How prevalent are the fungi that cause seedling disease?
Continued soybean cropping has increased populations of the soilborne fungi Pythium spp. and R. solani. Contamination of seed by Phomopsis/Diaporthe is most serious when harvest delays the previous season are accompanied by warm, wet weather, resulting in a high proportion of infected seeds. Do not use such seeds for planting purposes. • How can you recognize seedling diseases? The damage these fungi cause at times may be confused with herbicide damage, effects of low pH, or other seedling disorders. The following should help in recognizing seedling disease. • Pythium causes seed rot or kills young seedlings before or shortly after emergence. The infected areas of the root are soft but rapidly turn brown, and tissues slough off to leave a “wire root” appearance. • Rhizoctonia on roots frequently kills young soybean plants. Look for sunken reddish-brown areas on the main and upper roots near the soil line, which resemble “sore-shin” on cotton. The infected area is firm, in contrast to P
