The Prairie Star, MT
03-05-07
Sprayers can add flexibility, risk management to weed management
By TIM HOSKINS, For The Prairie Star
Sprayers can often be used by farmers to add some flexibility and risk management to weed management. The timing of application is critical.
If farmers rely on a custom applicator, their fields may not get sprayed in a timely fashion.
Bob Hartzler, Iowa State University Extension weed specialist, and Mike Owen, Iowa State University Extension weed specialist, say timing is the most critical part of any weed control program.
Owen says putting those sprayers to use at a different time can allow farmers to get more out of their weed control programs.
He says the program could start with an early pre-plant herbicide application. He says that can be done when conditions are not right for planting.
With using a pre-plant herbicide, he says a farmer is just trying to add some flexibility into the schedule in case there are any weather events, such as rain that would delay his next spraying application.
It also extends the window from one week to three to four weeks to get the next herbicide application done during a time close to planting.
“You have already killed most of the weeds,” Owen says.
He further explains as weeds get larger, they grow faster and then they get more competitive with crops. Therefore, he says using a pre-emerge herbicide kills weeds, and when the farmer returns to spray his post-emerge herbicide, the weeds are short and less competitive.
The size of the weeds allows some flexibility since the critical period has not been reached.
“Research has shown up to 1 percent of yield can be lost per day application is delayed once the critical period is passed,” says Hartzler.
The critical period is the point of time when weeds that emerge with the crop first begin to affect yields.
“Since we can't predict precisely the critical period, there is always risk of yield loss when relying on total post products and not having total control of when fields get sprayed,” Hartzler says.
Owen says using sprayers to add a pre-emerge herbicide application to the crop focuses attention on the need to have a strategy in any weed management system.
“It is not simple,” he say of any total post-emerge weed control system.