PLPA-Co-010-02

Head of Corn

Symptoms The plant remains asymptomatic until it reaches Head smut is a systemic disease of corn that the reproductive growth stages, when the starts at seedling stage, and remains pathogen replaces ear and tassel tissues. Ear and asymptomatic until the plant reaches its Tassel tissues may be partially or totally reproductive stage. Symptoms consist of replaced by the membrane covered mass of conspicuous galls that replace ears or tassels. teliospores. The galls are covered by a very fragile Dry and cool weather that delays seedling membrane that breaks early and easily, growth favors the early stages of this disease. exposing masses of dark brown , Once in the plant, dry and warm conditions (70- teliospores, and vascular bundles (Fig. 1). The 86°F) favor fungal development. consistency of the membrane and the presence of vascular bundles are what differentiate head Management smut from common smut. Once the membrane is broken, wind and rain spread the teliospores • Plant resistant varieties. Select Hybrids that into neighboring soil where they stay viable are fast to emerge, thereby escaping infection. for several years. • Plant early, when temperatures are Causal Agent unfavorable for germination.

Head smut is caused by the pathogen • Treat seeds with systemic fungicides. (syn. Sorosporium Protective fungicide seed treatment gives only reilianum, reiliana, Sporisorium reduced control. holci-sorghi). Teliospores of S. reiliana are circular, spiny, and dark brown to black in • Maintain balanced soil fertility. color. Several races of S. reiliana have been recognized that affect hosts including , • Where feasible, remove and burn smutted , Sudan grass, Johnson grass, and tassels and ears as they emerge to reduce teosinte. inoculum spreading.

Inoculum Source and conditions • Only long rotations may be effective due to the longevity of teliospores in soil.

Soil-borne teliospores are the main inoculum

source. Teliospores survive in soil for several

years, and are the source of the mycelium that

penetrates through the seedling root, invades

the meristematic tissue, and develops

systemically.

PLPA-Co-010-02

Fig.1. Vascular bundles and masses of teliospores replace the ear. Photo: Ronald French.

Prepared by Dr. Ronald D. French1([email protected]) and Dr. Diana Schultz2 1Assistant Professor and Extension Plant Pathologist (Amarillo, TX) 2Plant Pathologist (Fort Myers, Florida) Texas AgriLife Extension Service; The Texas A&M System March 1, 2010 The information given herein is for educational purposes only. References to commercial products or trade names are made with the understanding that no discrimination is intended and no endorsement by Texas AgriLife Extension Service personnel is implied. Educational programs of the Texas AgriLife Extension Service are open to all people without regard to race, color, sex, disability, religion, age, or national origin. The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating