Corn stalk rot survey in northwest Minnesota in 2021

This article was written by Angie Peltier, Bruce Potter, Eric Burkness and Bill Hutchison.

Purpose of Study

During a fall survey of 43 corn fields in Becker, Beltrami, Clay, Kittson, Mahnomen, Marshall, Norman, Pennington, Polk, Red Lake and Roseau counties in NW MN for European corn borer, personnel also assessed stalk strength using a “standard” push-test. Briefly, 20 random plants in each field were pushed at ear height more than 30 degrees from vertical. Plants ’failed’ this test by permanently bending or breaking and not returning upright, indicating poor stalk strength.

This survey was not designed to differentiate between stalk quality issues caused by disease or other stressors but rather to assess standability of the 2021 corn crop.

Results

Developing corn kernels place a high demand on the plant for sugars. Stress slows photosynthesis, reducing the amount of sugar the plant can produce. Different stresses can reduce the rate of photosynthesis: too much or too little moisture, nutrient imbalances, plant injury (ex.: hail, insects, diseases), excessive plant populations, and even long-periods of cloudy weather.

Hybrid genetics and/or high yield potential combined with stress during grain fill can increase the probability of stalk quality issues. Stalk quality tends to decrease the longer the crop remains in the field unharvested.

If a plant is unable to keep up with kernel sugar demand, it can rob sugars from stalk tissue, deteriorating stalk integrity and predisposing it to stalk rotting fungi. 

In NW MN, the percentage of plants suffering from stalk rot ranged from a low of 0 percent (14 fields) to a high of 75 percent (1 field; Figures 1 and 2); 51% of the fields had stalk quality issues that might have impacted harvestability, more than the 46% of fields in 2020. 

Figure 1. The percentage of plants failing the push test. 

 

Figure 2. The location of fields surveyed and the percentage of plants failing the push test in 43 fields in 2021.

Crop stressors in 2021 included the historic drought throughout much of the region, with between 8 and 14 inches less precipitation than normal between Sep 1, 2020 and Aug 30, 2021. Those areas that received some rain had more kernels and so required more sugars, some of which was likely to be redistributed from and weaken stalks. Without adequate soil moisture, plants also struggled to take up sufficient nutrients or as efficiently photosynthesize and produce and accumulate the sugars needed for grain-fill with rolled leaves. 

This survey was sponsored by check-off dollars through the Minnesota Corn Research & Promotion Council.