Herbicide resistance is a challenge no farmer can afford to ignore. On many farms, Australia-wide, it is already having a significant impact on farm profitability through reduced grain yields, and increasing the cost of weed control. In some areas it is even threatening the viability of winter cropping as we know it.
Even though herbicide-resistant weeds are not yet having an economic impact on all cropping enterprises, they are present in every cropping area. Within Australia there is confirmed resistance to eleven different herbicide mode-of-action groups. Of the eight groups so far unaffected, only three are used in winter grain crops.
Failure to effectively control weeds can have an enormous impact on crop yield. In cereals where weeds such as wild radish, annual ryegrass or Indian hedge mustard are not effectively controlled early, yield potential can be reduced by as much as 45% (depending on the weed densities).
In an intensive cropping program, the typical approach has been to rely on one effective solution year after year until it stops working, then migrate to the next most cost-effective herbicide – which perpetuates the cycle of dependence. This over-reliance on a series of single solutions is resulting in the gradual loss of cost-effective chemistry and leading to higher production costs.
Potentially the most damaging effect of herbicide resistance is actually running out of options to control many agronomically important weeds. In the past, global R&D companies such as Bayer were very successful in discovering new mode-of-action herbicides regularly enough to keep farmers supplied with effective solutions. However there has only been one new herbicide mode of action introduced in Australia in the last 20 years – and another one is unlikely to come along anytime soon.
As many growers across the northern cropping region of WA have learnt, by the time herbicide resistance becomes apparent, it is already too late. What had been a cost-effective weed management tool can no longer do the job it once did.
All cropping areas are under threat, so – no matter where you are growing grain – there is an urgent need to use the full range of weed control products and other management techniques to slow the development of resistance and reduce its impact.
Herbicide resistant weeds represent the single largest threat to Australian and global food security and cost the Australian grains industry more than $200 million each year. Dr K Young, GRDC Program Manager - Plant Health Technologies, GroundCover Supplement, May-June 2013