Safer scores for pesticides
Environmental aspects of sugar beet growing came under the spotlight at the International Institute for Beet Research Congress in Cambridge. Robert Harris reports
CONTAMINATION of underground water supplies by several widely-used sugar beet weed-killers is the main driver of a new Dutch initiative to guide growers to safer pesticide use.
It highlights potential problems with several new and established products, which could be lost if the system is adopted as EU legislation.
A scoring system based on EU measurements of environmental impact indicates the effects of herbicides on surface water and soil organisms, and their concentration in underground water.
Provided the score for any one does not exceed 100, the herbicide is deemed to be environmentally safe, says Jan Wevers, of the Institute of Sugar Beet Research in the Netherlands.
Examples of several commonly used herbicides scores shows they pose most risk to underground water by leaching (see table).
The scores are based on soils with a 1.5-3% organic matter content. Generally, the lower the organic matter the higher the risk. But clopyralid, lenacil and sethoxydim showed a high to very high risk at all organic matters, as do two new products, triflusulfuron-methyl (as in Debut) and quinmerac (soon to be introduced in the UK), Mr Wevers points out.
Practical mixes can be evaluated from that information, he explains. A normal low dose mix using 0.5kg/ha of phenmedipham, metamitron and ethofumesate on 1.5-3% organic matter soil scores 15 for surface water, 3 for soil and 49 for groundwater, passing the test.
But replace the metamitron in the first mix with 1kg of chloridazon/quinmerac and the score for groundwater shoots up to 1264. "If the weed control effect is similar, the first mix would be preferred," says Mr Wevers.
Although not proposed yet, Mr Wevers believes the system could be used as an EU registration guideline for new products and as a test for older ones. "If that happens, a lot of products could be lost to the grower."
Relative environmental effects of sugar beet herbicides