Cover crops are planted between vineyard rows to control erosion, maintain organic material and influence pest management. Planted cover crops are preferable to resident vegetation (weeds) because they can be selected for beneficial characteristic. Sethoxydim and fluazifop-butyl alone and in combination with 2,4-D were applied in December 1988 and 1989 to release Festuca megalura (Zorro fescue). Untreated plots were mowed to maintain vegetation. Frequency, percent cover and biomass of the vegetation was evaluated to determine species shift. The vegetation was composed mainly of: 1. Festuca megalura, Poa annua with other grasses in minor amounts; and 2. Stellaria media, Centaurea solstitialis, Erodium botrys and Erodium cicutarium
Following sethoxydim or fluazifop-butyl treatments, annual grasses other than Festuca megalura and Poa annua were reduced but Centaurea sp. increased over the length of the experiment. Treatments containing 2,4-D Centaurea and Erodium spp. declined in both frequency and percent cover. The desirable cover crop species (Festuca megalura) increased in all treated plots. No species shift was observed in the mowed treatments. Two applications of selective post-emergence herbicides maintained shift of species over the 5 years of the study.