Each year we are faced with the possibility of a number of early season soybean root diseases that can cause problems from need to replant to significant yield loss. Some of these diseases can be managed by careful variety selection and others may need additional inputs such as fungicide seed treatments. In selecting seed, yield potential is understandably the first consideration. However, the next factors you should consider are what kind of disease resistance the variety offers or what additional disease management may be needed for early season problems.

Seed and seedling diseases can take advantage of both wet and cool and wet and warmer seedbed temperatures, which fairly accurately describes nearly all springs. So especially if you have some history of early season disease you should prepare for it ahead of time. Can you reduce the chance that you will have to replant a field because of early season disease?

The majority of soybean seed sold is not treated with a fungicide. Treating seed by your self is not an easy undertaking but it can be beneficial to getting the crop off to the best start possible. Several fungal seedling blights cause serious problems in soybeans. Diseases such as Pythium root rot and the seedling phase of Phytophthora root rot can outright kill seedlings. Other common seedling diseases such as Rhizoctonia and Fusarium root rots usually are not quite as dramatic but can place the seedlings under considerable early season stress. Seedling death or poor root establishment due to infection by any of the diseases will probably lead to the need for replant.

Several factors lead to an increased risk for serious seedling blight. First, consider the past disease history of the field. These seedling diseases all reside in the soil, you cannot rotate away from them, and with the right environmental conditions they will be active. Environmental conditions that pose a high risk for seedling blights include above normal rainfall the week before planting and above normal rainfall 96 hours after planting. Also, if low areas of the field remain flooded for 48 eight hours after a 1 inch rainfall, this presents an extremely conducive condition for disease development.

Several production practices also can lead to high risk for seedling disease. No till and conservation tillage poses more risk than conventional tillage. Double cropping soybeans and seeding at less than 55 pounds of seed per acre also have increased risk. Do you like to get your soybeans planted early? Seedbeds with delayed germination or emergence are also at increased disease risk.

The quality of the seed is very important as well. If cold germination tests for your seed were less than 70% or less than 85% for a warm germination test you will have increased risk for disease. There is only disease resistance to Phytophthora seedling blight so be careful in your variety selection. Varieties listed as tolerant have tolerance to the adult plant phase of Phytophthora but not to the seedling blight phase. Also, selection of a Phytophthora resistant variety will not protect you from any other seedling diseases they need to be managed separately. Consider each of these factors, and the cost of replanting, to decide if a fungicide seed treatment in addition to resistant variety selection would be beneficial to your soybean production this season. Look for extensive information on soybean varieties at the Varietal Information Program for Soybeans website http://www.vipsoybeans.org/.