Agronomy Note from Chris Kallal Territory Agronomist Asgrow/Dekalb ...
Agronomy Note from Chris Kallal Territory Agronomist Asgrow/Dekalb Seed Sherman, IL Guys, Over the past week or so, I have started to notice quite a bit of crown rot in fields. Typical places to find it right now are the fields that have senesced a great deal over the course of the last 7-14 days. Plants with a compromised root system will die rapidly with additional stresses, such as the heat we just experienced. Plants can go from green and healthy with no apparent issues to completely dead with a dropped over ear in a matter of days. Here are some observations that I’ve made so far: 1. I have found it in DEKALB, Pioneer, Wyffels, Channel, AgVenture, and Burrus. No single company or genetic family seems to have it any worse than others. I have identified it in 5 different DK genetics and 3 different PIO genetics so far. There very well could be a genetic component to this, just like there is with most disease, but I don’t think anyone rates for this. There are probably different levels of tolerance, but no resistance. I really haven’t identified any trends yet. 2. I have found it in 1st year corn as well as multiple year corn. It is a function of stress more than rotation but since corn on corn more often experiences stress I would expect to see it more regularly corn on corn. 3. To date fields in NW Christian County, across the majority of Sangamon County, Eastern Morgan County, and Northern Greene County have been identified having the issue. I suspect it is more widespread than that, but that is the area we’ve seen it in so far. Areas that were dry through much of July and August will have it the worst. Stress during grain fill is the opportunity these pathogens need. 4. To date, I have predominantly been looking at some of the earliest planted corn. April 11th to 20th. Generally the problem becomes visible around Mid R5. The earlier planted and earlier maturity hybrids will reach that point first so it stands to reason you will see it there first. Maturity and planting date also impact the growth stage plants are at when they encounter environmental stress – this can impact the infection and development of disease. 5. The crown rot set in early enough that now the stalk integrity is totally compromised. It is pretty easy to collapse the stalk 2-4 nodes above the soil. Several of the plants fall over as you walk through the field. 6. In several cases, the corn with stalk rot hasn’t even black layered yet. When the plant (and ear) dies prematurely you will get an artificial black layer and the grain will still dry down. Kernels will be smaller and shallow and the cob is often soft. The closer it was to black layer when it died the more normal the ear will be. 7. The crown rot shut off the ability to translocate any water/nutrients from the roots to the above ground portion of the plant. So in an effort to finish filling the ear, it is totally cannibalizing itself.
8. At this point, I would expect the yield impact to be fairly minimal. I would say it set in close enough to black layer that we didn’t miss much grain fill. Most of the ears on the plants in question are still impressive. 9. The potential for yield loss going forward due to down corn is far greater than what we may have lost in grain fill. 10. In some cases, the cob is getting soft already too due to a premature death. 11. In a couple of fields I’ve been in, the majority of the plants are solid green from the ear up. And then you will find random dead plants infected with crown rot. This is very common. These plants were under more stress during grain fill or were just the unlucky ones. I call these “ghosted” plants. They go from green to dead quickly and just “give up the ghost”. Each day that passes there will be a few more dead plants. 12. I have dug some pretty healthy looking plants adjacent to those that are dead, and the healthier looking plants have some crown rot setting it. I expect it’s a matter of time before these plants look like their neighbors. 13. The infection probably happened back in April or May when the plant was small, much like how SDS does. Cool, wet weather when plants are small are ideal for infection. Fusarium is the probable cause. The infection is not the issue as much as stress during grain fill. Every plant is probably infected every year to a certain extent. These pathogens are very common. Having stress during grain fill is what really creates the opportunity. This is not really a rare or unique issue but the severity does vary from year to year. High populations, good pollination and large ears and high yield potential set us up to have issues if the right environmental conditions and stresses occurred. 14. Crown Rot can also be referred to as Fusarium Root Rot or Fusarium Stalk Rot. And in most cases, Fusarium is not the only stalk rot in these plants. It is highly likely that Anthracnose, Diplodia, Gibberella, or Charcoal Rot will accompany the crown rot.
So, what do we do from here? 1. I’d suggest digging some plants in fields, and split the stalk down through the crown. 2. If you are not in your fields you have no way to know how good or bad your stalks are. If there is a problem it becomes apparent very quickly when you walk across the rows. This is not something to hide from or be ashamed of. It has far more to do with weather conditions than it does genetics. 3. Problematic fields need to be harvested early to help reduce any harvest losses from down corn. (a few of these recent storms have caused some pretty bad down corn already) I hear a lot of growers saying they want to “wait to harvest” this year because they don’t want to harvest high moisture corn. That could prove to be a costly mistake. 4. Rotating to beans for 2015 would eliminate the risk for 2015 in that specific field. But since it’s been identified in 1st year corn fields, I’m not sure to what extent that would help. Crop rotation and hybrid rotation (if you are corn on corn) are always a good thing but will not eliminate the pathogens or impact the weather conditions that are the primary cause of the problem.
8. At this point, I would expect the yield impact to be fairly minimal. I would say it set in close enough to black layer that we didn’t miss much grain fill. Most of the ears on the plants in question are still impressive. 9. The potential for yield loss going forward due to down corn is far greater than what we may have lost in grain fill. 10. In some cases, the cob is getting soft already too due to a premature death. 11. In a couple of fields I’ve been in, the majority of the plants are solid green from the ear up. And then you will find random dead plants infected with crown rot. This is very common. These plants were under more stress during grain fill or were just the unlucky ones. I call these “ghosted” plants. They go from green to dead quickly and just “give up the ghost”. Each day that passes there will be a few more dead plants. 12. I have dug some pretty healthy looking plants adjacent to those that are dead, and the healthier looking plants have some crown rot setting it. I expect it’s a matter of time before these plants look like their neighbors. 13. The infection probably happened back in April or May when the plant was small, much like how SDS does. Cool, wet weather when plants are small are ideal for infection. Fusarium is the probable cause. The infection is not the issue as much as stress during grain fill. Every plant is probably infected every year to a certain extent. These pathogens are very common. Having stress during grain fill is what really creates the opportunity. This is not really a rare or unique issue but the severity does vary from year to year. High populations, good pollination and large ears and high yield potential set us up to have issues if the right environmental conditions and stresses occurred. 14. Crown Rot can also be referred to as Fusarium Root Rot or Fusarium Stalk Rot. And in most cases, Fusarium is not the only stalk rot in these plants. It is highly likely that Anthracnose, Diplodia, Gibberella, or Charcoal Rot will accompany the crown rot.
So, what do we do from here? 1. I’d suggest digging some plants in fields, and split the stalk down through the crown. 2. If you are not in your fields you have no way to know how good or bad your stalks are. If there is a problem it becomes apparent very quickly when you walk across the rows. This is not something to hide from or be ashamed of. It has far more to do with weather conditions than it does genetics. 3. Problematic fields need to be harvested early to help reduce any harvest losses from down corn. (a few of these recent storms have caused some pretty bad down corn already) I hear a lot of growers saying they want to “wait to harvest” this year because they don’t want to harvest high moisture corn. That could prove to be a costly mistake. 4. Rotating to beans for 2015 would eliminate the risk for 2015 in that specific field. But since it’s been identified in 1st year corn fields, I’m not sure to what extent that would help. Crop rotation and hybrid rotation (if you are corn on corn) are always a good thing but will not eliminate the pathogens or impact the weather conditions that are the primary cause of the problem.
