ORCHARD AND VINEYARD

New Zealand Journal of Agriculture, Volume 71, Issue 4, 15 October 1945, Page 413

ORCHARD AND VINEYARD

Spraying, Cultivation, and Thinning

THE effective control of pests and diseases will be the chief concern of orchardists for the next two or three months. The general spraying . programme for the season in last month’s notes should be adhered to. The . stage of growth is very important in spray . applications, and the necessity of . applying the correct material at. the right , time cannot be too strongly emphasised. In some localities the blossoming period of most apple and pear varieties will be well advanced, and most of the trees will now be ready for the petal-fall sprays recommended in last month’s notes. The petal-fall or calyx stage is a critical period, as black spot and powdery mildew almost invariably make an appearance at this time of ' the year. It is quite safe to spray when 75 per cent, of the petals have fallen, as the function of the blossom and the process of pollination will have been completed by this time. The fruit-set stage is also ’ a critical time, and careful attention must be given if . the best, results are to be obtained. The spraying of pears with Bordeaux mixture, at a strength of 3-4-50 should be continued, particularly■ on varieties, such .as Winter . Nelis, susceptible to black spot... The continued spraying of peaches and nectarines is necessary for the

control of brown rot and leaf rust. Lime sulphur 1-200 plus colloidal sulphur 21b. to 100 gallons should be applied at intervals of three to four weeks. These summer applications are frequently .withheld and invariably defoliation occurs as a result of leaf rust. Where black aphis is present on Japanese plums, spraying with summer oil 1-100 is recommended as a control, concentrating on any dense colonies which may be observed. Cultivation The cultivation of the orchard should continue to receive attention. The soil should be . worked down to a fine tilth and kept well stirred to a depth of from 3in. to 4in. to conserve soil moisture and to allow of the free access of air to the rooting system. How frequently the orchard should be cultivated will depend largely upon weather conditions. The soil should be worked as soon as possible after heavy rains to prevent the formation of a heavy crust. Cultivation should be as close as possible to the trees and any remaining herbage should be removed by hoeing or digging. Poor cultivation or lack of cultivation is usually reflected in the condition of the trees and poor quality of the foliage.

Fruit Thinning One of the most important factors in successful fruit growing is fruit thinning. With the present shortage of labour this work is frequently neglected, with the result that, under droughty Conditions, a certain amount of fruit has to be rejected because it has not reached marketable size. The weight of fruit harvested from a wellthinned tree is frequently greater than from a tree which is allowed to mature the whole of its crop, as the remaining fruits attain a larger size and usually are of better 1 quality. Where there is only a limited time for thinning and it is not possible to do the whole orchard, varieties such as Gravenstein, Cox’s Orange, Dunns, Sturmer, and Dougherty should receive preference. By careful thinning diseased and blemished fruits may be removed, uniformity in size may be secured, and the resultant crop would be .of much more value and less costly to handle. The tree will benefit by thinning of the fruit, as the maturing of a well-thinned and distributed crop is less exhausting, which is reflected in the quality of the foliage and growth. The extent to which thinning should be carried out must be gauged by the crop. It is more often inadequate than overdone. . Thinning should commence as soon as the natural dropping has taken place and when there is no further danger of late spring frosts. Some growers prefer to thin by hand, but the use of special thinning shears is recommended, as when thinning, is done with the fingers the remaining fruit is often loosened, particularly with short-stemmed varieties, . with the result that it soon falls. J. HOGG, Orchard Instructor, Mapua.

Citrus Notes

Cultivation and Pest Control

nr’HE setting of the citrus crop can THE setting of the citrus adversely be, and often is, adversely affected by cultivating too deeply, especially during November and December, when most citrus trees will be at the fruit-setting stage. Any cultivation during this period, either by hand or by machine, should be sufficiently shallow to avoid damage to the roots. With oranges, and to a smaller extent with other kinds of citrus, there are two distinct periods when the trees shed a percentage of the young fruits;. the first is during the fortnight following petal-fall, and the second is usually about the third

week in December, extending in some seasons to the end of December or early in January. Any injury to the roots during these periods is certain to cause an increased dropping of young fruits. • The conservation of soil moisture is probably of greater importance at this period of the year than at any other. The cultivation of the surface soil in itself has little beneficial effect in this direction, but it is extremely important that weed growth should not be permitted to compete with the trees for the available soil moisture during the critical fruit-setting period. The loss of moisture from the soil by evaporation is greatly increased when the surface is left uneven, as frequently occurs after discing or ploughing. In such cases it will greatly assist in soil moisture conservation to harrow or roll the surface soil as early as possible after the normal cultivation has been completed. In pasture orchards the soil moisture is mainly lost by transpiration through the leaves of the pasture and

the trees; this loss will be greatly reduced by frequent mowings, even when the pasture is only a few inches high. Pasture mown at this period of the year should be allowed to lie where it falls and not placed around the trees as a mulch, excepting perhaps in the case of very young trees. Scale Insects The presence of olive (or black) scale on citrus trees is generally indicated by the development of a conspicuous sooty-mould fungus on the foliage and fruit. Where the. infestation is light a satisfactory control of this pest can be secured by adding 1 per cent, or 1| per cent, of a certified brand of summer spraying oil to one or more of the Bordeaux sprays applied for the control of verrucosis. Hemispherical (or brown) scale can be similarly controlled. Should there be considerable infestation of these scale insects, a separate oil spray should be applied at a strength of 2 per cent. In orchards , where red scale is also present the strength

should be increased to 3 'per cent., but if red scale only is troublesome, better control will be z secured by making the application in February., Harvesting Oranges and grapefruit should be harvested as rapidly as the fruit reaches a suitable condition, and this should be continued at intervals of from 2 to 3 weeks. There is a definite danger of loss of juice from mature fruits allowed to remain on the trees too long, especially during November and December. Furthermore, the . appreciable quantity of nutrient sap utilised by the tree in keeping the mature fruits in a fresh condition greatly reduces the ability of the tree to set the next season’s crop, thereby accentuating the drop of young fruits in December. Borer Control The larva of the long-horn beetle (Aemona hirta) is one of the most destructive pests of mature citrus trees. The pest becomes progressively more difficult to control as the trees mature. The presence of borer is detected by the wood dust ejected from the tunnels in the larger limbs, also by wilting of the smaller branches. Very frequently the larvae enter the tree in the first, place through a dead twig or wound; consequently the frequent removal of . dead twigs and the coating of wounds caused by broken limbs or in the course of pruning with a heavy grade of petroleum jelly will prevent infection to a considerable extent. Infected branches up to about lin. in diameter should be cut off and destroyed. In the larger limbs the wood dust should be first cleared from the holes as far as possible and a fine wire inserted to kill the borer. Benzine or carbon disulphide is then injected into the holes, after which the holes must be immediately plugged with petroleum jelly or other suitable material to prevent the fumes escaping. Excessive use of these liquids should be avoided, otherwise injury to the wood may be caused. Pruning Pruning should be completed as early as possible, especially where a heavy or severe pruning is being undertaken. If for any reason such pruning cannot be completed by about the end of October, it is advisable to modify it in the remainder 'of the orchard. —P. EVERETT, Orchard Instructor, Kaikohe. “The Citrus-growing Industry: How to Establish an Orchard,” Bulletin 206, is available free from offices of the Department of Agriculture.

Bees and Orchard Sprays WHILE most other species of pollinating insects are erratic in their visits, and usually make long flights from one type of flower to another, feeding only to satisfy their own appetites, the honey bee goes about her work in a systematic order, visiting the flowers of one kind of tree in rapid succession. This characteristic has tremendously , popularised the use of bees in commercial orchards, as cross-pollination is essential in most fruits and desirable even with self-fertile varieties. Though the service rendered to orchardists by bees is inestimable, complications arise with the necessity to control orchard pests, and orchardists who continue to spray with arsenate of lead when their trees are in full bloom threaten to poison the bee population in commercial orchard areas. Experimental work carried out by officers of the Department of Agriculture, in co-operation with leading orchardists, has shown ' conclusively that fullyefficient control of codling moth is obtained by the withholding of arsenate sprays until after petal fall. Although the emergence of the codling moth coincides approximately with the latter part of the blossoming period, the early infection of moth is mainly through the calyx, which necessitates the application of an arsenate of lead spray before the calyx closes. The period of approximately 8 to 10 days between the falling of the petals and the closing of the calyx is long enough to enable a spray to be effectively applied against early infection by the moth. The grower can readily determine this period, and no benefit .is obtained by applying sprays as a control of codling moth before the petal-fall stage, or when approximately 75 per cent, of the petals have fallen. During full bloom bees have free access to the blossoms containing the flower parts essential for fertilisation. When those : parts wither after having • fulfilled their purpose and, with the falling of the petals and the end of nectar secretion, the attraction for bees ceases, spraying with arsenate of lead can be commenced in good time for effective control of codling moth, with the minimum of danger to bees. Bees would be further safeguarded if all growth about the trees holding spray drops were turned in and plenty of fresh water made available in apiaries, so that bees would have no necessity to take up poisoned dew drops resting on vegetation under trees to get the water needed for brood-rearing.