Assess Your Herbicide Program's Success

Careful notes and planning will put you ahead of weeds

That ugly patch of weeds the combine just tore through creates headaches and costs you money. Just one Amaranthus species — waterhemp or Palmer amaranth being the most common — for every 3’ of row can reduce yield by up to 30%, according to experts at the Weed Science Society of America.

The fall is an excellent time to evaluate the success of your herbicide programs. “Treat it like you’re back in school and give your weed control a grade,” suggests Luke Schulte, Ohio field agronomist and herbicide specialist at Beck's Hybrids. “Did you get an A, B, C, D or F?”

Scout your fields to see: What weeds did you miss? What changes should you make going into the next season? Will the weed escapes cause you harvest issues? What will the remaining weeds do to the future weed seedbank?

“Your herbicide management program needs to be evaluated from start to finish,” says Ben Wilson, AGRIntelligence agronomist with Helena. “Ask yourself: What made 2021 unique that I can learn from? Take note of the season’s challenges to see how they tested your management plan.”

In-Field Observations

Throughout the season, Wilson suggests taking digital or handwritten scouting notes. Note the emerging weeds and evaluate the thresholds for treatment needs. Several programs are available now to let you drop geo-reference flags or pins to mark weeds, which can help you track year-over-year infestations.

When evaluating fields, Wilson’s No. 1 observation is around crop canopy. 

“If I have a weed escape, I probably had a crop canopy problem,” he says. “What’s causing that problem? Row spacing? Varietal issue? Seed population? Fertility or soil type issue? Likely there will be something in there that will trigger a management decision.”

Your goal for each season is to avoid rescue herbicide treatments, Wilson says. He says the way to achieve that is to use residual herbicides with multiple sites of action. He says his customers with the most durable programs use a two-pass residual program that consists of a pre-emergence herbicide followed by a post-emergence herbicide. 

Layer on the SOAs for Heavy Weed Pressure

Herbicides with two or three effective sites of action (SOAs) can offer your fields the most protection against troublesome weeds — even those with herbicide resistance.  Research by Beck’s Hybrids shows a 29% increase in waterhemp control when employing two SOAs versus one. Three SOAs increases waterhemp control by 37%. 

Source: Beck’s Hybrids