( Originally Published Early 1900's )
" Fruit growers, as a rule, understand that fungicides should be used as preventives, as when the spores have germinated and have penetrated the tissues the fungus has passed beyond the reach of a surface application. While some benefit may derive from spraying after the fungus is at work," writes Prof. L. R. Taft of the Michigan experiment station, " it is largely, if not entirely, in the way of preventing the spread of the disease to other parte of the plant or fruit.
" In a general way, then, it can be said that the only way to obtain perfect results from spraying is to make the first application before the attack, and renew it sufficiently often to keep all parts of the trees covered with the fungicide during the period of activity.
" So far as the insecticides are concerned, early sprayings are also necessary, as nearly all of the more troublesome insects injure plants by eating the foliage or other exposed parts. Although they can generally be held in check after the effect_ of their work has been noticed, it is better to apply the remedy just before the larva are likely to appear.
" As a rule, it is advisable to spray, not only apples, but all other fruits just before the blossoms open. This application will not only destroy many of the curculio, canker worms and other leaf-eating insects, but if done at just the right time the blossoms and blossom stalks can be coated with Bordeaux, and can thus be saved from the attack of fungi, to which they are subject if cold, wet weather prevails.
" A second application should always be made within a week after the petals have fallen. In cases where the first application was made at exactly the right time and it has not been washed off it will, perhaps, be fully as well to wait four or five days after the petals of a given variety have dropped, but it should by all means be completed within a week, and the sooner the better after the petals are off, unless one can be sure that. the young fruits are well coated with the fungicide. So far as the codling moth is-concerned, the best time for making this application will be after the stamens have had time to dry up and before the calyx lobes close.
" The third application should be made about two weeks after the second, or within three weeks from the time the petals have fallen, having in mind the importance of keeping the fruit and foliage covered with the spray mixture, and it may be desirable in some cases to shorten the period between the sprayings. This will be made at about the time that the first larvae of the codling moth hatch. Eggs will have been laid upon foliage and fruit over a period of perhaps three weeks, and will hatch in about ten days from time they are laid.
"This third spraying, then, should suffice to destroy practically all of the first brood, and, if the second spraying was properly done, the larva that are not destroyed while making their way to the calyx will be poisoned when they attempt to eat into the fruit at that point. One should have in mind the importance of keeping all parts of the trees coated with bordeaux and an arsenite at this time, as a protection against fungous diseases' and the codling moth, as well as other leaf-eating insects. If this third application is washed off before July 1 it should be repeated.
" At least one other application should be made to protect late varieties of apples from the second brood of the codling moth and from the attack f apple scab. The second brood of the codling moth does not, as a rule, hatch before the middle of August. The season may make a difference of ten days at any given point, hence no positive date can be fixed, especially as it is not uncommon to have the moths appear over a period of two to three weeks. They generally continue to deposit the eggs for a week or ten days.
"A fifth application is recommended for the codling moth to be given to winter varieties of apples from August 10 to 15. For this spraying it will generally suffice to use only an arsenite, except in cases where they are very subject to the attack of apple scab, and where the weather is favorable for its development, especially if the fruit and foliage do not seem to be well covered from the fourth spraying.
" For the spraying of grapes, pears, cherries, and European plums, exactly the same treatment is recommended so far as the first, second, and third applications are concerned. For Japanese plums the only change would be a slight reduction in the strength of the bordeaux, using only 2 pounds of copper sulphate, where 3, or perhaps 4, pounds might be used upon the other fruits.
SPRAYING STONE FRUITS
"For the spraying of peaches the substitution of 2 pounds of copper sulphate in 50 gallons of water is recommended in place of the first application of bordeaux. The spraying must be done during the latter half of March or the first half f April as preventive against the attack of the leaf curl. An application of weak bordeaux and an arsenite can also be made to advantage within a week after the fruit has set when the curculios are troublesome, or in the case of varieties whose fruit is subject to the attack of brown spot and other fungous diseases. Other sprayings are seldom desirable on account f the danger of injuring the foliage.
" The only exception would be in the case of the early varieties of peaches and plums and sweet cherries, which should be sprayed with either a self-cooked mixture of lime-sulphur or with a diluted solution when the fruits are about three-quarters grown, provided the conditions are favorable for the attack of brown rot.
"In the case of grapes that have been seriously injured by black rot, it is often a good plan to spray the vines while dormant with copper sulphate solution, 2 pounds in 50 gallons f water, or with bordeaux when the blossom buds first show, following it up with the first, second, and third applications mentioned above. As a rule, this will suffice. If there is much rot present the latter part of July upon unsprayed vineyards, and conditions are favorable for its spread, another application, which would be the fifth, if the above recommendations are followed, can be often made with profit. For this spraying it will be well to use no more lime than of copper sulphate, and a somewhat smaller quantity might be employed, thus lessening the danger of spotting the fruit. The same practice may also be followed when bordeaux is used upon winter varieties of apples and pears, or upon late varieties of plums after the first of August."
LATEST WORD ON SPRAYING
"Investigators of plant diseases have recently advanced important new ideas on spraying fruit trees," writes Prof. F. C. Stewart of the New York experiment station. " In circular No. 1, of the bureau of plant industry, W. M. Scott announces that he has devised a cheap and easily prepared lime-sulphur mixture which can be used on peaches and other fruit trees during the growing season without injury to foliage or fruit. He calls it the self-boiled lime-sulphur mixture. His experiments made in Missouri show it to be highly efficient in the control of peach rot and scab. The best proportions of lime and sulphur have not been determined definitely.
" The mixture that gave the most promising results was composed of 10 pounds of sulphur, 15 pounds of fresh stone lime, and 50 gallons of water. The lime is slaked with a few gallons of hot water. The sulphur is added immediately and thoroughly stirred into the boiling lime. The only heat used is that generated by the slaking of the lime. After boiling ceases, enough water is added to make 50 gallons. The mixture is then strained through a 20-mesh sieve and applied with a spray pump.
" If this new fungicide proves to have the qualities claimed for it, it will certainly be a great thing for peaches and may be useful for other fruits. However, we warn fruit growers against using it extensively until they have thoroughly tested it on a small scale. In the past, heavy losses have sometimes resulted from the use of new spray mixtures. It is best to go slowly with these new things. We understand that Mr. Scott made further experiments in 1908, but the results have not yet been published.
" Prof. A. B. Cordley of the Oregon station also has a lime-sulphur mixture, which he claims can be safely used on the foliage of fruit trees. He calls it the stock solution method of preparing lime sulphur mixture. He makes a stock solution of lime and sulphur, which gives a hydrometer test of 1.27. Each gallon contains 2.38 pounds of sulphur. Diluted with 15 parts of water this did not injure the foliage of apple, pear, plum, grape, potato, and celery, but did injure the peach. He states that apple trees sprayed three times with this mixture gave 79.3 per cent of scab-free fruit, while unsprayed trees gave only 19.9 per cent, and trees sprayed with bordeaux 49.1 per cent of scab-free fruit. Moreover, the fruit sprayed with lime sulphur was free from spray injury, while 39.1 per cent of the fruits receiving bordeaux showed spray injury.
" While we do not question the veracity of Professor Cordley, we cannot believe that the lime-sulphur mixture, in any form, is really more efficient than bordeaux fox the control of apple scab. A mistake has been made somehow. Our advice to apple growers is to continue to use 3-3-50 bordeaux as in the past.
"Probably many fruit growers have been alarmed by Colorado station bulletin No. 131, on arsenical poisoning of fruit trees. It is stated that in Colorado apple trees suffer from a disease in which the crown of the tree is girdled, the bark on portions of the trunk dead and sunken, and most of the roots dead. Dr. Headden, the station chemist, who made an investigation of this trouble, concludes that it is due to arsenic in the soil. When trees are sprayed with arsenate of lead or arsenite of lime, these substances eventually find their way into the soil and accumulate there.
According to Dr. Headden, the alkali in the Colorado soil renders the arsenic soluble, so that it may be absorbed by the apple roots. That arsenic in soluble form is extremely poisonous to plants is well known. Dr. Headden analyzed the soil under dying trees and found it to contain arsenic in dangerously large quantities. He also found arsenic in the wood of diseased trees. He holds that spraying with arsenical compounds is responsible for the death of the trees.
" In the minds of eastern orchardists who read this bulletin, the question will naturally arise, Does this apply to orchards in the east? In the past it has been assumed that, in our soils, the arsenical compounds used in spraying retain the insoluble form and so are not harmful to the trees."