Develop Effective Strategy To Avoid Herbicide Resistance

Develop Effective Strategy To Avoid Herbicide Resistance

Iowa farmers are encouraged to follow these tips to help preserve benefits of herbicide-tolerant crop technology.

Glyphosate has been called the world's greatest herbicide. Its overwhelming acceptance has made it the most widely used product on the market today. Dr. Stephen Powles, world-renowned expert on weed resistance, takes it one step further saying glyphosate is to weed control in agriculture as penicillin is to disease and infection treatment in medicine. Both are considered miracle products and given the distinction of being a "once-in-a-100 year discovery."

RESISTANT WEEDS: Farmers need to change their weed control strategies to help preserve the benefits of herbicide-tolerant crop technology. Resistant weed populations are continuing to increase, for several reasons. "Diversify your weed management," advises Mark Grundmeier, an agronomist for Latham Seeds. "Rotation of crops as well as rotating the use of herbicides with differing modes of action would be wise move."

Herbicide-resistant weed populations are continuing to increase, especially common waterhemp, marestail and giant ragweed. Mark Grundmeier, product manager for Latham Hi-Tech Seeds, says it's due to farmers' management decisions. Resistance to glyphosate-based herbicides is going to show up if you are using those herbicides as the only source of weed management. He notes there is no simple solution to weed resistance issues, but rotation is one common management practice that can certainly help.

Development of weed resistance to herbicides can be slowed down, or even stopped

"Weed resistance can be significantly slowed down or even averted altogether with careful crop and herbicide use plans," says Grundmeier. "Bring LibertyLink or conventional soybeans into your rotation. Likewise when planting corn, plant conventional or straight LibertyLink hybrids. Using herbicides that have different modes of action is critical."

Many weed scientists in the Midwest say there are basic steps every farmer should take to prevent the onslaught of herbicide-resistant weeds. Grundmeier's suggestions:

* Know your weeds, know your fields. Closely monitor problem areas that have tough-to-control weeds or escapes or misses. Scout early in the spring and throughout the season. Be on the lookout for large-seeded weeds like giant ragweed, sunflower and cocklebur. These weeds are always tough to control and should never be allowed to get established.~~~PAGE_BREAK_HERE~~~

Don't forget weeds can and do exist in untilled fields and if these weeds aren't managed prior to or immediately after planting, they can threaten future yields and cause unnecessary and potentially, costly headaches. It's also important to start with clean fields. Use tillage, residual herbicides and/or burndown applications of herbicides to control all emerged weeds before planting. Early season weeds rob yields you cannot see at harvest. Crops have a better chance of reaching optimal yield when they're not competing with weeds for sunlight, water and nutrients.

* Diversify control tactics. Use more than one tactic or herbicide to control weeds. Tank mixes of herbicides with different modes of action will help control the weeds of concern and are better than rotation of modes of action.

* Apply herbicides correctly. Proper application methods and rates are crucial to season-long control. The three most important factors are timing, timing and timing!

* Soil-applied residual herbicide. Use a soil-applied residual herbicide on all acres regardless of crop or trait. Whether or not you plan to till the fields, include a residual herbicide that controls weeds that will germinate first, are most populous and are of greatest concern.

* Know your herbicides. It's imperative to know what herbicides you are using, what they control (and do not control), what replant restrictions exist and whether there is significant potential for crop injury.

* Reduce the seed bank. Surviving weeds must not be allowed to set seed and thereby become the dominant weed species. Farmers can reduce the seed bank of resistant weeds with a fall burndown and residual program.

* Clean equipment. Prevent the spread of resistant weeds at all cost by cleaning tillage and harvest equipment before moving from fields infested with weeds to those that are not.

Grundmeier encourages farmers to be proactive and manage weeds before they become a problem. Most importantly, manage herbicide resistance before it becomes a major problem. "You do that by diversifying your tactics," he says. "Weeds are becoming a greater challenge for farmers every year and without new technology and solutions, these tough-to-control weeds will cause agriculture to take a step backwards. Herbicide-resistant weeds must be addressed now to preserve the benefits of herbicide-tolerant crop technology." Visit or blog for more information.

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