Doetinchem: biological control of the oak processionary moth

There are many oak trees in the forests and plantations around Doetinchem. Marc van Rijswijk is the spokesman for Buha, the implementing organization for the Municipality of Doetinchem whose responsibilities include green management. Buha manages some 9000 solitary oak trees withing this municipality. In 2020 the level of infestation with the oak processionary caterpillar within the built-up area was so high that preventive management became necessary. ‘We think it is important to maintain the biodiversity in the centre, and public opinion is quite sensitive to spraying here. We worked in consultation with distributor Mertens and decided that in spring we would start using Koppert’s nematode product Entonem. A major advantage is that the bycatch of other caterpillars is much lower, which is a great benefit to biodiversity. In mid-April, we started using nematodes at locations with significant contact options within the built-up area. For the optimal effect, we did it twice.’

Entonem an important link

Van Rijswijk is confident that the use of nematodes helps to reduce the level of infestation. ‘By using Entonem and extracting the nests as a curative measure, we can keep the situation manageable for now. In the longer term, improving biodiversity will have an important role to play – breaching the monocultures of the oak and stimulating the natural enemies of the oak processionary caterpillar. As already stated, the use of nematodes is an important part of this. Entonem is without doubt an important link in ensuring manageability of the oak processionary caterpillar.’