Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: January 25, 2000
Publication Date: N/A
Technical Abstract: Growth of forage crops on animal waste disposal sites under conditions of high soil fertility and abundant moisture highly favors development of plant diseases. These reduce the vigor, productivity, and survival of desired forage species and impede nutrient removal. When plant diseases are severe, they may become the major determinants for forage species composition on waste disposal sites. In recent years, fungal diseases have been observed on bermudagrass (Cynodon dactylon [L.] Pers.), johnsongrass (Sorghum halepense [L.} Pers.), foxtail millet (Setaria italica [L.] Beauv.), and signalgrass (Brachiaria platyphylla [Griseb.] Nash) on swine- and poultry-waste application sites. Bermudagrass has been most commonly affected, and when disease is severe, it appears to spread to the other forage species. Diseases on bermudagrass are caused primarily by species of Exserohilium, Bipolaris, and Curvularia; Drechslera, Colletotrichum, Nigrospora, and Phoma spp. also may contribute to disease development. In greenhouse experiments, naturally occurring disease significantly reduced dry matter production of bermudagrass by 48-63%. Preliminary observations also indicate that when diseases severely weaken or destroy portions of a stand of bermudagrass, it then may become heavily colonized by johnsongrass, foxtail, signalgrass, and other species. These volunteer forages then become dominant and cause conversion of the stand from bermudagrass. Breeding new varieties of bermudagrass with resistance to major fungal diseases may be necessary to maximize its survival, forage production, and nutrient removal on animal waste disposal sites.