Charcoal rot is caused by the fungus Macrophomina phaseolina. The disease can be damaging when soil temperatures exceed 90o F and plants are drought stressed. Microsclerotia can survive in the residue for several years. Charcoal rot has a wide host range, including corn and sunflower.
Symptoms of Macrophomina phaseolina usually begin to appear near flowering. The first symptoms are a general wilting of the plant during the mid-day heat followed by a recovery in the evening as temperatures decline. Eventually the wilt becomes permanent and the plant dies. Since charcoal rot restricts the flow of water and nutrients to the head, reduced seed size and light test weight usually occur. The taproots of infected plants eventually take on a gray discoloration at the base, and have a shredded appearance. Later, the vascular bundles may become covered with small, black flecks or microsclerotia of the fungus. The disease can be economically important in the High Plains during hot, dry seasons.
No biological control strategies have been developed for charcoal rot.
Practice a four-year or longer crop rotation between susceptible crops; wheat rotations provide some disease reduction. Select varieties that do not mature during the hottest part of summer. Conserve soil moisture by reducing planting populations, practicing minimum tillage, and controlling weeds. Provide irrigation, if possible, during the hottest and driest times of the year to reduce plant stress.
No fungicides are registered for charcoal rot management.
Categories: Canola and Mustard, Disease, Charcoal Rot
Date: 12/30/2004