Pest Risk Analysis for Western Corn Rootworm (Diabrotica virgifera virgifera)
1. Western corn rootworm (WCR), one of the most important maize pests in North America, and increasingly important in central Europe, has been found in the south east of England. The pathway by which WCR arrived in the UK has not been identified although there appears to be a link with international air transport.
2. WCR is primarily a pest of continuous maize. Approximately 120,000 ha of maize are grown each year for silage, of which an estimated 20% is continuous. A much smaller area of maize is also grown for grain production, sweetcorn, and as game cover. A small proportion of larvae can develop to adults when fed on cereals such as wheat and barley but more research is required to determine how fecund (fertile) females developing from these alternative hosts would be.
3. As the UK climate warms conditions are becoming increasingly suitable for WCR to establish in a larger portion of the UK maize crop. By 2050, all of the UK maize crop is likely to be vulnerable.
4. Although WCR can establish in southern England under current climatic conditions, population densities are likely to remain low unless the area of continuous maize increases from its current level.
5. Experiences in central Europe, where the summers are significantly warmer and WCR has been present for over ten years, suggest that significant economic impacts, due to larvae feeding on roots causing yield losses and crop lodging, only occur after several years of continuous maize cropping. Crop rotation is the most effective means of controlling WCR and in regions where WCR has caused significant damage some European farmers are now switching to growing maize in rotation.
6. A range of alternative management options for control or eradication of WCR have been used in areas where the pest occurs. Of the three insecticides approved for use in the UK only chlorpyrifos (an organophosphate) has been shown to be effective against WCR. However, the use of this chemical is under review in the UK and its future availability cannot be assured.
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- United Kingdom