The Environmental Protection Agency (EPA) moved up the cutoff dates for over-the-top application of dicamba label products for soybeans – to June 12 for Illinois, Indiana and Iowa and to June 20 for South Dakota. Those with the new June 12 cutoff also face a growth stage application cutoff of V4. 

While the timing of the announcement was not ideal given most farmers had already locked in their seed and chemical purchases, the move wasn’t a complete surprise.  

“Farmers were hoping it wouldn’t happen, but they weren’t necessarily surprised about it,” explains AgriGold Agronomist Brian Ternus, who points out Minnesota changed its cutoff to June 12 last year and that led to a big drop in complaints. Ternus predicts the earlier cutoff for South Dakota will affect a few farmers. 

AgriGold Agronomist Kevin Gale out of Illinois expressed similar sentiment: “It would’ve been nice to have that notice earlier in the sales year so farmers could plan accordingly. But the sector has also been gearing up for the transition the past year or two with a quick transition to XtendFlex® technology that allows us to utilize other herbicide programs like Liberty® herbicide to control late-emerging weeds.” 

New label fits with efforts to kill weeds early

“We’ve been talking ‘start clean, stay clean’ for years,” Gale says, noting farmers have tended to err on the earlier side with dicamba products, using them as a burndown or early post-application. “Our whole goal is trying to get weeds under control at 4 inches or smaller to maximize the effectiveness of that herbicide. Allowing weeds to grow beyond that results in more potential for resistance and inadequate control.” 

If soybeans are planted in a timely manner, the deadlines should roughly coincide with when farmers would otherwise aim to have those applications completed – when soybeans have some growth and canopy closure, but before flowering. 

Another major timing consideration is farmers using a preemergence herbicide should aim for a post-application that ideally includes another residual product in the tank mix 21 to 30 days later, according to Gale. 

But the larger concern for many farmers is the implications of a delayed planting season.

Have a Plan B for when the weather doesn’t cooperate

“The earlier deadline narrows the application window by 10 days for South Dakota farmers. If conditions cooperate, the June 20 deadline should be an achievable timeline for application,” Ternus says. “But if you get too much rain or too much wind, those 10 days become significant. 

“As long as farmers are planted mid-May or within a few days of that, most should be able to spray by June 20,” Ternus details. Gale also signaled late-May planting would be problematic for farmers with June 12 cutoffs. 

Ternus says farmers locked into dicamba for their spray selection need to do all they can to get it sprayed before the deadline, noting dicamba as a post-planting spray offers some soil activity control and can help control seedlings that haven’t emerged.

“If you get past the deadline, you may need to consider alternative herbicides to control weeds like waterhemp that you were counting on dicamba to control,” Ternus continues. “Products like Liberty® herbicide (glufosinate) can also be sprayed after the June 20 deadline and can help control some of the weeds that have started escaping Roundup® herbicide.”

Using multiple modes of action and overlapping residuals is also important, both for navigating the new dicamba cutoff dates and for a successful weed control strategy in general, Gale emphasizes. 

Ternus adds these dicamba application reminders: “Pay attention to temperature and make sure they are under 85 degrees Fahrenheit. Watch which way the wind is blowing relative to sensitive crops and residential areas. And keep the V4 cutoff in mind, too.” 

Will ongoing changes impact seed choices? 

Ternus expects farmers in South Dakota to continue to evaluate their operations’ reasoning for choosing dicamba-tolerant soybeans, based on our evolving regulator environment and notes decisions made by the EPA could have some impact on seed choices. 

“Some farmers plant dicamba-tolerant soybeans because they don’t want their soybeans to get cupped when their neighbors spray dicamba. Others may think a bit harder about whether they’ll be able to plant in time and whether they have the capacity to get everything sprayed before the new deadlines,” Ternus says. 

“If farmers are concerned EPA is going to come out fairly late like they did again this year, they may either hold off or go with chemistry they think is unlikely to face regulatory changes,” Ternus continues. 

For help weighing your soybean seed and weed control options on your farm, reach out to your local AgriGold agronomist.