REPORT OF L. R. TAFT ON EXPERIMENTS WITH REMEDIES FOR THE APPLE SCAB.

SIR: I have the honor to submit herewith my report on the experiments made the present season in the treatment of apple scab.

Respectfully,

L. R. TAFT,

Agricultural College, Michigan.

B. T. GALLOWAY,

Chief of the Section of Vegetable Pathology.

Early in May arrangements were made for the purpose of testing the effect of various fungicides upon the apple scab.

Five formulæ were received from the Department with instructions to test each of them on two trees, and to have two other trees unsprayed for comparison.

When the trees were in blossom twelve were selected that appeared of equal vigor and that promised fair crops of fruit. The college orchard in which the trees are growing is now thirty-two years old, and has been cultivated without crops for the last four years. In 1887 it produced a full crop; last year the crop was a small one, but the trees will average about 5 barrels of marketable fruit this year.

The Northern Spy was chosen as the variety to be experimented upon on account of its liability to injury from scab.

The trees were on the north end of the orchard near the public road, and were all within the space of a half acre. They were treated as shown below, the numbers indicating the solutions.

On the 22d of May the trees were sprayed with London purple at the rate of 1 pound to 200 gallons of water.

First application.-The first application of the fungicides was made during the forenoon of May 24, when the apples were the size of large peas and before any trace of scab was apparent. Care was taken to cover every leaf and fruit, requiring about 3 gallons for each tree. The following were the solutions employed:

No. 1. Potassium sulphide dissolved in water at the rate of 5 ounces to 10 gallons of water.

No. 2. Sodium hyposulphite dissolved in water at the rate of 1 pound to 10 gallons of water.

No. 3. Sulphur solution, from E. Bean, Jacksonville, Fla., used at the rate of 1 pound to 10 gallons of water.

No. 4. Copper carbonate and ammonia. Prepared by mixing 3 ounces of copper carbonate with 1 quart of ammonia, and as soon as all action had ceased diluting to 22 gallons.

No. 5. Modified eau celeste. Dissolved 2 pounds of copper sulphate in hot water and in another vessel dissolved 24 pounds of sodium carbonate. Mixed, and before using added 14 pints of ammonia, then diluted to 22 gallons.

All these were applied except No. 3, which was not received until the 1st of June.

A Little Climax pump, manufactured by the Nixon Nozzle and Machine Company, Dayton, Ohio, was used for applying the solutions. With a long hose, fastened to a pole 10 or 12 feet in length, we were able to reach the highest branches with a fine mist-like spray. The pump seems adapted to this kind of work, and gave good satisfaction except that the valve in the piston troubled us by sticking whenever air was allowed to enter.

The time required for applying the fungicides was about ten minutes per tree, but this would be greatly lessened were large orchards to be treated, when, with a large Nixon or field pump, not over three minutes would be needed for spraying a tree.

The weather at the time of the first application was pleasant but slightly cloudy. The four following days were warm and sultry. Rain fell on the 29th and continued at intervals until June 4.

Second application.-On the 6th of June the second application was made, between 1 and 3 p. m.; at that time no appearance of scab could be detected and no injury from any of the solutions was observable. The afternoon was warm and pleasant, the mercury standing at 800 Fahr. Rain fell during the night, however, and continued slightly for the next two days.

Third application.-The treatment was repeated on the afternoon of the 12th, the weather at the time being similar to that of the 6th. The scab had not yet manifested itself on any of the fruits, and none of the solutions showed any injurious effect.

Fourth application.-The afternoon of June 25, was taken for making the fourth application. The weather was warm and the sun hidden by thin clouds. For the last twelve days the temperature had been low, with cold nights and frequent showers.

The scab had now made its appearance on all of the trees, affecting both leaves and fruit. The amount of scab on the trees sprayed with the copper solutions was quite small, and was found on the remaining trees in amounts increasing in about the following order: Potassium sulphide (No. 1), sodium hyposulphite (No. 2), sulphur (No. 3), and unsprayed (No. 6). In all cases it appeared to be about the same on the duplicate trees.

A slightly injurious effect was now observable from the use of the hyposulphite, as the edges of the leaves appeared to be turning brown. The trees sprayed with the copper solutions had their fruits somewhat discolored in streaks, where the epidermal cells were destroyed. This gave them a russet appearance.

Fifth application.-All the trees were sprayed on the 6th of July,

between 8 and 10 a. m. The morning was clear, with a temperature of 78° Fahr. At this time, and for all future sprayings, the sodium hyposulphite was reduced to 1 pound to 12 gallons of water and no further injury was noticed. There was no change in the appearance of thescab. From June 25 to July 14, there were no showers, but on the 14th and 15th a steady rain fell.

Sixth application.-On the 24th of July the sixth application was made between 1 and 3 p. m. The sky was clear at the time and the mercury stood at 77° Fahr. Only one tree of each lot was sprayed, those marked (a) not receiving any of the solutions.

There was a very slight increase in the size of the spots, but very few new ones were apparent.

Seventh application.-The seventh and last regular application was made on the 1st of August between 1 and 3 in the afternoon. The sun was obscured and the mercury at 77° Fahr. For the past three weeks the weather had been moderately warm, with several heavy showers. During one of them large branches were broken off from one tree, treated with the carbonate (No. 4), and from the check tree (No. 6a.)

During the early part of the summer the weather was favorable to the development of scab, and the numerous showers made frequent application of the fungicides necessary, as all except the copper solutions are easily washed off. The mixtures, Nos. 5 and 6, however, were retained on the trees for several weeks, as when the leaves dropped in October they still showed traces of the application made the first of August.

After the middle of July but little rain fell and but little change was noticeable in the size or number of the scab-spots. These varied in size from one-sixteenth to three sixteenths of an inch with an average diameter of less than one-eighth. On very few fruits was the injury sufficient to render them unmarketable.

During the season the fruit was examined by a hundred or more persons, and at my request many of them made an estimate of the amount of scab on the different trees, and although they did not agree as to the per cent. of injury on the different trees, there was no difference of opinion as to the relative benefit derived from the various fungicides. Throughout the season this appeared the same.

On the 1st of October the fruit and leaves were examined to see what difference could be detected in their appearance.

No. 1 and No. 1a. Trees sprayed with potassium sulphide. The foliage shows no effect of the fungicide. The fruits appear to be at least two-thirds affected but the spots are all small. Both trees are noticeably more highly colored than any of the others. No cause cau be assigned for this except that in some way it was owing to the potash. The total amount used was only a half pound for a tree, in the form of the sulphide. At the time of application very little of it reached the ground, and although it was washed off by the showers it hardly seems possible that it could reach the feeding roots in a season as dry as last summer. No. 2 and No. 2a. Trees sprayed with sodium hyposulphite. The edges of the leaves are quite brown from the spraying early in the season. The fruit shows more scab than the last.

No. 3 and No. 3a. Sprayed with Bean's sulphur solution. The fruits seem slightly less injured by the scab than do the unsprayed trees.

No. 4 and No. 4a. Sprayed with copper carbonate and ammonia. Traces of the copper can still be seen on the leaves. The fruits are not highly colored and are slightly marked with russet from the injury to the epidermis in June. Less than half the fruits seem affected by the scab.

No. 5 and No. 5a. Sprayed with modified eau celeste. Similar in appearance to No. 4, except that the russet streaks are more noticeable and that the scab is much less injurious. No. 5a, which is on higher ground than No. 5 and received two more applications, is not apparently affected by the scab. The few fruits on which it is present show only one or two very small spots. The fruit is of a large size and very regular on both trees.

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No. 6 and No. 6a. Unsprayed. The fruit on these trees does not differ from that of the other unsprayed trees in the orchard. Ninetenths of the fruits have one or more spots, and the scab spots are much larger and more numerous on the fruits than on No. 4 or No. 5.

The picking was commenced on the 5th of October. The fruit was assorted into three grades: (1) those entirely free from scab; (2) slightly injured; (3) badly affected. Each lot was then counted and weighed, with the results found in the following table:

The tree No. 5, sprayed with modified eau celeste, showed only 11.8 per cent. of scabby fruit, while the unsprayed trees had 87.5 per cent. No. 5a, which was on lower ground, received two applications less than No. 5, and bore nearly twice as much fruit, had 40 per cent. that showed traces of scab. We have no means of determining to which of these causes the difference should be attributed, but from the effect in other cases it is quite likely that the large crop of fruit borne by the tree had more effect than either of the others.

The effect of the scab, so far as the value of the crop is concerned, is two-fold: (1) the size of the fruit is reduced, and (2) the presence of scab to any extent renders the apples unsalable as first-class fruit, and they can only be disposed of as "seconds," or, if badly affected, for cider.

The average of the results obtained this year show that the apples