So Your Crop Emerged Before It Got a Herbicide

May 10, 2024

By Meaghan Anderson

With the quick planting that happened the week of April 22-26 and the lack of field activity since due to high winds and rain, some fields may have crops emerging that have had no preemergence herbicide. While some herbicides can be applied prior to or after crop emergence, many have restrictions related to applications when crops have emerged. This could mean applicators need to change carrier, adjuvants, or herbicide to avoid crop injury. Consider the following prior to spraying any fields that were planted ahead of the rains.

Scout every field prior to spraying

Growing degree days (GDDs) have accumulated relatively quickly, but there is always variability in crop development from one field to another. Since Wednesday, April 24, GDD accumulation is very near or past the approximate 90-120 GDDs required for corn emergence. Soybeans generally require a similar number of GDDs to emerge, but there is typically more plant-to-plant variability across fields. While one field may have no visible emergence, other fields may be further along due to soil type, landscape position, soil moisture, or surface residue. Investigating how close the corn or soybean plants are to emerging is critical to making informed decisions.

Keep in mind that even crops very near emergence can be injured by some preemergence applications. Soybean plants often create a crack in the planted row prior to emergence. Any condition that allows for concentrated herbicide to directly contact plant tissue (like washing into an open furrow) may result in substantial injury.

In addition to checking for crop emergence, look closely to see if small weed seedlings are emerging as well. Agronomists have noted emergence of many common species in fields not yet treated with herbicides, including morningglories, foxtails, woolly cupgrass, ragweeds, velvetleaf, lambsquarter, and waterhemp.

Check herbicide labels for application restrictions related to emerged crops

Applicators need to carefully read herbicide labels to determine if products in the planned preemergence application can be applied near or after emergence.

Most soybean preemergence herbicides, particularly ones containing sulfentrazone, metribuzin, or flumioxazin, have explicit statements on the label regarding preemergence applications. None of these herbicides should be applied to soybeans that are emerging. For example, the Kyber herbicide label notes “severe injury will occur if Kyber is applied when soybeans have begun to crack” and “preemergence application of Kyber must be made within 3 days after planting and prior to soybean emergence.”

Most corn preemergence herbicides allow for more flexibility, though some have restrictions on growth stage, adjuvants, or carrier when the application is made after the crop has emerged. Some corn herbicides, like TriVolt, allow postemergence applications during a short window – spiking to the 2-leaf collar (V2) growth stage. While crop oil concentrates (COC) and methylated seed oils (MSO) may be recommended for certain preemergence herbicide applications to control emerged weeds, these may not be recommended once the crop has emerged due to likelihood of crop injury.

It is common for a portion of corn’s nitrogen needs to come from a UAN carrier with preemergence herbicide applications. Herbicide labels vary in their restrictions related to UAN use as a carrier when applied to emerged corn. While some labels simply recommend against using UAN as a carrier, others explicitly prohibit it. Emerged corn exposed to UAN will experience foliar burn, similar to that of a contact herbicide. You can read more about UAN as a herbicide carrier on emerged corn in this article.

Change your plans

I realize that many farmers have significant fieldwork to complete once soils dry out, but the risk to the crop is significantly less if time is taken scout fields, check herbicide labels, and adjust plans if necessary. These adjustments may mean using alternative herbicides due to risk to the crop, changing the carrier or adjuvant, or even adding a different product to control emerged weeds. Reach out to your local field agronomist if you have questions or need assistance with managing weeds this spring.

Source : iastate.edu

Video: Why Your Food Future Could be Trapped in a Seed Morgue

In a world of PowerPoint overload, Rex Bernardo stands out. No bullet points. No charts. No jargon. Just stories and photographs. At this year’s National Association for Plant Breeding conference on the Big Island of Hawaii, he stood before a room of peers — all experts in the science of seeds — and did something radical: he showed them images. He told them stories. And he asked them to remember not what they saw, but how they felt.

Bernardo, recipient of the 2025 Lifetime Achievement Award, has spent his career searching for the genetic treasures tucked inside what plant breeders call exotic germplasm — ancient, often wild genetic lines that hold secrets to resilience, taste, and traits we've forgotten to value.

But Bernardo didn’t always think this way.

“I worked in private industry for nearly a decade,” he recalls. “I remember one breeder saying, ‘We’re making new hybrids, but they’re basically the same genetics.’ That stuck with me. Where is the new diversity going to come from?”

For Bernardo, part of the answer lies in the world’s gene banks — vast vaults of seed samples collected from every corner of the globe. Yet, he says, many of these vaults have quietly become “seed morgues.” “Something goes in, but it never comes out,” he explains. “We need to start treating these collections like living investments, not museums of dead potential.”

That potential — and the barriers to unlocking it — are deeply personal for Bernardo. He’s wrestled with international policies that prevent access to valuable lines (like North Korean corn) and with the slow, painstaking science of transferring useful traits from wild relatives into elite lines that farmers can actually grow. Sometimes it works. Sometimes it doesn’t. But he’s convinced that success starts not in the lab, but in the way we communicate.

“The fact sheet model isn’t cutting it anymore,” he says. “We hand out a paper about a new variety and think that’s enough. But stories? Plants you can see and touch? That’s what stays with people.”

Bernardo practices what he preaches. At the University of Minnesota, he helped launch a student-led breeding program that’s working to adapt leafy African vegetables for the Twin Cities’ African diaspora. The goal? Culturally relevant crops that mature in Minnesota’s shorter growing season — and can be regrown year after year.

“That’s real impact,” he says. “Helping people grow food that’s meaningful to them, not just what's commercially viable.”

He’s also brewed plant breeding into something more relatable — literally. Coffee and beer have become unexpected tools in his mission to make science accessible. His undergraduate course on coffee, for instance, connects the dots between genetics, geography, and culture. “Everyone drinks coffee,” he says. “It’s a conversation starter. It’s a gateway into plant science.”