Herbicide-resistant weeds in Europe: the wider implications

Herbicide-resistance occurs in 55 weed species in 21 European countries. 91% of cases are associated with just four herbicide mode of action groups: ACCase and ALS inhibitors, and triazine and urea/amide photosynthetic inhibitors. There are also a few cases of resistance to bypiridiliums, dinitroanilnes and synthetic auxins. Resistance to ALS inhibitors tends to be less prevalent in Europe than elsewhere, but is likely to increase. A small scale survey showed that Alopecurus myosuroides is considered to be the most important herbicide-resistant weed in Europe at present. Lolium spp., and to a lesser extent Papaver rhoeas and Avena spp., were also highlighted as being of major importance in many countries. One consequence of the ongoing EC review of pesticides may be a reduction in the range of modes of action available to European farmers. This may reduce the opportunities for rotating different modes of action as a method of reducing resistance risk. Greater dependence on high resistance risk herbicides, such as ACCase and ALS inhibitors, because of lack of alternative modes of action, is likely to increase the incidence of resistance in grass-weeds.