SPRAYING OF APPLE TREES,

Dominion, Volume 3, Issue 866, 12 July 1910, Page 8

SPRAYING OF APPLE TREES,

EXPERIMENTS ABROAD. At the big fruitgrowers' conference hold iii 'Wellington last November,, very great interest indeed was taken in tho subject of tho spraying of fruit trees. Tho exports of tho Department attended, and added to the value of the conference by tendering whatever advice they could, and no part of tho proceedings whs more interesting than tho demonstration, of the. emulsifying of oils given by Mr. A. H. Cockayne-, Government Biologist. The demonstration was in illustration of Sir. Cockayne's observations on spraying, which observations aroused more interest in that subject than had previously been awakened.

In tho last number of the "Journal of the Board of Agriculture" (London) there are two important papers relating to the spraying of apple trees, in one E. S. Salmon, F.L.S., deals with tho "Injury to Foliage by Bordeaux Mixture," and the oilier paper reviews the American experiments with lim<>sulphur wash.

"Bordeaux injury." From time to time, according to ttio writer of the former paper, injury resulting from spraying in certain seasoils has been reported. Such injury has been variously termed "Bordeaux injury," "spray injury," "scald," "burning," "spray russeting," "cork russeting," and "yellow leaf," and has been reported from most of tho applegrowing districts of New Zealand, Tasmania, Australia, North America, and Kuropu. "The injury which I have noted," ho continues, "as sometimes following , the application of Bordeaux mixture on apple trees becomes evident sometimes on the leaves and sometimes on the fruit. With regard to the leaves, these may show (1) local injuries in the form of brown spots which soon drop out. and, when tho purtions afleoU-ri fall'froin the central part, give it "sbov holo" appearance to the leaf, while if the portions affected fall from the edges of the leaf, a jagged or notched appearance is. given Mi thu taaf, at first suggestive of the action- of caterpillars; (2) a "scorching" of tho edges or tip of the leaf, or the formation of brown patches which do not fall out; (3) a yellowing or browning of the wholo leaf, which subsequently falls. In my experience tho "shot-hole" effect on tho leaves is the form of injury which results when 'a too heavy spraying is Ijiven As regards the fruit,

this may sometimes show injury in that the apple become? rough and "russotcd," due. to the formation of dead corky cells at tho places where tho action of the spray has caused a rupturing of the skin; in cases of severe injury the apple cracks.' . . . The actual causes of Bordeaux injury are still very obscure; it seems clear, howbvor, that subsequent chemical changes m' the Bordeaux mixture after it lias been sprayed on the plant and thero imposed to various weather conditions (especially wet weather) arc largely uonconieu in causing the injury." How to Avoid injury. "The practical suggestions given in this bulletin to fruit-growers how to avoid the injury are as follow:—(1) In spraying use less copper sulphate, give the 3-3-i>o formula (equivalent to 3 3-51b. copper sulphate, 3 3-51b. quicklime, to 50 imperial gallons) for Bordeaux mixture a thorough trial. Spray in moderation ; spray to cover the i'oliagf; and fruit with a thin film and yet not have the trees drip heavily. So far as possible the Bordeaux mixture should 'bo used only in dry weather. Use equal, amounts of lime and copper sulphate.(y) Some varieties of apples may be sprayed without much fear of injury. Others must be sprayed witli great care. Distinguish between tho varieties in spraying oiit'Pstian.s, (3) Many varieties of apples are nearly immune to attacks of the 'scab' fungus. Those need comparatively light applications of Bordeaux mixture in the ayerago season. (4) Bordeaux mixture is tho best fungicide known to the applngrower. Its use cannot be given up in fighting tho apple 'scab,' even though it cause some injury; apple 'scab' causes a. far greater loss than 'Bordeaux injury. , ... In view of tho fact that it is practically impossible to keep any considerable acioagn of apples free from 'scab' or 'black spot' without spraying with Bordeaux mixture, tho fruit-grower should pay attention to the-following:—(1.) Uso a nozzle which throws a fine' 'misty' spray; spray tho trees lightly, and leave oft' before the trees begin to drip. (2) Distinguish between tho different varieties of apples, giving those which aro liable to show 'Bordeaux injury , a vWy light spraying with Bordeaux mixture made of 3lb. copper sulphate, 31b. i|uicklimo (in lumps), 50 gallons of water (mixed as described above); or apray such varieties experimentally with tho lime-sulphur wash, described ai; p. 022 of Vol. XV of this Journal. (Fruit-growers must remember,' howovor, that although some success has lately been obtained in tho United States with the lime-sulphur wash as a fungicide for use on tender-leaved fruit trees, it in unquestionably inferior to Bordeaux mixture as a general fungicide.) (3) Concentrate attention in spraying on those varieties whoso leaves get 'sooty' with tho 'scab' fungus and whose young wood gets 'scab'infested; varieties 'resistant , ' to 'scab' do not, as a rule, require to be sprayed. (4) Spray directly tho blossom has fallen, and, where necessary, again whon the apples arc about three-quar-ters grown. 03) Use freshly-mixed home-made Bordeaux mixturo prepared from tho best freshly-burnt quicklime I (in lumps)."

Lime-Sulphur Mixture. Regarding the- lime-sulphur mixture Lhe following extracts, aro of interest: "A lime-sulphur solution containing, when diluted, about 41b. of sulphur to 50 gallons of water, appears at present to bo th(> most promising preparation. This may bo obtained by using tljo commercial solution at the rate of gallons to 50 gallons of water, or by preparing the lime-sulphur 'solution at home and. diluting it so .that each ol) gallons will contain 41b. of Kulphnr. Tho mixture at this strength injured Applo foliage in Virginia very little, and if these results could bo taken ns a reliable guide, there need bo no hesitancy in using it; but, under different conditions the results might bo different, and the matter must still be considered as moro or less experimental. A strength of 1$ gallons of the commercial solution may prove to be sufficient in most cases, and the danger of injury would then, perhaps, bo entirely eliminated.

Tho experiments made by the Department of Agriculture, in 1908 and 1909, as well as the published records of other investigators, show that the limosulphur ■solution <n apparently as effective as Dordcaus mixture in the control of apple scab. Limc-suiplnir will control leaf-spot and other minor troubles, as well as applo scab, but so fa.r it has not proved to bo a satisfactory remedy for applo blotch (Pliyllosticta.) or bitter-rot. However, tho experiments on those two diseases liavo not been carried far enough to determine what may bo expected of it in this connection. . . . According to

- v "VA-'jjuiiif; „ ,)io information at hand, arsenate 01 Jcad is uno,uestionub)y tie poison to

use iviih tlio lime-sulphur mixture. . . . According to tho results obtained in tlu» Arkansas osppriiKtni, three applications of the commercial solution at a strength of 1 gallon to 30 ;;:illoiis may bo made without material injury to apple foliage, hut after the fourth application tho injurious effect becomes serious, and after tho fifth the injury is almost disastrous to both fruit :iini foliage. It appears, therefore, that tho injury is cumulative, and that it is unsafe, to make more than three applications, or four if one is made beforo the trees bloom."