BITTER PIT IN APPLES

Nelson Evening Mail, Volume LXI, 9 June 1927, Page 2

BITTER PIT IN APPLES

RESEARCH WORK IN ENGLAND

PRUNING AND MOISTURE

The appearance of apples affected with bitter pit is familiar to those eng.aged in the, growing and marketing of apples. The flesh of the diseased apple ghqws'> small Mtema'\ spots* wbicfa. ,«.« usually most. nunieraosi' j«w>t uadfe.- ffaa\ skia... Who;:, viewed .through-tuti. slm., lliey appear as small depressions of a brown or brownish-green' colour. The brown spots are dry and spongy, and microscopic examination shows tliem to be composed of collapsed cells. These spots are hitler lo (he taste, hence the name, "bitter pit." The disease has a. very long record and a wide geographical distribution, for it. occurs in most countries where apples are grown, though it is, perhaps, worse, in the countries with, hot summers—such as America, Australia, mid South Africa—than in England. In a report, No. 28, issued by the Food■ Investigation Board, a review of the. problem is set out in some, detail, and all the available knowledge brought up to date.

Research workers appear to be satislied I hat the brown and sunken spots consist of dry anil spongy dead cells, hut they are at a loss to explain how the cells were killed or whv they should have died, for no bacterium or fungal organism has ever been found. It has been suggested by some, workers that bitter pit is due to slow local poisoning of the. affected tissue. Others have suggested that poisonous spray material,' such as lead arsenate or copper sulphate are responsible for the toxic effects, but there has been no difficulty in showing that the latter theory is unsound, for hitler pit ocelli's in "apples that have not been sprayed. The dry spongy appearance of the, spots* has suggested to some -workers that desiccation rather than poisoning may have been the cause of death; but here again the theory does not fit in with the facts, for the' bitter pit is more plentiful when abundant rainfall comes toward the second half of the growing season. Latterly, Dr. Kidd and Dr. West, because of' the similarity in appearance, between bitter pit and certain forms of artificially produced brown heart, have suggested that the two diseases may have similar causes—an accumulation of carbon dioxide inside the cells of the apple. All these theories are explained in the report, which also contains a critical examination of each one. It is pointed out that in no case has direct experiment been obtained, or, in most instances, even sought for, while on theoretical grounds, most of the theories are open to grave objection. A- survey of the published data regarding the influence of orchard factors yields two fairly definite results; that 'severe pruning "on the one .hand, and heavy water supply toward the end of the season on the other, are circumstances predisposing to bitter pit. In certain varieties bitter pit makes its appearance while the fruit is on the tree, but in others it seems prevented from so doing, although it may develop rapidly after picking. In the latter case it has been found to develop in storage to a greater extent in fruit which has been gathered in a relatively immature condition than in fruit allowed to ripen on the tree. -Where bitter pit is prevalent, growers are warned not to prune their trees severely and to leave the apples on the tree to ripen thoroughly. _- '■ |