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Our Stalk Rot Situation: Update and Best Management Practices

We’ve had all sorts of challenges this growing season, what’s one more? Conditions were right this year for more extensive development of stalk rots in corn. So, what does that mean for us yet this fall? We know how busy you all are, so we are going to keep this short and sweet. This blog will cover some of the more common stalk rots, what kinds we are seeing, what yield impact we can expect, and what we can do yet this year to manage.


Impacts of Stalk Rots

Stalk rots are not uncommon. In fact, most years we see some level of stalk rots that usually cause about a 5% reduction in yield. This year however we are seeing a much higher prevalence, with a few fields as high as 50% damaged stalks. Stalk rots can cause yield impacts both directly and indirectly. If a plant contracts a stalk disease early enough in the growing season, the stalk is unable to convey carbohydrates throughout the plant and to the ear as well as it should, resulting in a lighter weight or poorly filled ear. Additionally, corn will often move carbohydrates stored in the stalk to the ear for a final push on grain fill at the end of the season. If the stalk is rotten, that reallocation of carbohydrates can’t happen, and yield is reduced. Indirectly, yield is reduced from stalk breakage, ear drop, and lodging. These harvest losses also impact our harvestable yield dramatically.

Do we know how much impact stalk diseases had on grain fill this fall? That is going to be very difficult to quantify unless we have fairly precise information about when the disease first showed up and how severe it was. Often to get a better gauge at severity, we look at how early the diseased plants died before the rest of the field. At this point in the growing season, we can no longer make that comparison.


Conditions for Stalk Rot

Several conditions can make stalk rots more prevalent. Higher yielding hybrids with larger ears tend to have more stalk rots. The issue is compounding as the heavy ears also put additional stress on the plant that can lead to breakage and lodging. Additionally, stalk rots are going to be higher in fields that were corn on corn and no-till. There is more inoculum present in these residues and soil, which makes infection more likely. One of the most notable conditions that can lead to stalk rots is something we had in spades this spring: planting into wet conditions in the spring. Our wet spring is still taking its toll. Overall, any form of stress during the season can lead to plant infection and a compromised stalk.


Common Stalk Rots

Some of the most common disease include Fusarium stalk rot, favored by warm, wet conditions. Anthracnose and Diplodia both like warm, wet conditions as well. Gibberella prefers wet, cool weather. While each of these diseases have notable distinguishing features, we really aren’t going to go into those details here. Why? At this point in the growing season, its likely that your corn plants have multiple of these diseases, making it impossible to tell them apart. And also, at this point, it doesn’t really matter which one(s) you have. Because our management strategy is the same here on out.


Management

Management for this fall: SCOUT YOUR FIELDS. It’s important to check each field and prioritize those with stalk rots above any else. An article from Pioneer suggests this is even more critical than prioritizing based on moisture. An article from the University of Nebraska seconds that statement and also suggests that it will likely be more economical to harvest grain wet and then dry that grain down than have to deal with harvest losses from lodging and ear drop.



There are two main ways to check stalks when you are out in the field. The first is the push test. Take an individual stalk, grab it at ear level, and lean it 30 degrees away from vertical. If the plant doesn’t return to vertical or breaks off, that stalk has been compromised. The second test is a pinch test. Down at the bottom of the stalk, pinch between two nodes. (Make sure you are above the brace roots.) If you can crush the stalk fairly easy, stalk rot has reduced its structural integrity. It doesn’t matter which method you choose, but be sure to try it at multiple locations in the field. Some sources suggest 100 plants randomly across the field. Others suggest 20 plants at three locations. The important thing is to try and get a representative sample. Any field with more than 5-10% damaged stalks should be on your priority list.



That is all we can do this year. Simply prioritize harvest. You can make some plans for next year though.


· Potassium is very important for stalk strength, so be sure to check your fertility levels for adequate K. Now is a great time to get on our soil sampling list to get your acres sampled yet this fall. Getting your fertility right will help dramatically with plant health and yield. Get in contact with the guys to find out what services we offer.


· Pioneer provides ratings for stalk strength for all their hybrids. Be sure to pick out a hybrid that ranks well, particularly if you are putting it on some corn on corn acres.


· Any sort of crop stress will lead to increased stalk rots. This includes insect pressure, but also foliar diseases. While fungicides are not labeled for any stalk diseases, by reducing the infection of leaf diseases, we are able to keep the plant healthier as well as preserve more green leaf area for photosynthesis, both which will help reduce the chance and impact of infection.


Those are just a few things to look at moving towards next growing season. Take a few minutes some morning this week and head to the fields to check your stalk integrity. You’ll be glad you did when the fall and winter winds come along. Questions about disease in one of your fields? Ask in the questions below, or get in contact with one of the guys.


Resources

https://fyi.extension.wisc.edu/fieldcroppathology/2014/09/10/disease-considerations-for-soybean-and-corn-harvest/

https://cropwatch.unl.edu/stalk-rot-diseases-creating-harvest-problems-corn-unl-cropwatch-oct-30-2012

https://www.pioneer.com/us/agronomy/managing_stalk_rot.html

https://www.extension.purdue.edu/extmedia/BP/BP-89-W.pdf

http://extensionpublications.unl.edu/assets/pdf/ec1898.pdf

https://www.wyffels.com/agronomic-solutions/corn-disease-management/stalk-rot-diseases

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