INFLUENCE OF FOLIAR-APPLIED FUNGICIDES ON SEED YIELD OF FABA BEAN (VICIA-FABA L) IN NORTHERN NEW-SOUTH-WALES

The effects of 5 foliar-applied fungicides on seed yield of faba bean (Vicia faba) cv. Fiord were studied over 3 years at Tamworth in northern New South Wales. In 2 seasons when the diseases chocolate spot (Botrytis fabae) and rust (Uromyces viciae-fabae) were significant, 5 applications of foliar fungicides after flowering increased yield, by up to 1.6 t/ha in 1990 and nearly 0.9 t/ha in 1992, compared with the unsprayed treatment. Mancozeb, dichlofluanid, and tebuconazole were the most effective fungicides for preventing yield reduction, and vinclozolin and procymidone had little or no effect. Mancozeb and tebuconazole were effective in reducing the severity of both diseases, whereas procymidone was only active against chocolate spot. Differences between the most effective fungicides when applied 5 times or twice (at early and mid flowering) were seldom significant. Seed yields following 2 applications of tebuconazole were significantly higher than from 1 application, but for mancozeb, 2 applications were better than 1 in 1992 only. It was estimated that rust accounted for most of the yield loss in 1990 and 1992, and did so mainly by reducing seed size. Application of mancozeb early and during late flowering provided an effective and economical increase in grain yield in 1990 and 1992.