Just a reminder that stalk rots in corn may be an issue this fall, especially if fields experienced severe hail damage or were flooded for extended periods this year.

Stalk rots can weaken the structural integrity of the plant, causing them to lodge, break or collapse, making harvest quite difficult. Yield loss can occur if ears are dropped or cannot be retrieved when plants are picked up off the ground during harvest. Hybrids that sustained crop stress, insect damage, flooding or hail damage may be prone to stalk rots.

Some of the more common stalk rots we see leading up to harvest in Nebraska include Fusarium stalk rot, Gibberella stalk rot, Anthracnose stalk rot, and Charcoal rot.

To assess if stalk rots could be an issue in your field, conduct the “pinch test” or the “push test” on at least 100 plants. For the pinch test, pinch one of the lowest internodes of the stalk and see if it crushes between your thumb and index finger. For the push test, push the top third of the plant away from you (about 30 degrees from vertical) and see if it snaps back or leans over. If the plant doesn’t snap back, you may have a stalk rot.

The best way to know if your field has been compromised with stalk rots is to submit a sample to the Plant and Pest Diagnostic Clinic in Lincoln for accurate diagnosis. If you believe that stalk rots are an issue in your field, prioritize those fields during harvest. Strong fall winds could wreak havoc on those fields when it comes time to harvest, so plan accordingly in advance.

Other harvest concerns

One of the most common weeds we have problems with at harvest is Palmer amaranth.

Palmer amaranth has a long emergence period and plenty of fields have high weed pressure this time of year, especially on field borders. Depending on the time of plant emergence, one Palmer amaranth plant has the capability to produce more than a million seeds. Research has shown that 99% of Palmer amaranth seeds that run through the combine will survive. Thanks to mechanical harvest, these seeds will be blown out the back of the combine and moved further into the field. Seeds can also spread from field-to-field via harvest equipment.

Several producers have opted to harvest around thick patches of Palmer amaranth to avoid seed dispersal. To help reduce weed pressure next spring, they can disk or shred these weed patches after harvest and plant a cover crop that has plenty of biomass (i.e. cereal rye or bin-run wheat) to keep soils cool and reduce weed seed germination.

While disking and planting a cover crop can be beneficial in managing weeds, be mindful about disking. Research has shown that burying Palmer amaranth seeds three to four inches deep for three or more years helps reduce seedling germination. However, you should avoid disking every year as this will only redeposit Palmer amaranth and other weed seed on the soil surface.

Therefore, if you choose to disk, do it once every three to five years. Cover crops may also be more desirable for no-till operations compared to disking. The use of cover crops has become popular for weed management after harvest but make sure to plant early enough to obtain good cover crop growth and biomass accumulation. This helps reduce light penetration and weed seedling germination next spring.

Sarah Sivits is the Dawson County Extension educator in crops and water, and serves Dawson, Buffalo and Hall counties. Contact her at (308) 324-5501 or by email at ssivits@unl.edu.

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