BITTER PIT IN APPLES

Colonist, Volume LVIII, Issue 14409, 10 May 1917, Page 2

BITTER PIT IN APPLES

Those who eat apples ..will frequently notice in some varieties clusters of small brown spots.'or specks-in the flesh just under the skin. These specks if not cut out have a decidedly bitter taste in the rmrath. This is the disease known to commercial applegrowers as bitter pit. Up to the present time no certain cure- has been been found for it.

Some years ago the orchardists of the Commonwealth of Australia induced the Government to appoint a plant pathologist, at a,.salary of £1,000 per annum, to be paid by the States hi proportion, to go exhaustively into the matter, with a view of finding out a remedy. For a number4 of years past Professor D. M'Alpine, the gentleman 'who received the appointment, had been conducting both field and laboratory experiments, and from time to time has issued interim reports giving details of the progress of these experiments, etc.

j In the April number of "The Fruit World" his fifth report is published hi extent. Though necessarily technical and scientific, it is nevertheless quite practical, and will form a valuable addition to .Australian works on pathology. . . As some of New Zealand's best export varieties of apples are often affected with this disease, it may interest our fruit-growing readers to know what the professor has so far learned from his many and exhaustive experiments las to what means the orchardist should adopt to prevent its occurrence.

In the previous reports the professor stated that he had come to tiie conclusion that the principal cause of the pit was: (a) Concentration of cell .sar> in the tissues of the apple, and consequent local death of the parts; (b) over pressure of "water in the tissues leading to local rupture and subsequent death of the parts.

When the fruit is mostly confined to the main nipright branches and produced on spurs, pit is usually increased. ,The strong flow of sap m the spring' I might reasonably be supposed to burst the thin walls of the pulp cells, and thus produce the effect. The "sap monies up in the spring ut'a- pressure of about 301b to the square inch. In a young and vigorous tree bearing only a few apples of rank growth, ail the fruit is often pitted. Rank 'growth /causes rapid tension of the cclf wall, and thus may reach breaking point •vvhon the pressure is distributed only through a few apples. " " This happens' also when a large tree in full bearing has only a light crop and .the apples comparatively large. Here ipit is again much in evidence. All trees of a susceptible variety undoabove conditions are prone to pit 'badly. For instance, -in a row of Cleopatras (f>9 trees) those carrying a l arge crop with apples 2in in diameter had only 1 per cent, pitted, while the trees ■ with a few large fruits 3£in in diameter had 61 per cent, affected.

Over-watering or irrigating is a sure! menus of producing pit. When apple! jtrees are so treated, and particularly! late in the sea sen, when the fruit is approaching its full development, there :is a much higher percentage of pit than ;when light watering is adopted. '' The great problem of bitter pit, like that of modern civilisation, is to strengthen the constitution of the tree ' against the forces which tend to weak-! «a it. . ■ j —To Prevent Bitter Pit. — For export purposes pick fruit ivhen I it has reached its full size, but before it is fully i-ipe. ' ! With trees liable to pit, prune lightly ;wken the bearing stage ha s been reached, having regard to the bearing! f capacity of the tree, vigour of growth" symmetrical development of its laterals.

Where irrigation is practised water fightly throughout the season; just using sufficient to keep the trees going steadily.-

Some trees that are liable to develop bitter pit: Hibston Pippin, Cox's Orange, Cleopatra, Stunner, Wellington Pippin, BaldAvin.