“…The literature on effects of soil pH on the severity of powdery scab is confusing and contradictory, as illustrated by, for example, the reported effects of adding lime to soil to make it more alkaline. Although the nature of the lime used is often unclear, Berkeley (1846), Brunchorst (1887), Horne (1911b), Pethybridge (1910Pethybridge ( , 1911aPethybridge ( , 1912, Melhus et al (1916) andEl Fahl &Calvert (1976) all claimed that liming increased disease severity, but Massee (1908Massee ( , 1915, Janchen (1921), Philipp (1932), Wenzl et al (1972), Reichard & Wenzl (1976) and Winter & Winiger (1983) associated the application of lime with a reduction in the severity of powdery scab. Sprau (1966) found that adding lime to soil had little effect on powdery scab.…”