When you fill your planter this spring with seed beans, will you be planting a $12-$15 crop, or will you be burying seed, never to be seen again?

That is a frightful thought, given the investment you are making in planting soybeans, and particularly if you have your crop booked at the premium prices being offered earlier this year. But this is the year that soybeans could face a serious production challenge.

A few years back movie goers were entertained, thrilled, and terrified by “The Perfect Storm.” That is the label being applied to the 2008 soybean crop by agronomist Palle Pedersen and plant pathologist Alison Robertson of Iowa State University. Their concern: soybean seedling disease. Your concern: soybean seedling disease, also.

The whole issue really begins last year in soybean seed production fields managed by many different seed companies. Environmental issues reduced the vitality of the seed coat, and through the conditioning process over the winter, seed beans are not in the best of shape. The Iowa State specialists warn that the lower quality seed results from a variety of factors that all converged on 2008:

• Increased demand for seed beans because of more acres to be planted.
• Fewer quality seeds because of increased rejection of seed last fall.
• High prevalence of seedborne fungal infections
• Lower germination rate due to the thin seed coat cracking during conditioning.

They are quick to say that if the germination rate is low due to fungus, that can be addressed with a seed treatment. The damaged seed coat cannot be glued back together.

The diseases your soybean crop faces are the common ones that you see every year:

• Phytophthora, Pythium, Rhizoctonia, and Fusarium all come from the soil.
• Phytophthora and Pythium like wet soils.
• Rhizoctonia and Fusarium like dry soils.
• Pythium likes cool soils
• Phytophthora likes warm soils.
• Rhizoctonia likes warmer, still, soils.

Iowa State specialists say if the germination is less than 90%, then the seeding rate needs to be adjust upward to compensate. Unfortunately, the amount of adjustment is difficult to gauge because of all of the other factors, such as the soil borne diseases.

Since you have booked your beans for a premium price, you have a larger margin in your production costs possibly, so you might consider a fungicide seed treatment. But what should be used? They all do a job, but are not all equal, and do not fight the same fungal problems:

• If you have Pythium and Phytophthora, then use metalaxyl or mefenoxam.
• If you have Fusarium, Phomopsis or Rhuzoctonia, then use azoxystrobin, captan, carboxin, fludioxonil, PCNB, thiram or thiabendazaole.
• If you don’t know what fungal problems you have had in the past, use a combination treatment.

Pederson and Robertson want you remember, “Fungicide seed treatments will not improve germination of seed that has poor quality and lower germination as a result of mechanical damage because of a thin seed coat, cracked seed coat and other physiological factors.” They are unaware of any data that shows germination rates are lowered as a result of pre-treatment, but warn that fragile seed can be further damaged during treatment.

Finally, they offer a checklist that will help you work toward success:

• Get a good stand and avoid having to replant, since that lowers yield potential.
• Know the condition of the seed, particularly the germination of your seed lot.
• Be patient and do not plant into cold, wet soils.
• Consider a fungicide seed treatment and avoid “the perfect storm.”

Summary:

There is an increased risk to the vigor of the soybean crop because of poor seed coats that might have been damaged, as well as the increased chance for soil borne fungal diseases. Knowing the fungus that has been in your soybean field in the past will help choose a fungicide seed treatment, which is recommended, due to the fragile nature of the seed.

Be patient in planting, and avoid cold wet soils, which may foster fungal problems.

Stu Ellis

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