Fusarium Root Rot
Root rot is a key problem for Michigan growers. Fusarium root rot initially appears as red to reddish brown streaks (lesion) on the hypocotyl and primary root (tap root) 2-3 weeks after planting. These affected areas enlarge with age, many merge and gradually become brown. These symptoms may extend up the main root and hypocotyl to the soil surface, and longitudinal cracks can develop in older lesions. Severely infected primary and secondary roots are commonly killed but can persist on the plant as dried remnants. Lateral roots can develop from the hypocotyl above the initial infection site if sufficient soil moisture is available. Plants are seldom killed by the fungus, but may be stunted with yellow leaves.

Root rot severity depends on factors such as cropping history, plant spacing, moisture and temperature stresses, and soil compaction. In general, any factor which contributes to a reduced rate of root growth increases the plant's susceptibility to Fusarium root rot. Early planting in cool, moist soil favor the disease, as does soil compaction in the form of tillage or hardpan layers. Improper cultivation, other soil-borne pathogens, and various herbicides are also know to induce injury of young roots and aggravate Fusarium root rot damage. The effect of Fusarium root rot is usually more apparent during blossoming and early pod set when the plant and its productivity are most sensitive to stress.

Certified seed of Fusarium root rot tolerant or resistant varieties is recommended. Rotation of beans with non-host crops such as corn, wheat, barley, or alfalfa will usually reduce root rot severity. Plants are spaced within the row to reduce plant competition for water. Soil is tilled around the base of infected plants to enhance lateral root development above infected portions of the hypocotyl.