Factors determining the efficacy of chemical control of white mold in white bean

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Abstract
The effects of volume, timing and number of sprays of benomyl, and arrangement of nozzles on the efficacy of chemical control of white mold [Sclerotinia sclerotiorum] of white bean (Phaseolus vulgaris) were determined in five trials. The greatest suppression of disease and the greatest increases in seed yield were obtained when fungicide was applied at full bloom at a dose of 1.1 kg a.i./ ha in 550 L water/ ha through three flat-fan nozzles per row, one nozzle on a horizontal boom above the row to direct spray downward and one on each side of the row and held by skid booms 8 cm above the soil surface to direct spray at the base of the plants. Disease control was less effective when the volume of spray was reduced from 550 L/ ha to 243 L/ ha and when nozzles were arranged on a horizontal boom and drop arms or on a horizontal boom only. The level of disease control did not depend on the time of spraying during flowering but was directly related to the number of blossoms within the canopy that received fungicide.