Rob Leeds: Seed treatment for molds, fungi essential


Rob Leeds - OSU Extension



Seems like the weather pattern has been all over the place these last few months. After a record warm December, colder weather returned to us in January with temperatures running just below normal.

According to the National Weather Service, we can expect a pattern change towards warmer and slightly wetter conditions into the first half of February. Drier weather is expected but still above normal temps for the end of February.

I wanted to remind those of you who need to recertify for your pesticide license this year about our class in Delaware County which is scheduled for Feb. 15 at the Radnor Township Hall in Radnor from 9 a.m. to noon. There is a cost of $35 and you need to call into the office at 740-833-2030 to register.

On Feb. 24 from 9 a.m. to 4 p.m. at Evolution Ag in Plain City, OSU Extension Delaware County will be hosting an “Intensive Soybean Management Workshop.”

This workshop will take an in-depth look into management including row width, seeding rates and yield components. Soybean insect management will cover late-season pests and seed treatments. The soybean fertility section will look into updating the Tristate Fertility Recommendations. Soybean cyst nematode will be covered in the disease section along with seed treatments. CCA credits and Pesticide credits (private and commercial) will be available. The registration form and payment is due Feb. 19 and can be found at http://delaware.osu.edu/news/upcoming-ag-programs. The cost is $70 which includes publications and lunch. For more information and to register, please call our office at 740-833-2030.

Seed treatments for watermolds and fungi are essential for central Ohio’s poorly drained soils.

Much of our soybean production ground is on soils with poor to fair drainage, high clay content and reduced tillage systems. Any one of these factors alone or in combination contributes to the environmental conditions that favor infection of seeds and seedlings by watermolds.

According to Anne Dorrance, OSU Extension specialist, reduced tillage systems favor pathogen build-up in the very place that the seed is planted each year. Both soybean and corn are attacked by a great diversity of Pythium, some of which are favored by cool, wet soil conditions and others by warmer but also wet soil conditions.

Of course for soybean, Phytophthora can be recovered from all of Ohio soils and this is favored by warmer temperatures and wet soils. True fungi, Fusarium and Rhizoctonia, are also pathogens of soybean and corn but, for these, the amount of inoculum that is present in the field and adequate moisture for pathogen growth are all that is needed to favor infection of both corn and soybean.

Dorrance says that host resistance is the primary means by which we manage many grain crop diseases. However, other than virguliforme, which causes sudden death syndrome of soybean, there is little effort put into screening for resistance towards Pythium, Fusarium and Rhizoctonia solani in comparison to other diseases. This is where seed treatments aimed at watermolds and true fungi can play a big role for fields which are high risk for these seed and seedling pathogens. This protects the seed and seedling when they are the most susceptible since, for some of these diseases, host resistance is not expressed in the early plant growth stages. How do you know if your field is at risk? It is a very simple question to answer:

1. How many times in the past 10 years have you had to replant? If it is more than one, then you are always at risk.

2. Are you planting into a field that had head scab of wheat or Gibberella Stalk rot of corn? If the answer is yes, then it is important to add fungicide seed treatments specific to Fusarium to limit stand losses.

With a seed treatment, it is important to note that no one seed treatment active ingredient will provide protection against all of the pathogens that attack seeds and seedlings. As you examine the list from your seed dealer, you will see a long list of active ingredients, each of which is targeting a small portion of the total grain crop pathogen complex that Ohio farmers must deal with on an annual basis.

So which seed treatment package is best? Dorrance says that in reality the companies have been testing numerous combinations, formulations and sites to get this right. None of them are perfect. There is a growing number of Pythium species that can get past the protection, but they are in the minority. We do have a number of Pythiums which are resistant to metalaxyl/mefenoxam and we know for Phytophthora sojae that higher levels of metalaxy/mefenxoam — 0.75 to 1.5 fluid ounces of metalaxyl and 0.32 to 0.64 fluid ounces of mefenoxam — are better. So for those fields having a different active ingredient, such as ethaboxam, or adding a strobilurin will pick up a few more of those Pythium variants. For example, in the seed treatment trials during 2015, we can’t really separate the difference among the seed treatments when there was very high disease pressure. All of the seed treatments had significantly higher yields than the non-treated.

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Rob Leeds

OSU Extension

Rob Leeds is the Ohio State University Extension educator for agriculture and natural resources in Delaware County.

Rob Leeds is the Ohio State University Extension educator for agriculture and natural resources in Delaware County.