APPLE AND PEAR SCAB.

New Zealand Herald, Volume LXIII, Issue 19217, 5 January 1926, Page 12

APPLE AND PEAR SCAB.

TREATMENT OF DISEASE. VALUE OF WINTER SPRAYING. Although the fungi causing scab on apples and pears are different, they are very closely allied; but as the general appearance of the disease and the methods of treatment in each case are identical, separate descriptions arc not necessary. Scab is probably the mose general and most widely distributed of fungus diseases attacking apples and pears, and during certain seasons the entire crop is much depreciated in value, or rendered altogether unsaleable, owing to the presence of numerous blackish blotches or scabs and gaping cracks on the surface. To the casual observer scab is only recognised on the frpit, whereas in reality the fungus appears first on the leaves and young shoots, whence the spores are washed by rain on to the fruit, which is the last to be attacked. If the fruit is nearly fullgrown before it is infected the spots formed by the fungus remain small and are ftregularly scattered over the surface. Although the market value is thereby depreciated, such fruit is not materially injured, the scabs being quite superficial. If, however, infection occurs when the fruit is young, its further growth is checked; the surface becomes more or less covered with scabs of various sizes, and at a later stage is irregularly cracked. On the leaves and young shoots the fungus forms minutely velvety, dark-coloured patches which have an olive-gieen tint when the spores are ripe.

Treatment. —(1). Spraying with halfstrength Bordeaux mixture (i.e., 61b. of copper sulphate and 31b. of quicklime to 100 gallons of wa.ter), should be commenced on tlie first appearance of the fungus on the foliage; if spores are once allowed to mature the case is practically hopeless, owing to their enormous numbers and rapid dispersion. The spraying should be done at intervals as found necessary until the .apples are about the size of a Hazel-nufc.. Strong Bordeaux mixture must not be used, otherwise the faliage will bo scorched. (2). When the dis.ease has been present in an orchard all apple and pear trees should be thoroughly drenched with a solution of sulphate of copper—lib. of the sulphate to 25 gallons of water. This should be applied during the winter, before the buds begin to swell, otherwise the foliage will be completely destroyed. This winter wash is of great value. in destroying fungus spoires present in crevices in the bark, and should be regularly applied as a preventive. (3). The fungus tides over the winter in fallen diseasd fruit* All such fruit should therefore,be gathered and burned.