“Trust me, the way we’ve been using Ignite in cotton and soybeans, going after large escaped pigweed, we’re asking for the development of resistance.

Scott recommends that producers avoid using Prefix (Dual plus fomesafen) pre-emergence in soybeans (because of maximum use restrictions). “Fomesafen is probably the best pigweed product I’ve looked at. In order for it to be effective on pigweeds, we need to be at the full pint to 1.25 pint rate.

“If you use your Prefix upfront and you don’t get a rain, we don’t have anything to come back with except Cobra or Blazer, and you’re going to have to be extremely early to get effective control.

“You can use other pre-emergence products like Dual, Authority MTZ, or the Valor-containing products. They’re almost as good as Prefix with a rain and in some cases can be equal. So we want to save fomesafen for our postemergence application.”

Scott recommends that growers target a 2-inch pigweed for a fomesafen (Flexstar) application. “Based on the growth rate of the weed and the growers’ ability to get across acres, it’s a good idea to start spraying when pigweeds are 1-inch tall. A day later, it could be 3 inches tall. It may be too big for Flexstar. It may be too big for Ignite in LibertyLink beans. If we use a residual, we can buy ourselves more time. You may not have to get out there as fast.”

A change in cultural practices can also help in pigweed control, according to Scott. “If you’re growing soybeans on wide rows and you know you have a resistant pigweed problem, you’re setting yourself up for a rough summer, especially in Roundup Ready and conventional soybeans. You’re leaving a lot of space out there for pigweeds to grow in, and the use of at least two residuals is in order, one early and another shot, postemergence, to fill the gap until you can get soybeans to canopy closure.”

Other cultural practices to help in pigweed control include crop rotation, water management to activate preplant or pre-emergence herbicides and seeding rates and methods.

Scott says soybean producers should not wait to find out if a pigweed is resistant. “At that point, you’re too late. You need to be proactive. Identify problem areas, get a residual out upfront, get that first early post application on the books in a timely manner.

“If you continue to stay in the Roundup Ready system, you don’t want to find out after the first glyphosate application that you have resistance. At that point, we don’t have a lot of recommendations. Unfortunately, that’s where we were on a lot of farms in 2009-10.”