Socio-economic study

Oak processionary caterpillars cause a whole range of damaging effects. As well as health issues, such as itching and eye and airway problems, the caterpillars also cause indirect problems including damage to oak trees, illness in pets and livestock, and the closure of camp sites, festivals, outdoor hospitality facilities and cycling and walking paths. In short, the oak processionary has a major socio-economic impact.

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  • Ecologie: eikenprocessierups gezondheid
  • Informatiebord in Maaseik
Linten eikenprocessierups

Cost/effectiveness analysis of the various control methods

We also investigated the cost of applying the various management methods. We included the costs of materials, supplies, and labor, and compared the cost of the various ecological management methods with each other and with the current cost of controlling pests using biocides.

The effectiveness (i.e., the reduction in oak processionary caterpillar numbers) of the various methods was assessed in a cost-benefit analysis.

We expect the ecological methods to significantly reduce labor costs, as they are much less labor-intensive.

The indirect costs—the impact on biodiversity of the various methods—were also mapped out.

Oak processionary caterpillar on oak leaf- Thaumetopoea processionea
Oak processionary caterpillar on oak leaf- Thaumetopoea processionea

To obtain the necessary data for the study, we consulted our Ambassador Community, 35 municipalities from the five provinces in the project area, who agreed to respond to an annual questionnaire about their oak processionary management.

What did the socio-economic study teach us?

The extensive survey among the ambassador community provided us with insight into the costs of various management methods and strategies used by the municipalities and the evolution of the associated costs over the four-year period.

  • Most ambassador municipalities combine preventive measures—primarily biocides—and curative techniques—such as vacuuming and manual removal—to control the pest, usually supplemented with one or more indirect (alternative) methods such as ecological mowing and hanging bird nest boxes.
  • Measured by the number of trees treated, preventive measures are, as expected, much cheaper (approximately €4.30/tree) than the more labour-intensive curative methods (approximately €37/tree). The number of trees treated curatively was therefore only a small fraction of the number of trees treated preventively.
  • A typical Ambassador municipality spent approximately €8,500 per year on preventive measures, €2,700 on curative measures, and €7,900 on alternative measures that could potentially impact the oak processionary.
  • Over the course of the project, preventive management costs decreased significantly as fewer biocides were used. However, curative treatment costs remained relatively stable.

Regarding the various strategies used—combinations of preventive, curative, and/or alternative measures—one important finding is worth noting: the municipalities that use only curative measures (such as vacuuming) spend only 45% of the budget of those who use both preventive and curative measures. This means that, regardless of the unit price and practical difficulties, it would be more efficient to invest in curative measures than in the more damaging preventive measures.

The analyses of cost vs. effectiveness and the impact on biodiversity show that:

  • Preventive methods such as biocides may be considerably cheaper, but curative methods are much more accurate and effective.
  • Preventive methods have a significantly greater negative impact on biodiversity than curative methods.
  • And, as expected, alternative methods scored much more positively on this aspect.