 700,000 invisible fire hairs with arrow-shaped barbs.
How do the fire hairs spread?
Distribution of the fire hairs is by air. Wind brings hairs as far as a hundred meters from the nest.
How do I recognize a nest?
Oak trees with Oak processionary caterpillars can be recognized by the spherical, white-gray nests on the trunks or thicker branches. The nests are dense coils of shedding skin with fire hairs and droppings.