Abstract
The incidence of wireworm (click beetle) damage on potato in the UK is on an upward trend, both in traditional risk situations following long-term grass, and where crops are grown in fields in all-arable (no grass) rotations, known as ‘arable wireworm’. This is particularly serious for major UK potato growers, packers and processors, as even low wireworm populations can cause a severe loss of tuber quality. This can make the difference between a crop worth >£100/tonne, or one ploughed in at a significant loss. Because of this risk of total crop failure, some potato growers now regard wireworms as a more serious issue than potato cyst nematode. Wireworms are polyphagous, and in the UK carrot, sugar beet and leek growers have also been affected, although damage levels in cereals (which are less susceptible than many root crops) are not currently causing concern. The reasons for the apparent increase in the importance of wireworm populations (principally Agriotes obscurus, A. sputator and A. lineatus) are likely to include a combination of agronomic, cultural and ecological factors associated with changes in cropping practice in farming that have occurred over the last 10 to 15 years (Parker & Howard, 2001). While wireworm risk assessment has recently advanced throughout Europe (including the UK) via the development of pheromone trap systems (Furlan & Toth, 1999; Furlan et al., 2002), the ability of the potato industry in particular to manage wireworm populations to prevent crop damage both rotationally in the long-term and, particularly, in the potato crop has arguably not significantly progressed for the last 50 years. This is partly due to the fact that no new suitable chemistry has been forthcoming which combines the required soil persistency with an acceptable environmental profile, but the biological and technical knowledge base required to implement an effective IPM strategy for wireworms, encompassing both rotational (wireworms take four years to complete their development in the soil) and short-term (in-crop) management, is also poor. The rotational element in particular has been largely hitherto ignored, but is a critical issue for those growers with a persistent ‘arable wireworm’ problem – a situation that is becoming more common. On a biological level, two significant scientific obstacles hinder the development of sustainable control options. These are our inability accurately to identify wireworms to species which limits our ability to interpret population processes at a fine scale, and at a landscape level, the lack of understanding of adult dispersal potential (highlighted by issues surrounding the interpretation of pheromone trap catches) and hence the importance of population refuges in non-farmed land. In addition, our knowledge of the potential of a range of novel control options is limited – a situation that the UK has is in common with other areas of Europe and North America where wireworms are significant pests. Sustainable wireworm management can only be achieved through a concerted research effort aimed at improving the biological knowledge base (particular with regard to adult beetles) and expanding the range of potential control options.
United Kingdom