HPIPM:Charcoal Rot Sunflower

Taxonomy

Domain	Eukarya
Kingdom	Fungi
Phylum	Ascomycota
Subphylum	Pezizomycotina
Class	Dothideomycetes
Order	Botryosphaeriales
Family	Botryosphaeriaceae
Genus	Macrophomina

Scientific Name

Macrophomina phaseolina

Scientific Name Synonyms

Macrophomina phaseoli

Sclerotium bataticola

Botryodiplodia phaseoli

Tiarosporella phaseolina

Rhizoctonia bataticola

Macrophoma phaseolina

Common Name

charcoal rot

Author: Howard F. Schwartz and David H. Gent

Identification and Life Cycle

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.

Plant Response and Damage

Symptoms of Macrophomina phaseolina usually begin to appear after flowering. The first symptoms are a general wilting of the plant during the midday heat followed by a recovery in the evenings 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 stalks of infected plants eventually take on a gray discoloration at the base. Internally the pith decays leaving only the water conducting vascular bundles. This gives the internal stem a shredded appearance. Later, the vascular bundles may become covered with small, black flecks or sclerotia of the fungus. The disease can be economically important in the High Plains during hot, dry seasons.

Biological Control

No biological control strategies have been developed for charcoal rot.

Cultural Control

Practice a four-year or longer crop rotation between susceptible crops; wheat rotations provide some disease reduction. Select varieties that do not flower and head 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.

Chemical Control

No fungicides are registered for charcoal rot management.

The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.