Growers warned they must reduce reliance on herbicides.

Speaking at the HGCA/PRGO Oilseeds and Pulses Conference on 26 January, Sarah Cook, research consultant for ADAS has painted an uncertain picture of the future for some herbicides in UK farming. Cook explained that herbicides were increasing in price, while failing to deliver the same level of protection.image expired

Furthermore, she revealed that some commonly used herbicides, such as carbetamide and propyzamide, were being detected in watercourses above their acceptable legal limits of 0.1mg/litre and as such their suitability for future use has been brought into question.

In summer 2009, the HGCA Information Sheet highlighted the potential for water contamination of certain herbicides; it advised growers to take measures to minimise this risk. These measures included establishing grass buffer strips with a width of at least 6m beside water courses in the seasons before oilseed rape, only spraying in suitable weather (neither overly dry, nor wet) and minimising dose rate if possible.

The 2009 information sheet also carried warnings that, “Unless the industry adopts new measures to minimise oilseed rape herbicides reaching water, these products may be withdrawn... this would threaten the viability of growing oilseed rape in the UK.”

However, as herbicide resistance is increasing and there are only a small number of new herbicides under development, Cook has warned growers that they need to explore other options for weed management and has stressed that herbicides should be used as a last resort.

Her suggestions for alternative weed management include drilling into a stale seed-bed, optimising seed rate, increasing crop competition and altering sowing date and using mechanical weeding, although with this last option there are a number of factors to consider to avoid damaging crops.

Dr Cook advocates, “Early passes in the direction of drilling”, and has warned that, “later passes are more damaging to the crop, so as the crop gets bigger, the damage increases.” 

The HGCA’s weed control page provides information and resources for maximising herbicide performance and good weed and resistance management; it is accessible here