In the Furrow
Herbicide Resistant Pigweed a Continuing Problem
By Peyton Sapp County Extension Coordinator

No one knows better than farmers that herbicide resistant

pigweed continues to be one of the most probl ematic weeds we have ever seen. The herbicide resistance

issue

did not pop up overnight, nor will we get rid of the problem in short order. The technology is there to control herbicide resistant weeds, but we have to be willing to invest the time and/or money it takes to get the upper hand.

Glyphosate resistant palmer amaranth is here in Burke County and the verdict is still out on a resistance that has been developed to ALS inhibitors. Many producers continue to comment on the problems they are having with control of pigweed. Dry weather has compounded problems as it reduces herbicide efficiency and decreases effectiveness. So, what do producers need to do?

A weed's ability to develop resistance is determined by a number of factors. The three known mechanisms by which plants develop resistance are:
1.) Altered site of action
2.) Altered Metabolism
3.) Sequestration

A plant that is able to survive a herbicide treatment that would normally kill it has utilized one of these mechanisms to survive. Herbicides that have a single mode of action, that are used multiple times during a growing season, that are used for consecutive growing seasons, and herbicides that are utilized with no other weed control strategies are more likely to have weeds develop resistance.

So, in the case of herbicide resistant palmer amaranth, producers need to be aggressive with their weed control strategies. An effective herbicide resistant weed management plan will require the integration of multiple herbicide chemistries. Be sure that you include pre-plant or at planting herbicides and develop a plan that includes herbicides with different modes of action. Mechanical cultivation is always an option. The price of diesel is high, but the cost of not being able to control certain weed species

may be higher in the end! I mentioned we had the technology

to control resistant weeds. I guess the "old hand pulling weeds" may not be what first came to mind. However, this is something that many have to resort to, and it may turn out to be something more we will have to do to get control of resistant pigweed.

Herbicide resistant weeds are a huge problem. However, they are not some "monsters" that are out there with no way to take them out. It will cost money, time and extra effort to get control of species like resistant pigweed. Extra production costs are not something we want in this time of record high input costs, but producers have to work aggressively to stop herbicide resistant weeds.