CULTIVATION OF THE VINE UNDER GLASS.

New Zealand Journal of Agriculture, Volume VI, Issue 2, 15 February 1913, Page 156

CULTIVATION OF THE VINE UNDER GLASS.

(Concluded.)

S. F. Anderson.

Pests of the Vine. The most common and worst pest known to the grower of vines under glass in this Dominion is the Mealy-bug (Dactylopius adonidum). This belongs to the order Coccidae or scale insects. Quoting from leaflet No. 21 (T. W. Kirk, F.L.S.) : “ This insect is common throughout the world, and in warmer portions of the globe frequently causes extensive damage, especially to grape-vines under glass. The common name ‘ mealy-bug ’ is given because the insects (female) are more

or less covered with a yellowish-white mealy-looking powder which they throw out from, their bodies, the object being principally to provide protection from enemies, but it also serves to conceal their eggs. The mealy-bug when full-grown is about | in. long, being in colour white tinged with yellow, and a brown band on neck. The margins of the body are armed with a number of spines, and there are two long cottony threads extending backwards from the last segment of the abdomen. Mealy-bugs are dreaded on account of the enormous rate at which they multiply, a single female laying several hundred eggs a day.” Methods of Distribution. /Without doubt birds play a very important part in the distribution of scale insects by carrying them on their feet and legs. The young mealy-bugs are very small, and might easily be carried from their footing by a strong gust of wind and deposited some distance away. When once this insect gets into a vinery very rarely is this entirely cleared of it. Very few growers, indeed, claim to have done so. The bark of the vine, woodwork of the house, and the soil at the base of the plant afford cover for the eggs. Prevention is what must be looked to by those going in for vine-culture under glass. See that the vine-house is placed away from trees, shrubs, and hedges. Do not allow any pot-plants or creepers of any kind to be put in the vine-house. The raising of seedling plants in the vine-house, provided the boxes used are clean, may be done. Where the work of the vinehouse is conducted in a methodical manner, and not too large an area is placed under the care of one man, every part comes under attention so often that: the presence of any pest can or should be detected. When found it should be treated at once, and a search made for others. It has been found on the foliage at the top of the house and on no other part of the vines, proving that it can be carried by the wind.

Treatment of the Vines when the Insect has become lodged in the House. When first discovered a small bottle of methylated spirit and brush should be kept, and diligent search made for the insect and eggs, and when found touched with the spirit. This destroys both effectively. Should, however, the mealy-bug have obtained too extensive a hold to be controlled by the above treatment, the vine-house must be fumigated with the hydrocyanic-acid gas. Before attempting to use this remedy the operator must realize that he is dealing with a very deadly gas, one or two full breaths of which would probably be sufficient to cause death. With proper precautions, however, there should be no danger in its use either to plant or man. The following directions should be carefully followed :

Time of Day to fumigate. — Fumigate in the evening between sunset and dark. Strong light induces injury to foliage. Choose an

evening when the atmosphere is still. Never fumigate during a high wind.

Condition of Foliage and Fruit. Do not fumigate vines in the early spring when the foliage is very tender. The fruit should be as large as small marbles, and the shoots should have hardened before the first fumigation. The plants and top soil should be dry; moisture absorbs the gas and renders the atmosphere less poisonous to insect-life. Moisture on the foliage will take up the • gas, and, acting as a . diluted acid, cause extensive burning of the leaves.

Fumigating-material. The cyanide to be used must be 98 per cent, pure; lower percentages have occasioned severe burning. For every 100 cubic feet of space in the house use | oz. by avoirdupois weight of cyanide of potassium, | oz. by measure of commercial sulphuric acid of 1-813 specific gravity, 1 oz. of water by measure.

Method of applying the Chemicals.— Provide earthenware basins that will hold from 6 to 12 quarts according to size of house to be fumigated — basin for every 10 ft. of the house. Divide the quantity of the chemicals by the number of basins, then place the water and sulphuric acid in the basins and put them in position. . Weigh out the cyanide into pieces of paper or saucers and place one at the side of each basin. The cyanide may want breaking up into pieces; it should not be in lumps larger than a filbert nut. When, all is ready and all openings closed excepting the door, commence at the far end and put the cyanide into the acid and water, taking care to keep the head away from the gas arising, and work backward and out of the door. When this is accomplished close the door and leave the fumes in one hour. When fumigating in the dormant —viz., when the leaves are falling gas may remain all night. The doors and ventilators should be thrown open at the end of the hour and nobody permitted to enter the house for thirty minutes, and then with caution if the gas can be noticed. .

Caution. When breaking up or handling the cyanide on a warm evening with the hands perspiring, the hands should be washed immediately on finishing. If the quantity to be prepared is large, the hands should be . washed more than once and the mouth washed out with water. In handling' the sulphuric acid it should be poured into the vessels without splashing, as it will burn the hands if these come in contact with it. , ■

Example of calculating the Cubic Contents of a House for the Quantity of Chemicals required. Assuming the size of the -house is 51 ft. long,

16. ft. wide, sides 3 ft. high, and the pitch of the roof 40°, the cubic content will then be, — ' Cub. ft. Body of house, 51 ft. by 16 ft. by 3 ft. .. .. 2,448 Content of roof: Draw a line across the house from top plate to top plate, and from that a vertical line to apex of roof. This will be about 7 ft. 9 in. ■ Take the half of this and call it 4 ft. Then multiply the square of the house by —viz., 51 by 16 by 4. This equals .. .. .. .. .. 264 Total cubic contents then equals .. .. 5,712 Quantity of Chemicals required. We may call the space 5,700 cubic feet. Then, as the calculation is per 100 cubic feet, the quantity of cyanide of potassium will be 57 x | = 19 oz. ; sulphuric acid, 57 x|= 19 oz. ; water, 57 oz. This divided amongst five basins will give 3| oz. each of the cyanide and sulphuric acid and Ilf oz. of water to each basin. , ~ j

The fumigation does not, however, destroy the eggs, ,so it may be that a second fumigation will be necessary. This should be done just as the berries are beginning to colour. After the fruit has been

gathered, and when slight injury to the foliage would not matter, a third fumigation, a little stronger, should be given. If the first has been found effective the second might be omitted. ' ’ .

The winter treatment of the vine -has very much to do with success in freeing it from pests. If this work has to be summed up in one word it would be “ cleanliness.” Cleanliness is as essential in plant as in domestic houses. As soon as the leaves fall, the pruning is completed, and the house cleared of all rubbish — vine-rods should have all the loose bark removed, but only that which can be easily

rubbed oil with a bit of sacking or coarse glove. There should be no scraping when doing this. Keep a good lookout for any deposit of mealy-bug eggs/ . These are. easily detected by the white patch of cottony material, and should at once be destroyed by touching with methylated spirit. It would be well when rubbing off the loose bark to .have old newspapers spread under the vines to catch the rubbish. When the work has been finished these can be burned, so that eggs that escape notice may be caught and destroyed. When this has been done the house should be washed down with hot water if possible. If this cannot be obtained use cold with a good pressure behind it, but the vine-rods should have the water hot. No harm will come from this, and no insects or eggs can stand it. The vine-rods should now be painted with the following: Get a quantity of good plastic clay and dry it thoroughly, then powder it up so that it can pass through a in. sieve measure off with a 6 in. flower-pot nine potsful of the dry sifted clay, and mix thoroughly through it one flower-potful of coal-tar. Place in a small tub and bring up to the consistency of paint with hot water, and keep well stirred while in use. Put on with a stiff brush, taking care not to scrub the buds, but just dab round them. When the rods have dried they may require looking over again, and any part that has been missed can then be treated. This clay and tar mixture has given excellent results. A word of caution is necessary here. It must be made with a good plastic clay. Ordinary soil or any containing too much sand or soil will not do. Should the proper clay not be obtainable, use a mixture of 8 oz. of Gishurst’s compound to a gallon of water, with clay added to give it the consistency of paint, and apply with a brush. . Another good paint for this purpose is made as follows : 4 oz. soft-soap, 4 oz. nicotine, 4 oz. Little’s sheep-dip, 2 oz. turpentine, and add sufficient. sulphur to form a thick cream. Dissolve the soft-soap in hot water, then stir in the other ingredients and make up to 1 gallon of the mixture. Apply with a brush. Mildew. The next most serious pest is the mildew (Oidium Tuckerii). The spores of this disease seem to be always present, only requiring the conditions favourable to development to be seen on the under-side of the leaves in small round ' grey patches, which can be detected more clearly when held up to the light. It spreads to the young fruit and growing tips with astonishing rapidity. Like almost all of our fungoid diseases, if the grower waits until he can see it much injury may have been done. Prevention, then,'- is most important in order to keep the house free. As soon as the vines have started into growth dust lightly but thoroughly with sulphur on a cloudy day when the house is cool and the foliage dry. Three or more dressings will be

required during the season. The earlier ones are the most important. Sulphuring the vines should never be omitted. Red Spider (Bryobia pratensis). . This tiny sucking insect is capable of doing considerable mischief if allowed to multiply. When, numerous its presence will be indicated by the brown or rusty appearance of the foliage. Examination of the under-sides of the leaves will show the pest in various stages- of existence. Usually along the midribs the brown- to red-coloured eggs as well as the adult spiders will' be seen. This insect may always be expected to make its. appearance during dry seasons or in houses that are allowed to become too dry. When a daily syringing of the foliage is carried out, as recommended under the head of “ Syringing the Vine,” the chances are that it may never make its appearance, as - it dors not like moisture. ' .

Thrip (Thrips minutissima).

This insect is . also found in the vine-houses of the Domini om The same conditions that favour red spider also encourage thrip. These are not easily seen,, and may disfigure the fruit a good deal before being noticed, particularly that of the late kinds, such as Gros Colman. If the house is regularly syringed these insects do not often get a firm hold. >

Scalding op the Leaves.

This is a very common, trouble in the cultivation of vines under glass in the Dominion. It may also occur on the fruit.' It is due to. improper ventilation. A delay in opening the ventilators on a summer’s morning and a hot Sun coming on the moisture-laden leaves is the chief cause. When spraying the vines in the afternoon the top ventilators should be open to permit free circulation of the air to dry the vines again. It has been already stated under the head of “ Ventilation” that there should always be some circulation of air, and where this is attended to the chances of scalding are greatly reduced. Overcropping. Overcropping is the cause of much of the trouble met with by the vinegrower. It weakens the vine by giving it too much to do. ■ The fruit cannot colour properly, and the effect it has on future crops for several seasons is very marked. Weakening a plant by overbearing is much more far-reaching in its effects than many vinegrowers suppose. It has somewhat the same effect as over-defoliating, which may be described as a slow starvation of the plant. To obtain fruit perfect in colour and size should be the aim of every grower, and it. is possible to do this every year if the foundation of the plant is well established and careful culture maintained, in after-years.