News - June 3, 2020

Study of how to combat caterpillar

Roelof Kleis

WUR will be investigating how to improve pest control of the oak processionary caterpillar.

©Roelof Kleis

The pestiferous caterpillar has been in the Netherlands for decades. Municipalities plagued by them have come up with all kinds of solutions for tackling the pest, some more successful than others. There is no comprehensive approach, although there is a guide advising municipalities on the different methods. But the evidence supporting that advice is weak. A new study intends to change that.

A consortium of 20 different parties, including the WUR Oak Processionary Caterpillar Expertise Centre, 11 municipalities and the Society of Forest and Nature Landowners, are involved in the study, which is funded by the Horticulture Top Sector. WUR and the Expertise Centre will be carrying out the study, which is headed by ecologist Joop Spijker.

We will need to learn to live with the caterpillar
Joop Spijker, ecoloog

‘We will need to learn to live with the caterpillar,’ says Spijker. So the aim of the study is not to eradicate the caterpillars. ‘That is no longer possible anyway. But we can improve the approach.’ That starts with information on how numbers of caterpillars and moths are changing. In the 11 participating municipalities, a standardized count will be conducted this year and next.

GP visits That will enable a comparison of the effectiveness of different pest control methods used by the municipalities. Spijker will also use pheromone traps to monitor the moths. In addition, they will assess health complaints in partnership with the healthcare institute NIVEL. Spijker: ‘We want to connect the number of caterpillars to GP visits. This will give an impression of the societal impact.’


That impact is important for policymakers when they have to take decisions about measures to combat the caterpillar. The ultimate goal of the two-year study is a new guide. Spijker: ‘One with recommendations backed by evidence on what works and what doesn’t. That could mean more advice on effective measures that offer value for money and don’t harm biodiversity.’

Three WUR researchers will be involved in the study: Spijker, biologist Arnold van Vliet (from the Expertise Centre) and Hidde Hofhuis (Environmental Systems Analysis).