Figure 1. Sudden death syndrome is an example of one of the diseases, which is increased by planting early in cool, wet soils. Photo by E. Byamukama.
For most plant diseases, in-season management choices are very limited. In fact, there are no in-season management options available for diseases caused by nematodes, viruses, and bacteria. Careful considerations are therefore needed before planting the crops.
The first item to consider is cultivar selection. A good cultivar can give high yield even when it has moderate disease severity. Currently, cultivars with disease resistance traits do not cost any more than those without disease resistance traits. Growers should carefully select a cultivar to be planted based on the field history of plant diseases. For example, if the field has had sudden death syndrome of soybean (SDS) in the past, consider selecting a SDS resistant cultivar to plant. Seed companies provide a rating of cultivars for tolerance to the different diseases since not all of cultivars have resistance to the different diseases.
The next item to consider is seed treatment. Seed treatment is an important decision to make at planting. Seed treatments provide protection for the seed and seedling against soil-borne/seed-borne pathogens that may interfere with germination or cause seedling death. The common question associated with fungicide seed treatments is usually whether or not it pays for itself. When making the decision on whether or not to utilize a seed treatment, consider field history of poor plant stand, cultivar ratings against the disease being managed, and field conditions at plating (cold temperatures <55 F and high soil moisture at planting increase the risk for seedling root rots).
Consideration should also be given to crop rotation. Crop rotation helps break the disease cycle while reducing the amount of inoculum being built up in the soil. With the exception of a few, the majority of plant pathogens survive in the crop residue and soil. Because plant pathogens can survive in the soil for a long time, three or more crop rotations are considered more effective in breaking the plant disease cycle. Rotations should be between crops that do not share common pathogens.
Time of Planting
Time of planting is another factor to consider when managing certain plant diseases. The risk for some root rots such as Pythium root rot and SDS (Figure 1) increase when planting is done in cool wet soils. Delaying planting until soils are warmer and well-drained (>55 oF) may help the plants escape infection.