HERBICIDES WITH CROP COMPETITION REPLACE ENDOPHYTIC TALL FESCUE (FESTUCA-ARUNDINACEA)

Herbicides and interim summer crop treatments were studied in 1984 to 1987 to replace fungal endophyte-infected with endophyte-free tall fes cue or red clover to improve forage quality. Foliar glyphosate or para quat were applied in spring across interim crops with PRE herbicides. The interim crops, grain sorghum with atrazine, sorghum-sudangrass hyb rid with metribuzin, or soybean with imazaquin, were each applied as c onfounded treatments across glyphosate or paraquat. Within an interim crop system, a follow-up glyphosate treatment was serially applied the next fall or spring. Then either red clover or endophyte-free tall fe scue was spring drilled within the fall or spring glyphosate follow-up treatments. Glyphosate controlled old tall fescue better than paraqua t, and improved the stand of the endophyte-free tall fescue. Control o f tall fescue was 97% from 1.7 kg ai/ha glyphosate. Glyphosate reduced the endophyte from a 77% original infection level to 20% over all int erim crops after drilling the endophyte-free tall fescue. Among interi m crops, grain sorghum or the sorghum-sudangrass hybrid was more compe titive than soybean with the uncontrolled tall fescue. Replacement wit h endophyte-free tall fescue was best in grain sorghum or sorghum-suda ngrass hybrid stubble the next spring. Grain sorghum or sorghum-sudang rass hybrid following foliar glyphosate or paraquat treatment of endop hyte-infected tall fescue reduced endophyte infection level in tall fe scue to 28%. A follow-up fall treatment with glyphosate controlled tal l fescue better than the spring retreatment and red clover and endophy te-free tall fescue were established better from fall retreated glypho sate. Red clover was easily established by drilling into the sod after treating endophyte-infected tall fescue with either glyphosate or par aquat.