soybeans showing signs of seed decay

Soybeans with purple seed stain (left) and soybeans showing signs of seed decay due to Phomopsis disease complex. 

Editor’s note: The following was written by Steve Knox, manager of the Nebraska Crop Improvement Association, Tamra Jackson-Ziems, University of Nebraska Extension plant pathologist, Roger Elmore, Extension agronomist, and Thomas Hunt, Extension entomologist, for the university’s CropWatch website Feb. 13.


Some new crop soybean seed being tested by the Nebraska Crop Improvement Association is falling below the normal germination rate. While a few lots came in at or above 95 percent germination, results are averaging in the mid-80 percent range.

Growers are urged to check the germination rate for their soybean seed, adjust planting rate accordingly and use fungicide treatments under certain circumstances. Seed treatment fungicides might be recommended when growers are planting early into cold soils or have had chronic problems with seedling diseases.

In a typical year, soybean seed lots tested by the Nebraska Crop Improvement Association range from 88 to 98 percent germination. This year samples ranged from 43 to 98 percent germination.

The minimum germination for certified soybean seed is 80 percent, as set by the Association of Official Seed Certifying Agencies.

In uncleaned samples submitted to NCIA, there were a lot of dead, moldy seeds this year. These were cleaned out before germination testing, similar to what would happen in commercial seed production.

Concerns over soybean seed quality issues are widespread across the U.S. production area due to an unusually wet fall that delayed harvest in seed-producing areas of Iowa, Illinois and Indiana. Wet fall conditions contributed to the development of several seed diseases: Phomopsis seed decay and purple seed stain.

In fall 2018, purple seed stain was reported at above-normal levels in Nebraska. There are no known sources of resistance for purple seed stain. But NCIA testing has shown little or no reduction in germination in purple stained seed in its tests this year.

Fungicide treatment

If the germination rate for your seed is lower than normal, consider adding one or more fungicide seed treatments and increasing your seeding rate.

Various seed treatment classes and active ingredients do not work equally well against all pathogens. Thus, it’s important to understand which disease(s) have been or may be problematic in your fields and select products or a diverse combination from multiple fungicide classes.

Efficacy ratings are provided for soybean seed treatments in the 2019 Guide for Weed, Disease, and Insect Management in Nebraska, including for Phomopsis seed decay. Find it online at https://bit.ly/2Tms6ta. This efficacy table was developed by university plant pathologists from throughout the U.S. soybean production area.

A fungicide treatment won’t improve germination of dying or dead seeds, but it can help protect seedlings under stress and thus help ensure a better stand. A fungicide application should be considered for soybeans, especially when the seed germination rate is below normal, you’re planting early into cold soils that may delay germination, or you’re reducing your soybean seeding rate.

Seeding rate

With lower germination rates, how much should the seeding rate be increased?

If you’re shooting for a 120,000 plant-per-acre stand, and the germination rate is 80 percent rather than the 90 percent you usually plant, increase the seeding rate by the relative difference — in this example, by 10 percent.

A lot of things can kill your stand after emergence and you don’t want to short change potential yield early in the season.

Insecticide seed treatments are not warranted in response to expected low germination, but may be warranted for early-planted soybeans in areas where bean leaf beetle feeding might be expected.

Growers also may want to have any seed they’ve stored on-farm over the winter tested again to determine whether storage conditions may have further affected seed quality. Seed molds can die in cool, dry conditions or increase in wet conditions.

Each spring NCIA tests 500 seed samples for the Nebraska Department of Agriculture to see if germination falls within an allowable range of that stated on the seed label. They also conduct germination tests for seed companies and for individual growers. In these recent tests, germination of fungicide-treated seed was slightly higher than non-treated seed.