DISEASES OF SOYBEAN - PHYTOPHTHORA ROOT ROT

Growth of Phytophthora sojae is favored by wet soil conditions. Therefore, proper soil drainage is important for control of this disease.

Crop rotation is not effective. Resting spores (oospores) of P. sojae can survive for many years in soil in the absence of any soybean plants.

The most important method of Phytophthora root rot control is the use of resistant soybean varieties. Resistance however is race specific. This means that plants that are resistant, are resistant to only a certain group of P. sojae (called a race), and not all P. sojae, found in the soil. Therefore it is critical to have soil tested prior to planting to determine which races are present. Based on these findings, a grower can more intelligently select the appropriate variety of soybean to minimize the impact of the disease.

This photo shows a trial of two varieties of soybean, one (on the left) that has resistance to the race of P. sojae present at the site and one (on the right) that does not.