Which weed troubles your farmers’ the most? The answer should be any weed taller than two to four inches. Beyond this height, controlling a variety of species becomes difficult, and in soybeans, postemergence options are limited.

The limited postemerge options is why using a pre-emergence weed control product, and specifically one that has residual activity to enhance the performance of post applications by keeping weeds smaller and easier to control, is so important, according to Dow AgroSciences.

Every inch of weed growth counts against yield. Early weed competition robs developing soybean plants of sun, water and nutrients. Southern Illinois University research shows six to eight inches of dense weed growth can cause four to five bushels per acre of lost yield—and profit.

Considering today’s market prices, ag retailers and crop consultants should strongly encourage and motivate soybean growers to protect their soybean fields and yield potential. Although you would think that soybean growers are motivated to change their weed control program, they often seem hesitant to change, especially if a weed-control measure costs a little more than they’ve been paying.

“Even with increased demand and good soybean markets, less than 50 percent of soybean fields currently receive a pre-emergence herbicide,” according to Dow AgroSciences. “Many fields could still benefit from the added protection against tough and resistant weeds that are continuing to spread.”

Dow AgroSciences is promoting its Sonic herbicide that is a pre-emergence herbicide that also delivers residual activity. The company quotes Nick Saathoff of Heritage FS in Bourbonnais, Ill., who says applying a residual herbicide provides a valuable window of time to manage workloads, attend to other activities or wait out the weather. He said a preplant application allows “45 days before we have to worry about going in for a spray of glyphosate” and the weeds are smaller when post sprayed and much easier to control.

There is no doubt today that a two-pass weed control program is better to stop difficult-to-control and herbicide resistant weeds than a glyphosate-only program. But it is the ag retailer and crop consultants job to convince more farmers.