Evaluate Fields For Yield-Robbing Soybean Diseases
JOE BUNCK
LUBBOCK, TEXAS
Soybean seedling diseases are a significant factor in reduced stand establishment and can cause economic losses. Early assessment of your soybeans allows you to take management steps to reduce seedling disease. Management options for reducing disease include selection of disease-tolerant products, crop rotation, adjusting planting dates and using seed treatments. Growers interested in better seedling health can apply soybean seed treatments at planting.
Here are the most common early, yield-robbing soybean diseases:
• Pythium infected soybean seedlings are found in low pockets, heavy, wet soils and thick-residue areas. Plant death occurs in random plants or in small patches. Look for damping off of pre-emergent plants and seedlings that are water-soaked and soft to the touch. Other symptoms include gray-green leaves that turn brown with death.
• Phytophthora Root Rot (PRR) is most severe in poorly drained soils or high clay soils with temperatures of 70 to 80 degrees F. Look for stems girdled by a continuous dark chocolate-brown lesion. Multiple races of PRR exist and management requires knowledge of those most prominent in the field.
• Rhizoctonia can affect soybean plant growth at any time, but is most severe in the early season. Typically, the disease is found during warmer temperatures on slopes and sandy, well-aerated soils. Scout for seedlings that are dampened off after emergence or hypocotyls with a reddish-brown, slightly sunken lesion near soil level. Later on, lesions spread to roots and cause root rot.
• Fusarium appears in conditions ranging from hot and dry to cool and wet. Twenty species of Fusarium exist and all cause poor to slow emergence, leading to stunted seedlings. Identified by a reddish brown discoloration that causes roots to appear dry and shrunken, symptoms affect the taproot and are not visible above the soil line. Leaves appear torched, wilt and fall off of plants.
• Charcoal Rot is not typically an early-season disease, as it generally appears in hot, dry weather, but it can infect developing seedlings. Symptoms can be seen on the lower stem and color varies from reddish brown to black.
For more information about soybean seedling diseases, contact your Channel Seedsman or visit the Agronomy Library at channel.com. Sign up for agronomy alerts by texting JOIN to CHANNL (242665). Messaging and data rates apply. ∆
JOE BUNCK: Channel Technical Agronomist