Implications of not controlling slugs in oilseed rape and wheat in the UK

Metaldehyde is the main pesticide used to control slugs in oilseed rape and wheat in the UK. It is, however, often detected in raw water above the drinking water standard, with peaks following rainfall. Unless action is taken, regulatory restrictions, or even withdrawal, may be enforced. The Metaldehyde Stewardship Group has, therefore, introduced a voluntary pilot scheme. Two selected pilot catchments represent the first phase of measures where zero metaldehyde is advocated on the identified, ‘High Risk’ fields.

In the UK, approximately 59% of the total area of oilseed rape is affected by slugs. The estimated annual yield loss caused by this pest is 4% of the area affected; in some instances, yield losses may be much higher. Without pesticides, the calculated annual tonnage lost is 54,354 tonnes, costing the industry approximately £18 million per year (2.4% of the total crop value).

Approximately 22% of the total area of wheat in the UK is affected by slugs. The estimated annual yield loss caused by this pest is 5% of the area affected; in some instances, again, yield losses may be much higher. Without pesticides, the calculated annual tonnage lost is 153,280 tonnes, costing the industry approximately £25.5 million per year (1.1% of the total crop value).

It is calculated that the total annual cost to the UK industry from not controlling slugs in oilseed rape and wheat is approximately £43.5 million

In cereals, seed treated with the neonicotinoid, clothianidin, can help reduce seed kill but not later seedling damage. Cultural control options, including cultivation techniques and seed bed preparation, are already routinely carried out in most situations. Parasitic nematodes can provide a reduction in damage for about six weeks after application but success is dependent on wet conditions following application. This option is generally only economically viable for use in high value crops.