Curative Control of Wireworms (Agriotes spp.) in Potatoes
Photo: Floriane Bussereau,
Agroscope
When wireworm damage to potato tubers is excessive the crop ceases to be marketable. Various control options were explored in an effort to remedy the problem.
Wireworm damage to potatoes
Wireworms – also known as click-beetle larvae – are highly polyphagous pests capable of causing major damage in various crops, including potatoes. The larvae tunnel into the tubers, adversely affecting the quality of the harvest. When the proportion of potato tubers damaged by this pest becomes excessive, the harvest fails to achieve its proper value, leading to major economic losses for producers. Although various plant protection products were used in the past to control wireworms, their authorisations have been revoked. Currently, an effective solution is no longer available to farmers in Switzerland.
Control efficacy of plant protection products
Agroscope conducted pest control trials from 2015 to 2019 to study the efficacy of various chlorpyrifos-, spinosad-, spirotetramat-, tefluthrine-, fipronil-, Metarhizium brunneum- and Beauveria bassiana-based plant protection products in controlling wireworm damage in potato tubers. Three different application periods were studied: that of the catch crop preceding the potatoes, the potato-planting period itself, and the six weeks post-planting.
The results obtained show that, regardless of the period of application, the tested products failed to significantly reduce wireworm damage to the potato tubers compared with the untreated control. However, the fipronil-based reference product, which exhibited a high level of efficacy, was an exception to this rule.
The importance of application period for the fipronil-based treatment
The control period played a key role in the level of efficacy of the latter product. When fipronil was applied in autumn in the catch crop preceding the potatoes, the proportion of tubers with wireworm damage was markedly lower than that of the ‘control during potato planting’ modality. Moreover, the rate of damaged tubers was 7% lower than the threshold of acceptability for the marketing of the crop.
Conclusions
- Wireworms cause major damage in potato crops.
- Apart from the fipronil-based reference product, which is banned in Switzerland and in Europe, the anti-wireworm products tested failed to demonstrate efficacy in reducing damage to the tubers.
- The period of implementation of the control measures plays a key role in their success and must be taken into consideration in future research. The said period may vary according to the nature of the plant-protection product.
- The option of control measures over the entire rotation is an interesting prospect to explore, particularly in the case of entomopathogenic fungi.
Bibliographical reference
Essais de lutte contre les vers fil de fer (Agriotes spp.) dans la pomme de terre en Suisse.
