Cotton Root Rot Symptoms on Carrot

Cotton Root Rot (fungus - Phymatotrichopsis omnivora): Carrots are usually grown during cooler times of the year when this fungus is not active and so, they escape this disease. In geographic areas where this pathogen is present, the disease can be seen later in the spring on carrots growing in lighter soils, particularly following an irrigation. Areas of dead and wilted plants are seen in a field. These resemble the dead areas that can also be caused by the southern blight fungus, but there is no fungal growth on the surface of the soil [Photo #12]. When carrots are pulled out, they are not rotted and a sheath of soil clings to them [Photo #13]. When this soil is removed, infection cushions and mycelial strands of the fungus can be seen on the surface of the carrot [Photo #14]. A microscopic examination for the the characteristic cruciform hyphal branching will confirm the diagnosis. Planning for an earlier harvest will prevent disease losses.