ETH Zurich

Public and Private Extension Influence Pest-Control Strategies

Does it Matter Who Advises Farmers? Pest Management Choices with Public and Private Extension. (Open Access)

Fruit and wine producers who receive information from the public sector are more likely to use preventive measures such as nets or hygiene measures to combat spotted-wing drosophila. Producers advised by private firms that sell plant-protection products are more likely to use synthetic insecticides.

The spotted-wing drosophila can cause significant damage in fruit production and viticulture, and its control requires the implementation of costly measures (Knapp et al. 2020). Although a wide range of measures are available to producers to combat this pest, none of them is completely effective on its own, and not all measures are always cost-effective. Moreover, there is great uncertainty as to the efficacy of the individual measures, since the spotted-wing drosophila is a relatively new pest, and only limited experience regarding its control has been collected to date. Frequently used pest-control strategies in fruit production and viticulture include the following in particular: (i) preventive, non-chemical measures (such as nets, customised harvest management practices, various hygiene measures), and (ii) the use of synthetic insecticides*. All other things being equal, preventive measures reduce pest pressure, thereby contributing to lower insecticide use.

Survey on the Spotted-Wing Drosophila Control Strategy

In repeated surveys conducted over the period 2016–2018, Swiss cherry, plum, berry and wine producers were questioned on the strategies they chose to handle spotted-wing drosophila (the survey was conducted in all parts of the country, see Knapp et al. 2020). In addition, details were gathered as to whom producers received their information on handling the spotted-wing drosophila from. Producers could choose from various categories, including in particular information sources from private firms selling plant-protection products (plant-protection product manufacturers, marketing and sales stakeholders) and the public sector (e.g. cantonal extension services, but also Agroscope channels and events). In the analysis, the use of information sources from the public sector is always associated with additional effort (e.g. attending an event, actively making contact, subscribing to a newsletter). Multiple mentions were possible. We used data from 733 non-organic farms, and investigated by means of regression analyses the connection between (i) the use of preventive measures and (ii) the use of insecticides on the one hand, and the information and extension channels used by the producers on the other. Here, numerous other factors influencing the chosen strategies were controlled for. We also corrected in the analysis for various sources which might distort the results – for example, for the fact that farms making use of advice from private firms differed structurally (e.g. in terms of size and specialisation) from those seeking advice in the public sector.

Public Extension Increases the Use of Preventive Measures

All of the analyses deliver a clear and robust message: producers who receive information and advice from the public sector are (9–10%) more likely to use preventive measures (e.g. nets, hygiene measures), whilst producers receiving information from private firms selling plant-protection products are (8–9%) more likely to use synthetic insecticides.

* See also ‘Details der Task Force Drosophila Suzukii’ and Wüpper et al. (2020) for the list of the measures enquired about here. In addition, the stone meal kaolin plays an essential role in some crops (especially vine crops) in preventing drosophila attack, without incurring any risks for humans and the environment. We find no difference in kaolin use depending on whether the producer uses a public or private information and advice channel.


Further information

This article appeared in a similar form in the Agrarpolitik [=’Agricultural Policy’] Blog at David Wüpper and Robert Finger are in the Group for Agricultural Economics and Policy at the ETH Zurich. Nikolaus Roleff was a Master’s student in the Group. Contacts: Robert Finger, & David Wüpper,


Knapp, L., Mazzi, D., Finger, R. (2020). The economic impact of Drosophila suzukii: perceived costs and revenue losses of Swiss cherry, plum and grape growers. Pest Management Science. In Press (open access)

Möhring, N., Ingold, K., Kudsk, P., Martin-Laurent, F., Niggli, U., Siegrist, M., Studer, B., Walter, A., Finger, R. (2020). Pathways for advancing pesticide policies. Nature Food 1, 535–540.


  • Producers receiving information and advice from the public sector are more likely to use preventive measures (e.g. nets, hygiene measures), whilst those receiving information from private companies selling plant-protection products are more likely to use synthetic insecticides.
  • Extension, education and information services must consider the negative external effects of plant-protection product use on humans and the environment. The use of alternative, preventive strategies that prevent pest pressure and have lower external effects must be strengthened.
  • Independent advice and information from the public sector plays a key role here. It can therefore serve as a useful supplement to private activities.
  • Alternatives to the use of plant-protection products can be made more attractive e.g. by increasing the efficacy of preventive strategies and reducing costs.
  • All this should form part of a holistic plant-protection product policy (see Möhring et al. 2020).
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