In recent years it has been a recurring theme: the nuisance caused by the oak processionary caterpillar. But the approach against the critters that cause itching and nuisance seems to work: so far this year oak processionary caterpillars have been found in 8 percent of the oak trees in the Netherlands, says the Knowledge Center Eikenprocessionierup. “This also seems to be the case in Drenthe, but it is true: the further north, the more often there is nuisance,” says Arnold van Vliet of the knowledge center.
There is no clear explanation for the greater nuisance in Drenthe and the other northern provinces. “We don’t know yet. That’s why we call on people to participate.” People have to look at at least thirty oaks and count how many trees the oak processionary caterpillar is in. “In the north it is true that it is less densely populated and that there are often endless oak avenues. That could play a role.”
The nuisance caused by the oak processionary caterpillar reached a peak in 2019, when a nest was found in at least 55 percent of the oak trees. At the time, only trees that had not been sprayed against the itch caterpillar were looked at. The current analysis also includes trees that have been sprayed.
Last autumn, the knowledge center already noticed that there were fewer oak procession butterflies. The researchers had therefore also expected the decline in the number of caterpillars. “There is still a lot to be done,” says Van Vliet. “The caterpillar is no longer leaving the Netherlands. The problem must be controlled. That means: don’t fight the caterpillar haphazardly, but look at where the risk locations are.” For this, municipalities must keep a close eye on the caterpillar, he says.
Most oak processionary caterpillars are often found in the Northern Netherlands. “This is due to a combination of circumstances,” says the biologist. “In general, we do see that the number of oak processionary caterpillars really increases if no action is taken.” In a ‘hotspot’ there is often a nest in every oak tree. In some places, people can still suffer from the caterpillars.
Due to storm Poly on Wednesday, there is also a good chance that nests of the caterpillar have been blown out of the tree. As a result, the caterpillars can end up on walls, in gardens or in other trees. Van Vliet points out that they are still dangerous because of the stinging hairs. Those fire hairs can cause itching, bumps and eye complaints.