Early detection and diagnosis of soybean emergence problems is always important to achieving high yields. This year, early-season scouting is even more important because of a reduction in seed quality. Growers who begin monitoring their fields early can head off potentially costly problems caused by diseases or pests.

"Soybean emergence ranges from six days under ideal conditions to 14 days under more challenging soil conditions," says Mike Staton, Michigan State University Extension agriculture and natural resources educator and Soybean 2010 coordinator. "Those challenges can include cold soil temperatures, excess soil moisture, inadequate soil moisture, soil crusting, improper seeding depth or uniformity, poor seed-to-soil contact, insect feeding and disease infestations."

Staton recommends that farmers who notice fields with slow or uneven emergence should dig up the plants and inspect them for signs of disease or insect damage to the root, hypocotyl or cotyledons.

"In most fields, the major insect pests affecting seedling emergence are seedcorn maggots and wireworms," he says. "If seedcorn maggots have reduced a stand to an unacceptable level, replanting should correct the problem -- the decaying organic material that lured the adults to the field in the first place won't be an issue. If wireworms are responsible, the seed will need to be treated with Cruiser prior to replanting."

Soil-borne diseases such as Phytophthora, Pythium, Rhizoctonia and Fusarium can also damage germinating soybean seed.

Fusarium can survive a wide range of temperatures. It may not kill seed outright but may contribute to stunting and root rot.

Pythium is more likely to create problems under cool, wet soil conditions. It is prevalent in southwestern Michigan soils, and damage is likely to occur when a heavy rain occurs within 24 hours following planting. Its symptoms are swollen and bent hypocotyls. Replanting when soil temperatures exceed 60 degrees should result in satisfactory emergence.

Warmer temperatures (between 75 and 89 degrees F) and drier conditions favor Rhizoctonia.

(68 to 77 degrees F). If seedlings emerged from the soil but died quickly, Phytophthora is a likely suspect, and growers should replant with resistant varieties or fungicide-treated seed.

If no insect feeding or disease symptoms/lesions are present on the seedlings, look for a soil crust. If one exists, Staton suggests using a rotary hoe to break it up, though with caution. It's important to avoid using a rotary hoe when the plants are in the "crook" stage or for three days afterward to prevent damage to emerging seedlings. Large soybean seed is more likely to experience emergence problems in crusted soils than small soybean seed because of its larger cotyledon.

If emergence problems occur but there are no signs of insects or diseases and crusting is not the problem, determine if the planting depth was correct and uniform, and check to see that soil is firmed around the seeds. Some varieties may not emerge well when planted 2 or more inches below the surface. If no planting problems are detected and the seeds/seedlings look healthy, inadequate soil moisture is likely the cause of the delayed emergence. Wait until a rain occurs and recheck the field.

To determine whether replanting is warranted, Staton suggests farmers compare the yield potential of the existing stand to that of the replanted stand and take into

"Yield losses of 0.6 of a bushel per acre per day have been shown to occur when planting is delayed after mid-May," he says. "A uniform stand of 100,000 plants per acre will produce good yields, and because seed supplies are short this year, a high-yielding variety may not be available as we get further into the season."

For more information about soybean emergence problems, contact your county

For more information about improving Michigan's soybean crop, visit the Soybean 2010 Web page at web1.msue.msu.edu/soybean2010/. Soybean 2010 was developed to help Michigan growers increase soybean yields and farm profitability by 2010. Funding is provided by MSU Extension; Project GREEEN (Generating Research and Extension to meet Economic and Environmental Needs), the plant industry initiative at MSU; and the Michigan Soybean Promotion Committee.