Knox County Vomitoxin Research Station #4 Installed – Thanks to Dr. Pierce Paul and Crew!
Source: Dr. Pierce Paul, OSU
Wheat is now between Feekes 8 (flag leaf emergence) and Feekes 10 (boot) across the state. Feekes 8 marks the beginning of the period during which we recommend that you begin scouting fields to determine which disease is present and at what level. Septoria tritici leaf spot is usually one of the first to show up, and it has already been reported in some fields. So far, it is restricted to the lower leaves and severity is low in most of the affected fields. This disease is favored by cool (50-68F), rainy conditions, and although it usually develops early in the season, it really does not cause yield loss unless it reaches and damages the flag leaf before grain fill is complete.
Like many other foliar diseases, Septoria reduces grain fill and the size of the grain. It usually does not affect the number of spikelets per spike, an important yield component that is defined very early in the development of the plant. A fungicide application at this time will control Septoria and powdery mildew, another disease that usually shows up early under cool conditions, protect the flag leaf, and minimize grain yield loss. If the weather conditions continue to be rainy and favorable for foliar disease develop, spores will continue to be produced or blown in from other areas, and new infections will occur, particularly if the variety is susceptible.
Results from previous studies have shown that the greatest benefits from foliar fungicide applications were seen when applications were made to a susceptible variety between Feekes 8 and 10. This is largely because most of our major foliar diseases usually develop and reach the flag leaf after Feekes 8-9. However, the residual effects of a Feekes 8-9 fungicide application will not adequately protect the head from late season diseases such as head scab and Stagonospora glume blotch or the flag leaf from rust and Stagonospora leaf blotch. In addition, some of the fungicide that effectively control foliar diseases are ineffective again, or are not recommended for control of, head scab.
There are several very effective fungicides available for use on wheat see the post above or (see resource chart). Carefully read labels before making an application.
On Feb 11, 2021, I gave a talk entitled “Management of Gibberella ear rot and Vomitoxin in Corn with Fungicides: Lessons Learned from Head Scab” as part of the 2021 Virtual Corn and Soybean School. I summarized years of fungicide efficacy research on head scab, a disease of wheat caused by the same fungus (Fusarium graminearum [Gibberella zeae]) that causes Gibberella ear rot (GER) in corn. Head scab and vomitoxin in wheat have been more widely studied than GER and vomitoxin in corn, as a result, a lot more is known about fungicide efficacy against scab/vomitoxin than against GER/vomitoxin. I therefore used lessons learned from head scab research, coupled with data from a limited number of GER fungicide efficacy studies to provide guideline on GER and vomitoxin management in corn. More than 220 people attended the 40-min-long program, asking questions covering various aspects of corn pathology. Below are more complete responses to several of these questions:
Q: How do you explain high vomitoxin levels in grain with no apparent ear rot observed? Can drought stress alone be a culprit?
A: Infection of the ear, development of visual symptoms (ear rot), and contamination of grain with vomitoxin all depend on weather conditions during the weeks after silk emergence. Once the fungus enters the ear via the silks (infection) and begins to colonize the developing grain, it produces vomitoxin, even if subsequent weather conditions are not favorable for mold and ear rot to develop on the outside of the ear. This is particularly true if infections occur late and conditions become relatively dry and unfavorable for visual symptoms to develop.
Q: It looks like the triazoles are doing the work on VOM, more than strobies, is this correct?
A: Pulling from my years of experience with head scab and a limited number of fungicide efficacy studies on Gibberella ear rot and vomitoxin in corn, I would be more inclined to recommend a triazole than a strobilurin fungicide for Gibberella ear rot and vomitoxin control in corn. Miravis Neo (a combination fungicide of a triazole, an SDHI, and a strobilurin) also looks promising.
Q: Is there any relationship between using a strobilurin for vomitoxins in corn compared to what is found in wheat?
The Agronomic Crops Team will host a virtual Corn College and Soybean School on February 11, 2021. Corn College is in the morning, from 9:00 – 12:00pm, with Soybean School in the afternoon from 1:00-4:00pm. Each program will feature updates from OSU Specialists. CCA CEUs are available. The schedule for the day is as follows:
Corn College, 9:00am-12:00pm
Soybean School, 1:00-4:00pm
This program is free to attend. Register at www.go.osu.edu/agronomyschools.