Just Like Soybean Farmers, Weeds Are Good at Adapting to Wild Weather

Of the many variables involved in row crop production, few impact a farmer’s bottom line more than two that reign supreme in unpredictability: weather and markets. And while good signs are pointing to future market conditions, seasonal weather changes are upon us and winter has arrived.

Earlier in the year, headlines were flush with news of El Nino and La Nina patterns and a transition from one to the other that anticipated weather extremes and fluctuations; however, much of the country experienced a relatively mild fall.

But like farmers themselves, the weeds that often evade them are also good at adapting to changes.

As Jack Frost settles in, those slumbering foes – pigweeds and others that are problematic for soybeans – lie dormant beneath frozen ground and frost-covered fields, waiting to choke out crops and rob yields come spring.

Where weed management is concerned, Dallas Peterson, weed scientist at Kansas State University, says it’s tough to know what spring will be like, but a watchful eye can help to anticipate how weather will impact emergence and control.

“Cooler, wetter weather can delay germination of warm-season weeds like pigweeds,” says Peterson. “But if it warms up earlier than expected, then we’ll see earlier germination that influences what you may see through spring and as farmers approach planting.”

A sequential program of residual herbicide applications helps with weather insurance, he says.

“Get the first application down before pigweeds emerge. With that application in place, it can be activated by subsequent rains and control early germinating pigweeds.  Sequential residual applications at planting or early post-emergence will then help to extend pigweed control later into the season.”

Once spring arrives, it’s important to scout fields early for the presence of winter annual weeds and early emerging spring weeds.

“We have to scout throughout the season and plan, keeping an eye on the weather,” Peterson suggests. He also adds that using a residual program helps tremendously to thin populations and offers more leeway with timing for post-emergence applications.

“When we don’t get an activating rainfall when we need it, or when we receive too much rain and dilute residual herbicides, then it’s important to target emerged weeds that escaped residual control early, before they get too big,” Peterson says. “It’s easy to lose control of emerged weeds quickly as the weather warms and they start growing rapidly.”

Simply waiting until late spring to determine a weed management plan and course of action exposes farmers to the possibility of less effective weed management and missed opportunities for control.

“Sequential applications with overlapping residuals gives the best chance of good weed control,” Peterson concludes. “Manage the seed bank and target the weeds based on field history, before you think they’ll germinate and emerge, then follow up with your second application in a timely manner. We have to catch new species early on to have a major impact. Timing is essential. You’ll be more successful than if you wait to see what comes up, and then decide.”