August 1, 2007 | By: Laura Skillman

What makes a weed, a weed? Generally, it is a plant that competes with the crop in a field. This year some of those weeds were not what you might think. They were wheat and corn plants.

“I believe this is one of those seasons that is going to stick in the minds of farmers,” said Jim Martin, weeds science specialist with the University of Kentucky College of Agriculture. “It’s been a challenge for people in a lot of different ways and no doubt weed control has had its moments too.”

Martin highlighted some of these challenges during UK’s recent field day at the Research and Education Center in Princeton. One such challenge was in destroying freeze-damaged wheat to replant another crop. Wheat and some grasses can be killed very easily when it is young but becomes more difficult to kill once it has begun tillering. That was the state of Kentucky’s wheat crop when the freeze took place in April.

Martin said having to kill fields of wheat was not something he’d dealt with before. Some herbicide options worked better than others, he noted, and required patience. 

The freeze also killed some cornfields but not every plant in the field, so these also had to be managed in order to replant. For people who followed the strategy of using non-glyphosate resistant corn in their early planted fields, in case of a freeze, that strategy paid off. The field could be replanted with a glyphosate resistant variety then sprayed with the chemical to destroy any of the remaining plants from the first planting. 

Farmers who planted resistant varieties had to turn to other options that were not as simple. In many cases the damaged corn didn’t have a lot of growth on it, lessening the chances of some chemicals working effectively. These were more effective if farmers allowed the surviving corn to recover somewhat and begin some regrowth before spraying it with an herbicide.

Other farmers did nothing and felt like they could manage the damaged corn fields simply by having their row cleaners rip out the damaged plants as they replanted the field, Martin said. This strategy did not work as well as some had hoped. 

In terms of more traditional weeds, marestail was a problem this year in soybeans. Martin said this could be attributed to the warm February and March that allowed the weed to grow more rapidly than in a more normal year, making it more difficult to combat. Then, if farmers used 2-4D to control it and sprayed close to the April freeze, they probably did not get the control they would have under more spring-like temperatures. Rescue treatments don’t work well in trying to combat this weed.

Wheat goes a long way in managing marestail, Martin said. Putting wheat into the cropping rotation can help alleviate the weed in many fields.

“It’s not a cure-all, but a good stand of wheat goes a long way in suppressing marestail,” he said.

Weed management can be challenging, but UK specialists work to provide the latest information for Kentucky’s farmers. Information on weed management can be found at local offices of the UK Cooperative Extension Service.


Jim Martin, 270-365-7541, ext. 203