DISEASES OF THE VINE.

New Zealand Journal of Agriculture, Volume XII, Issue 4, 20 April 1916, Page 282

DISEASES OF THE VINE.

PREVENTIVE AND REMEDIAL MEASURES.

A. H. MAZURE,

Vine and Wine Instructor.

The majority of the methods described below for coping with the various diseases of the vine have been thoroughly tested in all the leading wine-growing countries of the world, and can therefore be recommended with confidence. There are also some treatments which are practically new, and further experimental work will be necessary before finally deciding their respective values. It is not always a wise course to wait for the disease and then treat it. In districts where vine-diseases are known to exist, preventive measures are always the best. Most of the following treatments are based on the fact that prevention is better than cure.

VINE OIDIUM (OIDIUM TUCKERII.)

This is probably the best-known fungus disease in vine-growing, and is fortunately the most amenable to treatment. Nevertheless, it can be very troublesome, particularly in cool vinehouses. Vines attacked by oidium may be recognized by the following symptoms : The green parts become covered with a whitish dust, and after a while grey spots appear on the places attacked. Close and moist weather-conditions are favourable to the development of oidium.

Sulphur (triturated) is probably the best remedy for mildew. A new remedy described in the December issue of the Journal namely, \ permanganate of —appears to be giving excellent results in France. However, as sulphur is the standard treatment and a fairly sure remedy if applied at the right time-November, December, and Januaryit will be advisable to give some particulars of it here, and to leave the permanganate remedy until further experiments have been carried out with it. Three sulphurings at the very least should be carried out. The first two are the most important. It is absolutely necessary that the sulphur should be applied when the shoots are from 8 in. to io in. long, and also during the florescent period ; again in December, and, if necessary, again in January. The quantities to be used per acre are—for the

first application, 8 lb. to 12 lb. ; for the second, 15 lb. to 24 lb. ; and for the third, 30 lb. to 35 lb. Choose, if possible, warm calm days. Be sure to use the best sulphur, and see that it is finely ground, as this will ensure the foliage being completely covered.

BLACK-SPOT (ANTHRACNOSIS).

This disease is caused by a microscopical fungus called Sphaceloma Ampelinum. It is undoubtedly one of the worst diseases of the vine, and is very difficult to cope with. It can be readily recognized by spots or cankers appearing on the green parts of the plant. The spots are small when the disease commences, and then extend, gradually sinking into the tissues. If some preventive measure is not used the disease generally results in the total destruction of the crop and in many cases of the vine. It is very prevalent in damp muggy seasons on low soils. I have noticed in New Zealand four varieties that are particularly susceptible to black-spot —namely, Thompson’s Seedless, Golden Chasselas, Temperano, and Cabernet Sauvignon.

In districts where the disease is known to exist everything that can be done should be done to prevent a recurrence, for when started on the young growth it is extremely difficult to check-—in fact, it has been found almost impossible to then control the trouble. In planting, avoid any notably susceptible varieties of vines, and do not plant in situations which are favourable to the development of the disease.

The treatment which so far has proved most successful in France and in Australia is the following one: A io-per-cent, solution of sulphuric acid is applied to the vines in the winter as soon as possible after pruning. Use a mop made with rags tied to the end of a stick and paint the solution on to the wood. If a spraypump is used it should be lead-lined. Be sure and wet the vine all over. This will destroy a large number of spores, which would have started the disease early in the spring. An application is made, just before the florescent period, of triturated sulphur and bolted lime in the proportion of sulphur 4 parts and lime 1 part. Immediately after the florescent period a further application of sulphur 3 parts and lime 2 parts is given. A few days later another application is made in the proportion of sulphur 2 parts and lime 3 parts. This should be repeated until the disease is completely eradicated.

As black-spot is extremely - prevalent in this country the treatment just mentioned should be given a thorough trial here. It is

claimed that, although a good deal of labour is entailed in carrying it out, the treatment practically eliminates the disease for at least three years. If such is the case the cost naturally amounts to very little.

Another useful check for black-spot is Bordeaux mixture at the rate of 4-4-40, but this spray is by no means a cure, nor is it a preventive for the disease.

Spraying with lime-sulphur, 1 in 125, after the florescent period, is also a preventive, provided it is followed later by a solution of increasing strength as the growth of the vine becomes stronger. The strength of the mixture should gradually rise until 1 in 80 is reached. It is not advisable to have it higher, as otherwise the spray tends to burn the vines severely.

GRAPE-ROT (BOTRYTIS CINEREA).

Thin-skinned grapes often rot when the weather is damp and rainy at the time of ripening, and particularly so if the vineyard is in a low situation. This is due to a fungus, Botrytis cinevea. This fungus also affects the wine which is made from affected grapes, causing the disease called “ casse.” The best cure for the disease is to strip the leaves below the bunch a few days ■ before picking the grapes. This allows a. free current of air, and more heat is reflected from the soil, the action of both factors helping the' maturation’ 'of the fruit. This disease is sometimes known as grey-rot. . • ’

BLACK-ROT (PHOMA NIRCOLAE).

Black-rot is first seen on the berries as a bluish-red J spot, which increases in size and eventually surrounds the. whole fruit. After this stage it becomes red-brown and soft, and the berries will dry in three or four days, the colour becoming nearly black and the skin adhering to the. pips, while the whole surface is covered with small prominent brown spots. These latter make their first appearance when the fruit is gradually drying.

The disease appears to develop easily in low and very damp situations, particularly with varieties of grapes of a very juicy nature. The best means of coping with this trouble is to spray with Bordeaux mixture, 3-3-50, taking care that the spray thoroughly covers the vine. If the mixture is applied four or five times in the season the disease will be entirely overcome.

(to be continued.)