Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2004
Publication Date: 9/30/2004
Citation: Pfender, W.F. 2004. Effect of autumn planting date and stand age on severity of stem rust in seed crops of perennial ryegrass. Plant Disease.2004. v. 88. p. 1017-1020. Interpretive Summary: Stem rust is the most damaging disease of perennial ryegrass grown as a seed crop. Disease management is achieved through fungicide applications, because there is no adequate host genetic resistance to the disease. Effective cultural control methods could supplement disease management options. This research demonstrated the importance of autumn planting date in determining severity of the stem rust epidemic that occurs the following spring. Perennial ryegrass stands planted late in the autumn had only 3% as much stem rust in June as stands planted early in the autumn. A disadvantage to late planting is that seed yield of late-planted stands were lower than yield of early planted stands. However, results indicate it may be possible to select an intermediate planting date that provides disease management benefits without sacrificing yield. Delayed autumn planting date may provide a useful cultural control method for stem rust in first-year stands of perennial ryegrass seed crops, thereby reducing the number of fungicide applications required to manage the disease.
Technical Abstract: Perennial ryegrass (Lolium perenne L.) grown for seed is planted in autumn for July harvest (first-year seed crop), then kept in production for subsequent yearly harvests. Plots of first-year perennial ryegrass planted in early November had only 3% as much stem rust in June as plots planted in mid-September. In additional plots where fungicides were used to prevent rust development, seed yield of the November-planted plots was reduced by 23% compared to September-planted plots. In one year of the study, a planting in mid-October produced plots with low rust severity (equivalent to rust level in November-planted plots) and full seed yield potential (equivalent to that in September-planted plots). In the second-year seed crop, stem rust severity in June was intermediate between severities in early- and late-planted first-year plots. The association of reduced stem rust severity with late planting for first-year crops was observed for 5 of 6 perennial ryegrass cultivars tested. Degree of reduction in disease severity due to planting date was greatest for the cultivars that had the highest disease severity in early-planted stands. Delay of autumn planting date may provide a useful cultural control method for first-year stands of perennial ryegrass seed crops.