Scab, Canker, and Branch Blister of Apple at East Malling in Relation to Nutritional Treatment of the Host

Abstract

On the sandy loam at East Mailing, moderate annual dressings of inorganic sources of nitrogen and potash exerted no consistent influence on the incidence of apple scab, even when the dressings were continued over an eleven‐year period on established trees of four different varieties on M.IX rootstock. Likewise, no influence of such dressings continued over five seasons was shown on the incidence of apple canker on the rootstock M.VIII, which was grown under conditions favourable for severe infection.There was evidence from early observations that grassing‐down to excess can reduce the incidence of scab, but only at the expense of nitrogen starvation in the trees. Short‐term mixed leys had no such effect.The incidence of branch blister, a functional disease associated with adverse soil conditions and retarded vigour, was greatly reduced in the variety Cox's Orange Pippin by potash manuring, and was further influenced by the rootstock.

Apple Rootstocks Susceptible to Scab, Mildew and Canker for Use in Glasshouse and Field Experiments

“…Infection of the upper leaf-surface was recorded on each plant in blocks 1 and 2 in September 1951, Where possible, the topmost ten leaves of ten random shoots were sampled, and the area of infection was graded into four categories-<h <h <h > 2 surface covered. The results, expressed as mean index of scab severity per plant (Moore, 1952), showed the following gradation: The four most heavily-infected stocks on each occasion were XVL VIII, III, and II, but there were inconsistencies. For example, the late-leafing XVI, most heavily infected in 1951, escaped primary infection in 1959 through absence of foliage during a severe infection period when most of the other stocks were between the mouse-ear and green-cluster stages.…”

“…(Moore, 1947). Mailing III and M. VIII have already proved particularly useful for intensive field experiments (Moore, 1952;Moore and Bennett, 1952;1960), but, as neither is commercially desirable for fruit trees, regular supplies must be specially grown. The relative susceptibility of the readily available stocks was not known, and this information may not be forthcoming from general nursery practice because normal husbandry and annual harvesting, by removing a major source of infection, usually preclude epidemics.…”

“…There were inconsistencies not only from one season to another but also between sites, notably with M. IV. M. VIII has already been used in several canker experiments (Moore and Bennett, 1952;1960).…”

“…The incidence of disease among varieties in the field is not necessarily a reliable criterion in glasshouse experiments. M. Ill, for instance, readily infected by scab ascospores from Bramley's Seedling leaves in the field (Moore, 1952), was an obvious first choice for infection experiments on potted rootstocks under glass, yet it consistently showed fleck reaction to ascospores from another Bramley source (Plate III, 1). On the basis of their field record, therefore, M. II, III, VIII, XVI, MM.…”

The control of apple canker (Nectria galligena) in a young orchard with established infections

“…In August 1974 nine trees were found to be dead or dying as a result of infections on the rootstock. These lesions apparently originated at burrknots (Moore & Bennett, 1952). The hare guards probably maintained a humid atmosphere suitable for infection and although uncommon on branch cankers numerous perithecia formed on the rootstock lesions.…”