Rainy and warm weather during 2015 will mean widespread weed problems this spring in Iowa. Growers can thank last year’s weather patterns for the weed challenges ahead. The flooding of many soybean fields during summer of 2015 means more movement for weed seeds, and all signs point to the need for a ramped-up weed management plan in advance of planting.

“As there’s more water, weed seeds tend to shift around more than in dry years,” says John Pawlak, product development manager for Valent U.S.A. Corporation, maker of Valor, Valor XLT, Fierce and Fierce XLT herbicides.

WEED WATCH: Applying preemergence residual herbicides is the only way for growers to get their fields off to a healthy, productive start. Full labeled use rates of multi-effective modes of action are most important for soybean growers to keep in mind this spring.

And, the unseasonably warm start to winter in Iowa at the end of 2015 allowed winter weeds to grow a lot longer than they normally would, so those are expected to be more difficult to control in the spring. “Better growing conditions mean increased weed growth,” notes Pawlak.

Plan your program to control weeds for the duration
In Iowa, with resilient weeds like waterhemp, preemergence herbicides with a long residual, such as Valor and Fierce, are essential for weed management. Pawlak says there’s also been increased frequency of common lambsquarters and velvetleaf over the past two years due to favorable growing conditions for those two weed species. So making applications before the soybean crop emerges is now more important than ever, as these species are more difficult to control postemergence.

“Preemergence residual herbicides are the only way for growers to get their fields off to a healthy and productive start,” he adds. “Full labeled use rates of multi-effective modes of action are most important for soybean growers to keep in mind this spring.”

In the long run, with timely spring applications, preemergence residual herbicides help increase soybean yields by reducing weed competition and introducing greater flexibility in post-application timing. “All weeds are easiest to control while they are still in the soil during germination and prior to emergence,” Pawlak notes. “Postemergence options are getting fewer and fewer with the increase in herbicide resistance. It’s more important now than ever to have a strong residual program.”

Rely on more than postemergence herbicides
Joe Wilkens grows corn and soybeans on 1,250 acres at Nauvoo, Ill. He’s had trouble in recent years killing weeds in Roundup beans, specifically waterhemp. Wilkens turned to Valor, Valor XLT and Fierce herbicides for help and has noticed a dramatic decrease in weed pressure with no carryover concerns.

“We have pretty good tools to grow really whatever bean we want to grow,” he says. “We use Valor or Fierce as our base herbicide and then don’t have to be concerned with being on time with our postemergence application.”

Pair cultural practices with chemical applications
In addition to being timely with your pre-applications, Pawlak recommends farmers plant cover crops for both weed management and better soil health. “Cover crops give growers enriched nutrients, improved soil tilth and less erosion,” he says. “Valor is not only cover crop friendly, but it also provides excellent rotational flexibility.”

Another spring planting best practice, especially where you have resistant weeds, is to plant narrow-row beans. “This allows for a shorter timeframe between planting and crop canopy; therefore the herbicide doesn’t need to last quite as long,” says Pawlak.