SEVERAL SPECIES OF ERGOT fungi attack grasses in the United States.

Claviceps cinerea infects curly-mesquite (Hilaria belangeri) and tobosa grass (H. mutica) in the Southwest. Claviceps tripsaci occurs on eastern gamagrass, Tripsacum dactyloides, in the Southeast. Claviceps paspali is restricted to members of the genus Paspalum. The most common and important species, Claviceps purpurea, causes the ergot disease in about 150 different grasses throughout the United States.

Ergot has retarded seed production of grass desirable for regrassing programs. Seed production of big bluegrass, Poa ampla, was discontinued in Union County, Oreg., because of such heavy infestations that harvesting and cleaning were difficult. Production of seed of some grasses in the Great Plains is often a failure because of sterility due to ergot. Most of the seed often is blighted, although only a few sclerotia may develop.

Ergot poisons livestock that graze heavily diseased grass inflorescences and feed on contaminated seed screenings. Substances in the ergot sclerotia cause abortion, nervous disorders, blindness, and paralysis. In gangrenous ergotism there is a sloughing of the hoofs, tips of ears, and tail; shedding of teeth and hair; and death.

Ergotism in man is no less severe. The disease is contracted usually by eating rye bread made from contaminated flour. Epidemics in humans were common in the Middle Ages.

Modern methods of grain cleaning permit the removal of ergot to within the tolerance of 0.3 percent by weight set by the Federal grades and pure food laws. This has almost eliminated the disease in man, although local epidemics occurred in France and India in 1951.

The ergot fungus attacks only the developing seeds of grasses. It has economic importance when the susceptible grasses are grown for seed or are allowed to flower and seed before grazing or cutting for hay. Ergot is of no importance in seed for planting lawns or other clipped turf.

The first sign of ergot infection appears at flowering time when a sweet exudate, "honeydew," is noticeable. Infested heads feel sticky when drawn through the hand. The exudate, which contains the asexual spores (conidia) of the fungus, attracts flies and other insects. conidia carried by such insects to healthy heads or spread by rain in the same head start new infections. As the infection progresses, purple or blue-black horny bodies (sclerotia) develop in place of seeds. These sclerotia may fall to the ground or be harvested with the seed. When planted or left on the soil they produce specialized sporebearing organs that eject spores into the air. The spores are then carried by wind to grass flowers and infect the young seeds, thereby repeating the disease cycle the following spring.

Many grasses are susceptible to ergot, Claviceps purpurea, and wild grass may serve as sources of infection for grass seed or grain crops.

Control of ergot involves avoidance of the airborne primary spores or the secondary spores spread by rain and insects. This can be accomplished by planting nonsusceptible crops, deep plowing to bury the sclerotia too deeply for emergence of the spore organs, clipping grass before seed heads bloom, and eradication or preventing the heading of grasses in fence rows or other adjacent waste areas. Deep planting, permissible with the larger grass seeds, will prevent emergence of the sporebearing organs from the ergot sclerotia. However, selection of ergot-free seed, removal of ergot sclerotia by seed cleaning with specific gravity separators, or aging the seed for 2 years would be preferable.

Some grasses, such as the bents, produce their flowers in midsummer when the soil is too dry in many areas for development of spore organs from sclerotia. Under such conditions, infection depends entirely on spores carried by insects that have visited the spore slime on grasses infected earlier; control of the offending insect carriers could prevent ergot infection.

Ergot in perennial ryegrass has been materially reduced in western Oregon by burning the fields after the seed harvest. The fire destroys many of the ergot sclerotia in the straw and stubble and also prevents regrowth head formation in the late summer and fall. Such late-formed spikes are usually abundantly infected even in the years. that are dry.

ALTHOUGH infection starts in the spring on the early-flowering grasses, the heaviest ergot infestations occur in the fall in many areas. The phenomenon is due to recurrent heading of many grasses, which become infected by insect-carried spores. This is important, because of the increase in sclerotia that furnish inoculum for infection of grass-seed crops the following spring. Such heavy infestation in late-grass heads is especially dangerous to livestock, because leaf growth is at a low ebb and grazing is heavy on the infected inflorescences.

JOHN R. HARDISON, a graduate of Washington State College, obtained his doctorate in plant pathology at the University of Michigan. He has been engaged in work on forage-crop diseases since 1942. He is employed jointly by the division of forage crops and diseases of the Bureau of Plant Industry, Soils, and Agricultural Engineering and the Oregon Agricultural Experiment Station with headquarters at Corvallis.

Endotbiaparasitica: a, Cross-section of a fungus mass (stroma) showing perithecia; b, saclike membranes (asci), in which ascospores, c, are produced.