I'm often asked the question: "Who is to blame for the development and spread of herbicide resistance in weeds?" Seeing as I am neither a lawyer nor a politician, I am not in the habit of pointing fingers and laying blame. Mostly, I just rephrase and redirect the question: "Who is responsible for preserving herbicide susceptibility in weeds?" The answer is easy and egalitarian: "We all are." If you really want to trip me up, ask me: "How do we preserve herbicide susceptibility?" Ummm…
Do you want me to give you the strict scientific game plan? Simple. Rotate crops, rotate chemistries, rotate strategies, etc…the best advice for managing your farm is the advice that you would employ in managing your bank account: diversify. Integrated weed management, we call it.
But, let's face it, this is often easier said than done. This is because herbicide susceptibility is, in essence, a collective (or common) property, not an individual one. Herbicide susceptibility is not limited to ONE farm, county, or region; rather, it is SHARED by a larger population of agricultural entities (and by this I mean growers, industry and commodity groups, and research scientists) over both time and space. And common property is inherently prone to a lack of stewardship - a phenomenon described as the 'tragedy of the commons.'
To actively preserve susceptibility, everyone involved must be willing to accept the economic costs that will likely be incurred; often, preventative herbicide programs are expensive, especially in the short-term. This also means accepting that new and alternative chemical technologies may not be available in the near future to replenish old, expired ones. Another hurdle to overcome is the sense of futility that can develop upon the realization that herbicide-resistance can be a mobile trait; pollen and seeds are capable of dispersing herbicide resistance over long distances.
The assumption that persons who invest in resistance management programs will reap the benefits (i.e. delayed occurrence of herbicide resistance) may, sadly, be inaccurate. The movement of a resistance trait across the landscape (via seed and pollen) may make growers unwillingly to spend time and money implementing herbicide resistance management programs. Why should one person work to preserve susceptibility if their less-than-diligent neighbor allows herbicide resistance to flourish?
So how do we all get on the same page? Do we use carrots (industry- or government-led incentives)? Or sticks (mandates)? I don't know. I'm hoping that someone smarter than me will reveal the secret. What I do know is that I, as a scientist, need to think BEYOND the science. I know that I need to think about the economic and social factors driving the prevention/development of herbicide resistance. We all do. That's when we'll truly have an integrated management plan.
For more thoughts about the human dimension of weed control, see a previous blog post by Brad Hanson (http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=4988).
Also, feel free to check out an article Dr. Ted Webster (USDA-ARS) and I wrote entitled "Loss of glyphosate efficacy: a changing weed spectrum in Georgia cotton." Weed Science (2010) 58:73-79.
