Abstract
SUMMARY: Using phenylmercuric chloride (PMC) as the experimental fungicide it has been shown that spraying trees once in autumn at 0.05% and again just before bud‐burst at 0.01% reduced scab infection on blossom truss leaves by over 99% in the following spring. In another orchard 0.01% PMC sprays in autumn and just before bud‐burst, followed by fungicide sprays in spring and early summer, gave complete control of scab. In a third orchard, which was subject to contamination by ascospores from non‐treated apple trees, infection was reduced by 56.9% by one autumn and one pre‐bud‐burst spray of 0.01% PMC without subsequent anti‐scab sprays.