Grain Observations


This post shares observations of what I’ve been seeing in fields pre-harvest and during harvest during this 2018 growing season. Some of these problems stemmed from hail/wind damage and others insect damage. This is a longer post with the desire to have many resources available to you in one place. Hopefully this will be helpful for diagnosing concerns as harvest continues.

Soybean Observations

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(Photos above) Hail-damaged soybeans pre-harvest. The plants in this field weren’t pummeled into the ground, but from the road it was deceiving as to what the soybeans were actually like on these plants. The two smaller photos are all the soybeans found on 2 adjacent plants from the top soybean photo pre-harvest. There were a lot of aborted pods on stems and moldy beans in general. For those who combined hail damaged beans in the area, farmers shared they had everything from ‘lima’ beans to shriveled, moldy beans as you can see in these pics, which is also what we were anticipating may be found.

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Examples of soybeans that had sprouted in the pod pre-harvest. We may unfortunately see a lot more of this with additional rains.

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Removed a bunch of pods from a plant with Diaporthe/Phomopsis complex in which there were many flat, unfilled pods and pods of various stages of fill. This is what I found in the pods. This complex consists of diseases such as Pod and Stem Blight, Stem Canker, and Phomopsis Seed Decay. Perhaps note which varieties you notice more of this.

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Two different grain quality concerns in soybean. (Left photo) This soybean damage can be attributed to potentially a few things. I have found pycnidia of Phomopsis (Phomopsis seed decay) in samples like this. The UNL Plant and Pest Diagnostic Clinic has also diagnosed Phomopsis Seed Decay in samples. There’s also a publication from Ohio State (https://agcrops.osu.edu/newsletter/corn-newsletter/2017-24/stink-bugs-soybean) which attributes these symptoms to stink bugs. There was stink bug pressure in some fields this past year. So there’s potential that we have a few things occurring creating these symptoms. (Right photo) This soybean damage is called ‘Purple Seed Stain’ and is caused by the fungus Cercospora kikuchii. I mentioned this in this blog post.

Corn Observations

 

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Pre-harvest was seeing quite a bit of Fusarium in places where hail stones or insect damage occurred on ears such as this photo. Notice at the base of the ear, the ‘starburst’ shape occurring within kernels (I think of it like fireworks exploding when viewing the top of the kernel). Kernels infected with Fusarium will have a white/pink fungal growth that later causes kernels to become brown or gray and shriveled.

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This ear was from the same hail-damaged field as photo above and I picked this right before the field was harvested. The Fusarium and picnic beetles had greatly destroyed affected kernels. Cladosporium (green colored fungus) can also be seen affecting this ear where damage had occurred.

Cladosporium ear and kernel rot seen on kernels already affected by Fusarium, particularly in hail damaged fields. This is a lesser ear rot fungi and doesn’t produce a mycotoxin but can create increased damage to kernels. Was recommending taking grain damaged to this extent directly to the elevator.

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The deep red color on this hail damaged ear is due to Gibberella. We may see an increase in this with all this late-season rain. Other symptoms include matted fungal growth with husks sticking to ears. Gibberella has the potential to produce the mycotoxin zearalenone. The presence of the fungus DOES NOT automatically mean the presence of a mycotoxin.

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Kernels at harvest displaying damage from Fusarium and Gibberella. I received a number of samples from various farmers displaying these symptoms and picked out these kernels to show. Notice the pink/red discoloration of the kernel and also the shrunken, damaged kernels that are brown or gray in color. Grain should be dried as quickly as possible to 15% moisture to cease fungal growth in storage.

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This is another field I’ve been watching that was hail damaged. The ears themselves show very little damage; however, my concern is the ‘starburst’ pattern occurring throughout these ears throughout the field. The ‘starburst’ pattern is also characterized by the white lines observed on the sides of individual kernels. This is caused by Fusarium.

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The above photo is that same field at harvest. ‘Starburst’ pattern on kernels seen as white streaking due to Fusarium. More severely infected kernels are brown in color and dissecting them show they were trying to germinate. Also noticing cob rot occurring. Drying the grain to 15% moisture as quickly as possible will cease fungal growth. Fusarium also has the potential to produce the mycotoxins Fumonisin and Deoxynivalenol (also known as DON or Vomitoxin). NOTE: The presence of the fungus DOES NOT automatically mean the presence of a mycotoxin.

Photos above shared by a Clay County farmer who observed kernel germination and Fusarium growth (mostly due to western bean cutworm damage) upon harvesting his field. Hormonal balance within the kernels shifts towards harvest. At full maturity, very little abscisic acid (ABA) is left in the kernel (in both corn and soybeans) which allows them to germinate in correct conditions after harvest. These conditions include moisture and temperatures above 50ºF. Presence of fungi such as Fusarium and Gibberella also increases gibberellins in the kernels allowing for kernel germination with presence of moisture as we’re seeing this harvest. Increasing air flow during harvest will hopefully blow most of these damaged kernels out the back of the combine.

Grain Storage

There’s over 25 species of fungi that can produce ear molds with the majority of them ceasing growth at 15% moisture within the kernel. Thus, we recommend drying grain to 15% moisture as quickly as possible to cease additional fungal growth within the grain bin. The table below shares the days required to dry corn to 15% moisture with 1.0 cfm/bu and various temperature and humidity conditions.

Days required to dry corn to 15 percent moisture with 1.0 cfm per bu. UNL EC

“Since drying time is directly proportional to the airflow, the producer can calculate the estimated drying times when using airflows other than 1.0 cubic foot of air per minute per bushel (cfm/bu). For example: Table II shows when drying corn from 18 percent to 15 percent moisture with 50F and 50% relative humidity air, the estimated drying time is 12.5 days using a 1.0 cfm/bu airflow. If the airflow is 1.25 cfm/bu, the estimated drying time would be 12.5 days / 1.25 = 10 days. For 1.5 cfm/bu, the drying time would be 12.5 days / 1.5 = 8.3 days. For 0.8 cfm/bu, the drying time would be 12.5 days / 0.8 = 15.6 days.” Source: Management of in-bin natural air grain drying systems to minimize energy cost.

Mycotoxin Information

In 2018, we’re primarily seeing Fusarium and Gibberella species which have the potential to produce mycotoxins. Thus, the information below is directed at those fungal species and mycotoxin levels that can be associated with them. Again, the presence of fungi does not automatically mean a mycotoxin is present.

Fusarium sp. mycotoxins.PNG

The following toxins can be produced from species of Fusarium and Gibberella. Source: Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health, Iowa State publication, 1997.

Table 2 expected detrimental feed concentrations of common fusarium mycotoxins-ISU

Source: Corn Ear Rots, Storage Molds, Mycotoxins, and Animal Health, Iowa State publication, 1997.

 

Also, there’s a new app called “Mycotoxins” and it’s another resource with ear rot pictures and mycotoxin information put out by several Universities produced for both Apple and Android devices.

About jenreesources

I'm the Crops and Water Extension Educator for York and Seward counties in Nebraska with a focus in irrigated crop production and plant pathology.

Posted on October 8, 2018, in Crop Updates, Diseases, Storm Damage and tagged , , , , . Bookmark the permalink. Leave a comment.

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