"I’m not discouraging early planting. It’s just important for producers to be mindful that yield advantages of early planting may be offset somewhat by disease problems," said Doug Jardine, plant pathology state leader for K-State Research and Extension.

Three potential problems to watch for if planting soybeans early this year are: sudden death syndrome, bean pod mottle virus, and seedling blight, he said.

Sudden death syndrome [SDS], which is caused by a strain of the fungus Fusarium solani, is favored by cool, rainy weather during the first half of the growing season. It is difficult to manage, Jardine said, and early-planted beans tend to be more heavily damaged than later-planted beans because more favorable conditions for infection by the fungus exist early in the season.

Irrigated fields, which remain wet throughout the season, typically have a higher incidence of SDS than non-irrigated fields, he said. No pesticides have been found to control the disease.

The name sudden death syndrome is somewhat misleading in that the disease may take up to 14 days to develop, and symptoms, which begin as small yellow spots on the plant’s upper leaves, may not show up until the disease is well advanced. Time from defoliation to death, however, is short, which may account for the "suddenness" of the disease.

One way to counter the risk of SDS is to extend planting times so that all beans are not at the same stage of development at the same time, Jardine said. He cautioned, however, that growers not wait past the suggested time for their area of the state to plant.

In Illinois, deep ripping of compacted soils has resulted in reduced levels of SDS, but similar tillage on non-compacted fields did not provide any added benefit.

Tolerant varieties are available, according to Jardine, but ratings of the varieties most frequently grown in Kansas are not readily available. Growers with a history of SDS problems should consult with seed company representatives for information on SDS tolerance.

Jardine added that SDS is nearly always associated with the presence of soybean cyst nematodes in a field. Management of cyst nematodes, therefore, can also reduce losses to SDS.

Bean pod mottle virus can infect soybeans and other legumes and cut yields by as much as 50 percent or more, according to some studies. That varies, however, by soybean variety and growing conditions. The main transmitter of the disease is the bean leaf beetle.

Early symptoms of infection include greenish-yellow mottling and puckering of the leaves. These symptoms usually fade with the higher temperatures of midsummer. Late in the season, bean pod mottle virus can cause the plants’ stems to remain green long after the pods mature. A high percentage of green stems can cause harvest problems for growers because they are more difficult to combine.

The best way to manage the virus is to manage the beetle, Jardine said. If bean leaf beetles were abundant in a farmer’s fields last year, they may have survived this winter. Use of an early-season insecticide is a possibility although data is sparse regarding the effectiveness of such treatments.

Another management method is to plant soybeans later in the season to deter colonization of fields by the first generation of the beetles. Delaying planting until mid-to-late May can reduce bean leaf beetle densities in a field, which in turn may reduce the incidence of disease in the crop.

Seedling blights also can be more problematic when planting soybeans early, Jardine said. The soil-borne pathogen Pythium is most often responsible for early-season seed rot and seedling blight when soils are frequently cool and wet.

"Products containing the active ingredient metalaxyl or mefanoxam are highly effective in limiting losses to Pythium," the scientist said.

Allegiance, and ApronMaxx are products labeled for use in Kansas containing metalaxyl or mefanoxam.

As soils warm and if wetness continues, Rhizoctonia becomes a major pathogen of concern. Rhizoctonia can be difficult to control, but products containing the active ingredients thiram, PCNB or fludioxonil have given the best control in our annual seed treatment evaluations, Jardine said.

Products labeled for use in Kansas containing one of those materials include Agrosol-T, ApronMaxx, Rival, Vitavax 200, and RTU Vitavax-Thiram.