Soybean sprouts in Iowa field

(Photo: Iowa Soybean Association)

Scouting, herbicide applications make up for post-planting activities

May 25, 2023 | Kriss Nelson

Iowa farmers have made great strides with most of the state’s soybeans and corn planted, according to the Iowa Crop Progress and Conditions report released by the Iowa Department of Agriculture and Land Stewardship. So now, the focus is shifting to post-planting activities.

Iowa Soybean Association (ISA) research agronomists have been assisting with planting and observing trials, and the overall consensus is that emergence has begun and appears to be without issue.

Drew Clemmensen, ISA research agronomist, says that in southwest Iowa, timely rains helped to get the crop out of the ground, which escaped injury from cool weather after early planting.

ISA research agronomist Scott Nelson has been visiting fields in northwest and northeast Iowa this week and says he has also been seeing good soybean and corn stands.

“Farmers are seeing equal stands; everything has come up at the same time despite that earlier planting date,” says Nelson.

Alex Schaffer, ISA research agronomist, says some producers in northeast Iowa may have to decide to replant after some pockets of rain fell, bringing several inches of rain a few weeks ago, while others are still working on finishing planting.

Making plant stand assessments

Analyzing plant stands can provide insight into planter, genetic performance and potential pest infestations.

ISA research agronomists suggest making stand assessments and keeping notes for success for next year’s growing season. Also, if the emerged population is lower than expected, it could call for replanting.

While making those stand assessments, Nelson advises checking the planting depth.

“I have seen some shallow planting in soybeans, and that is going to reduce yield,” he says. “Checking planting depth will evaluate how well your planter did. Dig around and see if the plants hit their target depth. Take notes for next year.”

Post-emergence herbicide application

As crops emerge, so do weeds, and the time has come to take action with post-planting herbicide applications is now.

“You must stay diligent with your herbicide programs,” says Clemmensen. “Hopefully, the pre-emergence herbicides keep the fields clean, but it is time to get out, check your fields, and be ready with the post-herbicide pass.”

Schaffer says to keep a close eye on those problem areas to avoid an outbreak of noxious weeds such as waterhemp and marestail.

“Those weeds can get out of control in a hurry, and there is a tight window to spray them,” he says. “Keeping weeds in check should be the focus at this point.”

Nelson reminds producers to be aware of the dicamba cut-off date of June 12 or the V4 growth stage of soybeans.

The regulation forcing farmers to make an early herbicide application could be a good thing.

“Those earlier dicamba applications knock weeds down earlier. Otherwise, farmers sometimes allow weeds to get too large,” he says. “Forcing them to get them when they are smaller will allow for better weed kill.”

Scouting for pests

It is also time to be on alert for early-season insects and seedling disease.

Clemmensen emphasizes the need to assess areas where a seed treatment was not applied or where a weaker treatment was used and evaluate wet and weed-infested areas.

As warmer days accumulate, so do the chances for black cutworm and armyworm infestations.

The 2023 Iowa Moth Trapping Network provides a weekly assessment of black cutworm and armyworm moth flights into the state.

“I have seen a little black cutworm activity, which can be devastating,” says Nelson. “Although you can treat, often by the time they do their damage, it’s too late.”

While scouting for pests, Clemmensen says to dig under the soil surface near the plant, as some will stay under the surface to stay out of the day’s heat.

Bean leaf beetles could appear in soybean fields soon as the first cutting of hay is coming off, and they tend to move from those grassy areas to soybeans.

Although too early, Nelson urges producers to be ready to scout for soybean gall midge in the next three to four weeks.