THE HOME ORCHARD

New Zealand Journal of Agriculture, Volume 68, Issue 5, 15 May 1944, Page 351

THE HOME ORCHARD

Combating the Common Insect Pests and Fungus Blights

-ByThe Horticulture Division

THIS article is published in response to numerous inquiries from the occupiers of the smaller farm and suburban orchards. The directions are given in an elementary form to suit the special requirements for the control of codling-moth, scale insects, woolly aphis, red mite, black-spot of apples and pears, powdery mildew of apple trees, and peach-curl in such orchards. The accepted method of dealing effectively with these orchard pests and diseases is that of spraying, different

sprays being used as required. For instance, the codling-moth grub, which directly feeds upon the fruit, is destroyed by keeping the fruit covered with a film of arsenate of lead during the few months when this pest is active. It has been found that this specific renders the skin, when eaten, toxic to the insect, which is thus destroyed. On the other hand, scale insects, woolly aphis, and red mite feed upon the juices of the fruit, stem, and foliage by means of a beak which penetrates the surface * and sucks up the natural juices of the plant. For such pests, it will readily be . seen, arsenate of lead would be useless as a remedy. The present method is to destroy them with , a contact spray, which is effective as soon as they receive a coating of the mixture, this being generally of a caustic or oily nature. Black-spot on the apple and pear is a blemish of the surface of the fruit, which is not due to insects at

all, but a parasitic fungus, for the prevention of which a different spray, again, must be used. During the period of the . year when this blight is prevalent it is customary to cover the surface of the fruit tree with a spray, which prevents the almost invisible spores of the fungus from germinating and establishing themselves in the fruit or leaves. POWDERY MILDEW. Powdery mildew attacks the leaves, shoots, blossom buds, and also causes a web-like russet on affected fruits. On the foliage it appears as greyish, cob-webby patches, giving the affected areas the appearance of having been dusted with flour. The affected shoots take on a white, glistening appearance, become bare of foliage, and ultimately die. Infected blossom buds become covered with a greyish-coloured mycelium of the fungus. The diseased blossom bud clusters are usually smaller in size than the healthy clusters and rarely set fruit. The early spring prior to the “petalfall” stage of the flower is the appro-

priate period to apply sprays for the control of this disease. Sulphur sprays, such as lime-sulphur and colloidal sulphur, are the specifics recommended to keep this disease in check. Money and time are often spent on spraying- without obtaining the expected results. This is because it is not properly performed. A few points which will make for effective work are given here. SPRAY-PUMPS. The effective spraying ,of the home orchard requires a pump in good order. For a few trees the well-known bucket pump is quite suitable, but it should be clean, and the packing and unions tight. The small length of hose usually supplied with the pump is unsuitable for orchard spraying. ~ Eight feet of good -|in. hose and a 4ft. directing-rod improve the outfit very much. ■ To do good work requires one person to carry the bucket of spray and pump and another to apply the spray to the trees. This operation must be done thoroughly and systematically, for most of the pests and diseases shelter in the angles of twigs, under the leaves, and in abrasions of the bark of the tree. Commence at the

top and . work downwards giving as much attention to the inside of the trees as is given to the outside parts. Consider the windage, and work in dull weather or afternoons if possible. For larger areas a barrel pump is more suitable than the bucket pump. ATTENTION TO DETAILS. Another important point affecting results ’is the preparation of sprays. Buckets used for oil should not be used for bordeaux mixture or limesulphur without being washed, or vice versa; it is a good plan to keep separate vessels for the purpose. Weighing and measuring of ingredients must be accurate. A little too much or too little may burn the trees and cause loss of the crop. When mixing have a batten handy to stir the mixture well, and again occasionally, while applying it, so as to prevent any settlement of the ingredients. SPRAY AT RIGHT TIME. To be effective sprays must be applied at the right time. Codling-grubs are feeding in November, and are about until February and March, the period varying slightly with locality. Scale insects are dealt with at almost any time, but are more easily destroyed in early spring just before their eggs begin to hatch. Woolly aphis is most dangerous in autumn, when winged emigrants appear, which establish new colonies.

Red-mite eggs, which are often found about the base of leaves . and twigs, hatch in early spring, and egg-laying is active about the month of March in such places; effective work can be: done by spraying at these times. Black-; spot spores issue in early spring from the fungus wintering on leaves and branches, and settling on the leaves and fruit, under suitable conditions, make root-like growth which penetrate the tissues of the. host. Usually the most dangerous period is during September, October, and November. Powdery . mildew spores become' active early in the spring at the time the buds are swelling. Suitable measures taken during September, October, November, and December will do much to control this trouble. These facts are given to show the importance of ■ spraying at the time mentioned in the directions which follow—. - - - - - - CODLING-MOTH. Considerable loss results each season from the depredations of codlingmoth in apples, pears, and quinces. This can easily be remedied by careful and systematic spraying with arsenate of lead. Although it may not appear so, codling-moth is one of the' easiest insect pests in the orchard to control, always provided that the main principles are adhered —namely, correct strength of arsenate of lead and thor-

oughness of applications at the. correct times. A knowledge of the habits of this insect at once indicates a method of intelligent control. We have learned that (1) it lives by eating the fruit, therefore we cover the latter with a weak poison, such as arsenate of lead, thereby destroying the grub; (2) the grubs hatch in late spring, and through summer from eggs laid by the female moth on the.' young forming fruit or leaves, consequently we commence spraying the young forming fruit early, and continue at frequent intervals throughout the summer; (3) as a large proportion of the grubs enter through the eye or calyx end, we endeavour to fill the calyx cavity with spray before it finally closes; (4) the grub changes into a moth, the female of which will lay eggs to hatch into more grubs, and we must therefore destroy all grubby fruit to reduce the numbers < for further ..infection. _

SPRAYING TREATMENT. From these considerations, therefore, the following spraying treatment is recommended: Proportions.—Arsenate of lead powder forth, loz. (if in paste form 20z.); water, 4 gallons. Preparation.—Weigh out loz. of arsenate of lead (powder) and place in a small-vessel; slowly add a very small quantity of water, mixing thoroughly all the time. When the whole is about the consistency of milk pour into a kerosene-tin or other vessel and make up to 4 gallons of water. This wash requires to be frequently stirred while being'used. Application. Spray when twothirds of the blossoms have fallen, with considerable pressure, and force the liquid into the “eyes” of the young fruit. Repeat every three weeks until February— Future applications will depend on district and

climatic conditions. Usually it is necessary to spray towards the middle of February, and in some of the northern districts again a month later. These late sprayings, in conjunction with the earlier ones, are also necessary for the control of leaf-roller caterpillar. In addition to . the spraying treatment advocated, it is absolutely necessary to gather all grubby fruit from the trees and ground as soon as they appear infested, so that it may be destroyed before the. grub leaves it. SCALE INSECTS. Scales, being sucking-insects, are found adhering to the bark of the tree or to the surface of the fruit and leaves, and are mostly armoured is, covered by a natural shell-like shield. Mussel — This is a scale which attacks the apple, pear, and plum, and where neglected treatment gives considerable trouble to orchardists through- x out the Dominion. If its presence is not detected and speedy and effective steps taken for its control, it spreads very rapidly, a large number of eggs being produced by the female insect during the season.

Maire Scale. native scale attacking deciduous and citrus fruit trees, ornamental trees, and shrubs generally. Infection from this pest spreads very rapidly. The scale is somewhat round, of a dirty-greyish colour, and usually about the size of a large pin-head. San Jose Scale. troublesome insect pest attacking both stone and pip fruits, and one which may be considered to cause considerable damage in the orchard if not detected and effectively controlled. This scale, as compared in size with those already mentioned, is miniature, is of a greyishwhite colour, and circular. Upon, close examination it may be found that the immediate centre is a yellowish colour, and in this respect it is easily distinguishable from the other scale insects mentioned herein. Treatment. The above-mentioned scales on deciduous fruit trees are easily controlled by spraying with win-ter-oil emulsion, 3 pints to 4 gallons of water, during the dormant season, preferably in July. However, if this spray has been omitted the young scales may be killed in the earlv summer, while they are on the move and before their shell forms and

hardens, with summer-oil j pint to 4 gallons of water, or nicotine sulphate (40 per cent, standard) -fifths of a fluid ounce (five teaspoonfuls to 4 gallons water), first dissolving 2oz, common soap in the water. WOOLLY APHIS. This is ah insect pest too well known to need much description. It attacks many varieties of apples, and is most destructive. Its appearance is easily noticeablea white woolly substance forming on the parts of the tree attacked. Infestation generally commences on the young wood or at the base of a leaf-stalk insect penetrating the wood tissues and sucking the plant-juices therefrom, causing the formation of warty growths on the parts affected. The insect increases rapidly, and, being protected naturally by the woolly substance and also by the growths and crevices caused bv its attack, it is very necessary in combating this pest by spraying that the compound used should be applied with considerable force in order that the insect may be well reached. Spraying is recommended as follows:During the dormant season, with winter-oil at a strength of 3 pints in 4 gallons of water; and during summer months, with summer-oil J pint to 4 gallons of water; or with nicotine sulphate (40 per cent, standard) fourfifths of a fluid ounce (five teaspoonfuls to 4 gallons of water) to which is added loz. of arsenate of lead (powdered form). Soap should not be used in this combination.

RED MITE. This pest, like the scales, is a suck-ing-insect living on the plant-juices of the leaves during the summer, and harbouring during the winter months in crevices in the bark or under forks of the branches, etc., on apple and stone-fruit trees. The insect itself is very small, brick-red in colour, and increases very rapidly, When neglected, the affected leaves are distinguishable at a considerable distance by their sickly appearance, and eventually drop off.' On apple trees the treatment during the winter is similar to that advocated for woolly aphisnamely, spraying with winter-oil emulsion at a strength of 3 pints in 4 gallons of water. For stone-fruits use 2 pints of oil in 4 gallons of water. For summer treatment spray with summer-oil J pint to 4 gallons of water, or with lime-sulphur 1-180 (equivalent to 4 fluid ounces to 4 gallons of water) several times at short intervals. It is advisable to allow an interval of at least _ three weeks to elapse between the applications of sulphurs and of summer-oil in order to avoid injury to the leaves. FUNGUS BLIGHTS. Fungus blights include black-spot on apples and pears, powdery mildew on apples, and leaf-curl on peaches and nectarines. Black-spot (Apples) This fungus winters on the fallen leaves, and when conditions are suitable in early spring spores develop. These latter settle on the leaflets at the base of the cluster of buds (known as blossom-buds) where the spores germinate and in due course attack the fruits. The spraying is directed to prevent their germination. APPLES. The following spray treatment for black-spot and powdery mildew control on apples is recommended:— (a) For Cox’s Orange Pippin, Sturmer Pippin, and other tender-skinned varieties—(l) Green-tip: Lime-sulphur, 1 pint to 4 gallons water. (2) Tight cluster of blossom buds (pre - pink stage) Lime - sulphur 8 fluid ounces to 4 gallons of water. (3) Pink: Lime-sulphur 4 fluid ounces plus colloidal sulphur loz. (weight) to 4 gallons water. (4) Petal-fall (when about 75 per cent, of petals have fallen): Limesulphur 4 fluid ounces plus colloidal sulphur loz. (weight) to 4 gallons water. (5) Remainder of summer: Repeat No. 4 application at about eighteenday intervals, according to weather conditions.

■ (b) For other varieties it is recommended that Bordeaux mixture (5-4-50) be applied at “green-tip” stage. To make this, use bluestone 6|oz., burnt lime, unslaked, s{-oz., and water 4 gallons. Subsequent treatment should be carried out during the season on the lines outlined above. Black-spot (Pears) The attack of this fungus is similar to that of blackspot on apples. PEARS. The following spray treatment is recommended for control of black-spot:-(a) For Winter Cole, Josephine, and other Tender Varieties of Pears, (1) Green-tip: Bordeaux mixture (5-4-50) lime. (2) Tight cluster of blossom buds: Lime-sulphur 8 fluid ounces to 4 gallons water. (3) Pink: Lime-sulphur 8 fluid ounces to 4 gallons water. (4) Petal-fall (when about 75 per cent, of petals have fallen): Limesulphur 4 fluid ounces to 4 gallons water. (5) Calyx (within ten to fourteen days petal-fall): Lime-sulphur 4 fluid ounces to 4 gallons water. (6) Remainder of summer: Repeat application No. 5 at about eighteen-day intervals according to weather conditions. (b) Other varieties of Pears—(l) Green-tip: Bordeaux mixture (5-4-50). To make, use bluestone 6Joz., burnt lime (unslaked) s|oz., and water 4 gallons. (2) Tight cluster of blossom buds (pre-pink stage): Bordeaux mixture (3-4-50). To make, use bluestone 40z., burnt lime (unslaked) 50z., and water 4 gallons. (3) Pink: Bordeaux mixture (3-4-50). (4) Petal-fall: Bordeaux mixture (2-3-50). To make, use bluestone 2Joz., burnt lime (unslaked) 40z,, and water 4 gallons. (5) Calyx (within ten to fourteen days petal-fall): Bordeaux mixture (2-3-50). (6) Remainder of summer: Bordeaux mixture lj-3-50. To make, use bluestone 20z., burnt lime (unslaked) 40z., and water' 4 gallons. Leaf-curl (Peaches and Nectarines). —The fungus causing this disease commences to become active at the “greentip” stage of -bud development in early spring, and is most troublesome during cold, wet seasons. It is readily held in check by spraying the trees in spring when the buds are swelling. Bordeaux at the following strength is advised:—Bluestone, 6|oz.; burnt lime. oz..; water, 4 gallons, mixed as directed. An alternative treatment for leaf.curl is as follows:Winter formula Lime-sulphur, 2 pints; water, 4 gallons.

PREPARATION OF BORDEAUX MIXTURE. The following directions apply to the quantities of bluestone and lime already given: — Dissolve the bluestone in 2 gallons of water; slake the lime slowly, in another vessel, and make up to 2 gallons; then pour both solutions . simultaneously into a third vesel. In using the mixture . during the dormant season' it should show a slight acid reactionthat is, when tested with litmus paper. Bluestone is readily soluble when placed in a piece of. sacking and al-

lowed to touch the surface of the water or suspended an inch or so below it, or by using hot water. The efficiency of Bordeaux mixture depends upon the intimate blending of the two solutions obtained by pouring both of them simultaneously into a third vessel. It is imperative that the chemicals used be pure and the lime fresh. The best results are obtained when the application is made as soon as possible after blending the two solutions. If allowed to stand for more than eight hours the fungicidal properties of the mixture largely depreciate. .

COMBINATION SPRAY. Lead arsenate -f- lime-sulphur: Addition of hydrated lime to avoid spray burn to the foliage. Dilute the required volume. of limesulphur in four . gallons of water; to the required quantity of lead arsenate add twice its weight of hydrated lime; mix with water to. form a thin paste, and pour it into the container holding the diluted lime-sulphur, stirring the spray while this is being done. Apply as rapidly as possible after mixing. Where to get local information on pest and disease control. further advice required may be obtained from the Department’s Orchard Instructor for the district. Remember, careful attention to simple instructions will enable the home gardener to ‘ avoid damage to his trees and obtain the satisfaction of gathering clean fruit.