EVALUATION OF CHEMICAL FUNGICIDES FOR CONTROL OF ONION WHITE ROT

Nine chemicals in 1976 and six in 1977 were evaluated in a five × five simple lattice design for control of Sclerotium cepivorum Berk., the causal agent of white rot of onions. The trial was conducted on organic muck soil in Burnaby, British Columbia, with uniform high levels of added (1976) or natural (1977) inoculum. The percentage of white rot infection, weight of healthy bulbs harvested and percentage of emergence were measured. There were significant differences, according to treatment, in the percentage of white rot infection of onion at harvest. Two chemicals, vinclozolin and iprodione, provided promising results as broadcast treatments on organic muck soils. A comparison of the results, in relation to differences in the distribution of inoculuin between the 1976 and 1977 trials, suggested that the major point of control may have been against mycelial growth through soil from sclerotia, remote to onion seedlings and/or from infected plants to healthy plants. Copyright © 1979 John Wiley & Sons, Ltd