RIPE-ROT OF STONE-FRUITS.

New Zealand Journal of Agriculture, Volume XII, Issue 3, 20 March 1916, Page 214

RIPE-ROT OF STONE-FRUITS.

A. BAILEY MANSFIELD,

Orchard Instructor, Auckland.

Quite a number of peaches and nectarines affected with ripe-rot were sent in to the Department’s Auckland office for examination during, the latter portion of January and through the month of February. In most of the Auckland peach-growing districts the loss of fruit from ripe-rot has been considerable. Ripe and partially ripe fruits of the peach and nectarine affected by this disease show a yellowish covering of dust-like powder mixed

with a bluish tint. If observed in an earlier stage the area affected will be whitish instead of bluish; later the whole fruit becomes either a rotten mass or small and shrivelled, and the powdery substance occupies a larger area. The rotting of the fruit is caused by a fungus (Monilia fructigena') allied to the com-' mon blue mould which forms upon bread, and the powdery mass *ln New Zealand this disease is frequently termed brown-rot.” More correctly, however, and for the sake of distinction, the latter name should be confined to a similar disease of the apple and other pip-fruits.

is composed of spores. The white coatirg upon the fruit is the mycelium, the vegetative' part which bears the same relation to the fungus that, the roots do to a higher plant. The mycelium grows into and through the tissue of the fruit, and after development the fungus spores are formed. These ' are ' visible as the bluish powder or mould. The spores, which are thin-walled and oval in outline, are joined together in bead-like strings, and as they become matured break off, blow away, and fall upon the fruit. Given the ■ right climatic conditions they start to grow rapidly. A slender tube is sent out, continues to lengthen, and, finding entrance into the fruit, it grows and develops, and spores are ’ again produced. The disease frequently gains access to the fruit through a puncture in the skin—even a bruise is sufficient. ■ Usually it is first seen in peaches or nectarines that are in direct' contact with each other, and it spreads most rapidly during moist* warm weather.

Although most of 1 the commercial fruitgrowers recognize this form of fungus and are aware of its destructiveness, yet few are familiar with its history. After a season when ripe - rot has been bad a serious reinfection may be expected the following spring, because the disease is carried over in the mummied fruit left on the trees,

or by infected fruits and leaves

under the trees. Little can be

done to cure the disease, but much good can be accomplished preventively by spraying with lime-sulphur solution in the early summer and whilst the fruit is developing on the tree. This, will prevent infection of fruits not already affected. Lime-sulphur may be used in the proportion ,of i part of lime-sulphur solution to ioo to 125 parts of water. In the winter the trees should be thoroughly sprayed with sulphate of copper (pure bluestone)' in the proportion of 1 lb. of bluestone to 10 gallons of water.. The early spring spraying with either lime-sulphur solution or Bordeaux mixture should not be neglected. In pruning the trees all mummied fruits should be cut off.

When marketing the, fruit during the season, care should be exercised in picking to avoid bruising and puncturing the skin, as the disease will develop during transportation to the markets. Quite a lot of fruit has arrived on the market • affected with • riperot. Care should also ‘be taken in the packing-house to remove all diseased fruit, 1 otherwise the spores may find lodgment in the building and continue to affect every load'brought into it. Thorough' ventilation will assist materially in checking the spread of ' the disease. Cull fruit should ' not be allowed to remain about to decay, but should be destroyed, preferably by burning. ' c ...