Effect of Starting Date and Number of Sprays on Apple Scab Control

Summary When, after adequate spraying in previous years, the level of inoculum was fairly low and there were few infection periods (in the dry seasons 1963–64), good fruit‐scab control on cv. Laxton's Superb was achieved with six protective high‐volume dodine sprays, applied fortnightly between †bud‐burst and fruitlet stage. With increasing inoculum control worsened: eight sprays from bud‐burst were needed for a satisfactory result in 1965 and nine were barely adequate in 1966, the wettest season of the four. By 1964 it already seemed that delaying the first applications until green‐cluster made spraying into July (six applications) desirable, and starting later than bud‐burst in 1965–66 gave inadequate control, even if six or seven sprays were applied. Thus, where conditions favour scab, protective spraying should always start at bud‐burst. If scab is difficult to find at fruitlet stage, spraying need not be continued beyond that stage.