Getting a soybean crop off to a healthy, vigorous start is always a recipe for developing high yield potential. Fungicide seed treatments can provide excellent protection against early season soybean diseases. So why has the interest in soybean seed treatments only recently resurfaced?

Soybean seed has a short shelf life and once treated cannot be "dumped" into the grain markets. Seed companies, retailers and producers are reluctant to inventory treated seed that cannot be returned.

Currently, many producers prefer to purchase bulk seed. Many agricultural retailers have purchased seed-treating equipment. This allows for bulk seed to be treated locally, thus eliminating the treated seed inventory dilemma.

Soybean fungicide seed treatments are designed to protect against seed-borne and early season soil-borne diseases. They have limited activity on late season soil-borne or any of the foliar diseases.

Seed treatments rarely help poor physical quality seed or seed lots that are excessively infected with seed-borne diseases. Therefore, do not try to salvage poor quality seed with fungicide treatments.

Soybean seed treatments primarily target four soil-borne pathogens. The "Big 4" are: pythium, phytophthora, fusarium and rhizoctonia. Many growers falsely assume that the only time soil-borne fungi negatively affect soybean growth is under cool/wet conditions. Generally, pythium and fusarium are most active when soil temperatures are below 60 degrees Fahrenheit. phytophthora and rhizoctonia prefer soil temperatures in the 70 to 80 degree Fahrenheit range. pythium and phytophthora prefer saturated soil and periodic rainfall conditions. rhizoctonia and fusarium do not require excessively wet conditions. To complicate matters, these weather requirements are not universal. For example, continuous soybean fields that have high levels of phytophthora inoculum present, often have disease injury even under optimum crop growing conditions.

Varietal selection is often used as a soybean disease management tool. Of the "Big 4", only phytophthora has acceptable varietal ratings. Within-field phytophthora population diversity often leads to tolerant "race shifts" that limit soybean variety selection effectiveness. I prefer to use varietal selection in concert with crop rotation and fungicide seed treatments when planting soybeans into fields with a past history of phytophthora injury.

Resistance management is always a concern when using preventative pesticide programs. With fungicide seed treatments, only a small fraction of the fungal population is exposed to the seed treatment. Therefore, we do not expect to see a population shift toward fungicide-resistant fungal biotypes when using seed treatments.

Crop yield and economic responses to soybean fungicide seed treatments are inconsistent. Under optimum early season growing conditions, soybean fungicide seed treatments may not be cost effective. However, it is very difficult to predict future growing conditions at seed purchase time. Research at The Ohio State University (OSU) demonstrated that the use of soybean fungicide seed treatments increased income 3.5 times more than treatment costs during a 10-year period. They state, "Over time, it pays to use a fungicide seed treatment on soybean seed regardless of variety, crop rotation, tillage, soil type, soil drainage or planting date." If fungicide seed treatment costs $2 to $4 per acre, then $7 to $14 per acre per year return would be expected using the OSU data.

Fungicide seed treatment is not the cure-all and end-all for early season soybean disease management. I agree with MU plant pathologist Dr. Laura Sweets when she says "Once a crop has been planted, there is little that can be done to reduce incidence or severity of soybean seedling diseases. Additional stress from poor growing conditions, herbicide injury or other factors may compound problems with soybean seedling diseases. Prior to planting, it is important to consider variety selection (especially in fields with a history of phytophthora), fungicide seed treatment, crop rotation, seedbed preparation and conditions at planting."

There are many fungicide seed treatment products available. In general, these fungicides can be categorized into those that are active against water mold fungi (pythium and phytophthora) and those that are effective against other soil and seed-borne fungi. Unless you know (and it is very difficult to predict) the targeted fungal organisms before planting, I recommend using a combination of fungicides that have activity on both groups. For example, MFA predominately uses ApronMaxx Bean Pak, which contains Apron XL (active on pythium and phytophthora) and Maxim (active on fusarium and rhizoctonia). If you have fields that are in continuous soybeans or have had severe phytophthora problems in the past, I recommend using higher rates of Apron XL in combination with Maxim.

The bottom line is that soybean fungicide seed treatments should be considered, especially when planting into less than ideal conditions.