The oak processionary will not leave

Wednesday 24 June 2020 by Frank Jansen

No one will have missed it: the oak processionary is back. Last year it dominated the news all summer. This year the coronavirus of course changed that, but even now the annoying caterpillar is frequently in the media. And it is likely that this will continue to be the case in the coming years.

700,000 hairs per caterpillar

Each caterpillar has no less than 700,000 hairs, which can cause bumps, itching and even respiratory problems when they whirl out of the tree. Scratching doesn't work, working your skin with tape to pull out the hairs does. Here and there you will find many more tips. The problem is certainly not something of the last few years. On cycling forums people have been complaining about it since 2012.

Last year, however, the situation escalated and the caterpillar was the story of the day for weeks. 

It became clear that the plague was caused by a combination of 3 factors:

  1. Climate change: the caterpillars love heat.
  2. Too many oaks. In many European countries we simply planted far too many oaks. This is easily explained, because an oak provides good firewood and the wood is also often used to make furniture, for example. Moreover, it is a solid wood, so the trees don't blow over easily.
  3. There is less and less room for natural enemies, such as birds, beetles and wasps. This is also the reason why the nuisance in forests is much less than along neatly mowed avenues.

European problem

The oak processionary is not only a problem in the Netherlands. A search through the international news results in numerous news items from Italy, Germany ("Eichen-Prozessionsspinner"), Belgium, France and Luxembourg. In the Netherlands, this year's reports appear to be slightly less numerous than last year. Many municipalities have taken substantial measures this year. For example, a lot of effort was put into specialised companies that suck up the caterpillars. Thousands of nesting boxes have been hung to attract birds. Roadsides are mowed less quickly, which gives insects more space. Yet when you cycle through the landscape you can still see many of the characteristic red marking ribbons. But it never takes long before you see an aerial work platform with a completely wrapped worker.

Too little, too late?

The question is whether it's enough. Experts don't think so. The oak processionary is here to stay. There is no quick fix. According to many experts, sucking out caterpillars is just a drop in the ocean. They believe in a greater diversity of the type of trees and stop the tightly mowed verges. This year, the municipality will once again have to critically analyse their measures. In this respect, we see a parallel with the corona approach in various countries. Every municipality has a different approach, just as every country has its own approach to controlling the corona virus. Time will tell what works best.

We continue to follow the oak processionary.

Pictures: Frank Jansen

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