Is there a cost to Seed Treatment?

Mar 23, 2020

               We’ve all got the question before when booking or picking up seed in the spring, do you want that treated?  The common assumption is soil disease infections occur in cool, wet soils.  The last two decades of university research suggest it may not be that simple.  Here’s a breakdown of four of the most common soil borne diseases found in North Dakota and why they are difficult to control without the help of a seed treatment.
               Phytophthora root rot is a disease specific to soybeans, commonly found in fields that have grown soybeans in the past, and often misidentified as water damage.  There are more than 40 different races of PRR, but in North Dakota race 3 and race 4 are predominant.  PRR can live in the soil a very long time without a host, making crop rotations an ineffective method of control.  PRR infections can occur in the seedling stage all the way through harvest as soil temperature is not the driving factor, soil moisture is the driving factor behind infections.  Most soybean varieties have PRR resistant genes bred into them and different genes provide resistance to different races of PRR.  Early growth stages are when the soybean plant is most susceptible to PRR infections even with a resistant gene bred into the variety.  Seed treatments containing metalaxyl, mefenoxam, ethaboxam, or oxathiapiprolin is your best defense against early season PRR and the resistant gene will take over as the season goes on.  Tillage may help with early season PRR because tilled fields dry out faster than reduced or no till fields.  If your tilled field is saturated than there’s still risk of PRR infection.
               Rhizoctonia is generally a seedling disease and does the most damage early, but can occur in older plants.  Cool, wet soils at or shortly after planting are favorable conditions as are warm soils in late May and June.  Like PRR, there are multiple groups of Rhizoctonia, but the most common found in corn and soybeans are AG 4 and 5.  Rhizoc can live in the soil for a very long time as sclerotia bodies or mycelium on plant residue.  Infections can cause reduced tolerance to stress such as drought, hail, fertility, or herbicide later in the season.  Crop rotation to a small grain can help reduce severity of infections.  Tillage, which dries out fields, will help with severity.  Soybeans affected by IDC can have a more severe infection of Rhizoc.  Seed treatments containing fludioxonil or sedaxane are great options for early season control of Rhizoctonia.
               Pythium can infect a wide range of crops including corn, soybeans, and small grains rendering crop rotation ineffective.  It can cause seed rot, root rot, or both.  Pythium survives for a long time in the soil as oospores.  There are 27 different species of Pythium, but only 7 are commonly found in North Dakota.  Different species of Pythium are more or less aggressive at different soil temperatures.  This means the species in your field will determine if the infection occurs at colder or warmer soil temps. Like PRR, Pythium will always need soil moisture to infect a plant.  Young plants are most susceptible to Pythium infection because the plant tissue is less thick than older plants.  Like previously mentioned diseases, tillage can reduce severity.  There are no resistant varieties to Pythium.  Seed treatments containing mefonoxam, metalaxyl, or ethaboxam are great options for control of Pythium.
               Fusarium can infect a wide range of crops such as corn, soybeans, and small grains.  There are 22 different species of Fusarium and it is commonly found in North Dakota.  Fusarium often piggy backs with another disease meaning a different disease infects a plant and then Fusarium comes along and infects it as well.  Infections can occur throughout the season.  In the early part of the season, cool and wet soils favor infections.  In the later season, dry conditions favor Fusarium infections.  Fusarium can survive in the fields for a very long time.  Fusarium is difficult to control with tillage due to the favorable conditions changing as the season goes on.  A seed treatment containing Fludioxonil is the best protection against Fusarium infections.
               It’s difficult to measure ROI of seed treatments because most fields don’t have an untreated check or vice versa.  Matching active ingredients to the disease your trying to control and balancing how much a.i. you are getting for the money is another challenge. I look at seed treatments like auto insurance, you have partial and full coverage.  A bushel to a bushel and a half investment gets you full coverage and peace of mind that no matter what happens you’ll be covered. 

This article is an opinion and not a base for trade decisions.  Allied Agronomy and the author are not responsible for decisions made based on this article.

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