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Testing Bordeaux Mixture.—In practice little attention is paid to the quantity of lime, except that sufficient is added to combine with all of the copper sulphate. To determine when this has taken place the potassium ferrocyanide test is made. Purchase ten cents' worth of potassium ferrocyanide, or yellow prussiate of potash, and dissolve it in water. Label it “ Poison.” Stir the Bordeaux mixture in the spraytank and take out a sample in a small vessel, to which add a drop of potassium ferrocyanide. If no change in color is noted where it dropped there is sufficient lime, but it is better to add lime solution equivalent to a pound of lime more. If the drop changed the color of the solution reddish brown it shows that there is not enoughi lime.

Strength of Solution. — For potatoes, 1 pound of copper sulphate to 7 or 8 gallons of water is commonly used; that is :

Copper sulphate (blue vitriol), 6 pounds.
Quicklime (not slaked), 4 to 6 pounds.

Water, 48 to 50 gallons. Bordeaux Dust,' or Dry Bordeaux Mixture, can be made in two ways :

1. Slaking the lime by pouring a strong solution of copper sulphate over it.

2. Mixing the strong copper sulphate solution with freshly slaked lime which has been made into a paste, then placing the mixture in a bag and drying and pulverizing it. The two ingredients must be well mixed and passed through a fine sieve. Dry Bordeaux is offered for sale under various names. Adler's Bordeaux is reported to be as efficient as newly mixed," but generally these preparations are much inferior to the newly prepared, and, when applied dry, are less effective than in the wet form.

1 For details, see Missouri Bul. 60. (N. Y.) Geneva Bul. 243, P. 325.

Washing Soda and Copper Sulphate Mixture. —This mixture is being used with success in parts of Europe. It does not clog nozzles, spreads evenly over the leaf, and is easily and cheaply prepared. The washing soda is dissolved in water, poured into the barrel of water and stirred, and the copper sulphate added and stirred. Various strengths are in use, but the most satisfactory one for American conditions has yet to be determined. We are trying 4 pounds of copper sulphate, 6 pounds of washing soda, and 50 gallons of water, adding 1 pound of lime if Paris green is used. A little over 1 pound of washing soda might be sufficient to neutralize the 4 pounds of copper sulphate, but it is safer to use more. In Ireland 5 pounds are used and for three successive years in extended trials this mixture has given better results than Bordeaux mixture.' At (N. Y.) Geneva Station, in 1904, it was not so good as ordinary Bordeaux mixture.

Spraying with Bordeaux Mixture.—Benefits.Spraying with Bordeaux mixture influences the potato crop in the following ways : ' 1. The structures of the leaf shows a slight increase

in thickness and in strength, and so offers more

resistance to the growth of disease spores. 2. The chlorophyll,' or green coloring matter of the

leaf and stem, is increased.

2 Me. Bul. 73, p. 55. 2 Department of Agric. for Ireland Leaflet, 14. : Frank & Krüger. E. S. R., VI., p. 306.

3. The transpiration of moisture is greater in

sprayed plants. Food is moved from the roots to the leaves in water, the food is worked over, and the water is given off. The more foodladen moisture passing through, the greater is

the growth. 4. The assimilation' or taking in of food from the

air by the leaves is much greater. 5. The duration of the leaves and vines’ is greater. 6. The growing period is extended (Fig. 41), insur

ing a heavier yield. In Vermont blight often appears in August, and from then on the potatoes have grown 50 bushels a week when the

foliage was preserved. 7. The tuber production is increased, due to increase

in the size of the tubers and the number of tubers per plant. Jones & Morse,' of Vermont, show that the average yield for thirteen years (1891 to 1904), without spraying, was 171 bushels per acre, while the sprayed plats yielded 286 bushels per acre, or an average annual gain

of 115 bushels per acre. 8. The dry matter is increased. 9. Starch formation in the tuber is considerably in

creased. At Geneva, (N. Y.) Experiment Sta

tionê an increase of 7 per cent. was obtained. 10. Where there is no disease’ the yield may be inCourtesy (N. Y.) Geneva Station

1 Frank & Krüger. E S. R., VI., p. 306 ? Vt. Report, 1899, p. 156. 3 Vt. Bul. 40, pp. 26, 27; Report, 1899, p. 272. Can. Exp. Farms Report,

1901, p. 120. 4 (N. Y.) Geneva Bul. 221. 5 Vt. Bul. 106, p. 231. ® (N. Y.) Geneva Bul. 221. " E. S. R., Vol. IX., p. 765. (N. Y.) Geneva Bul. 123, p. 234.


FIG. 41-SPRAYED AND UNSPRAYED PORTIONS OF A NEW YORK POTATO FIELD (Taken October 3, 1903.) Spraying extends the growing period, thus insuring a heavier yield.

creased by spraying, due to increased vigor of the plants. At the Vermont Experiment Station,' in 1900, the yield was increased 73 bushels per acre by spraying, although blight did not

appear that year. Time of Spraying.–Thoughtfulness, thoroughness, and timeliness are essential to success. A man must watch his crop, the season, and conditions; know for what he is spraying, and do it intelligently as well as thoroughly. In wet years spraying should begin earlier than in dry. The first spraying should be given early enough to ward off the first attack. At Vermont Experiment Station, in 1900," three applications were most economical, but the first one, that of July 26, was the most important, as half the entire gain was due to it; the sprayings on August 17 and September 8 were of about equal importance. At the same station,' in 1903, one timely spraying on August 1o insured a gain of 124 bushels per acre. Some growers who sprayed twice in July secured little benefit, because by the time the blight appeared, the latter half of August, their plants were unprotected. · No rule can be given; each man must watch for himself. In some districts it is profitable to give the first spraying when the plants are 6 inches tall, and repeat every ten to fourteen days, or as conditions demand.

Number of Sprayings.--At (N. Y.) Geneva Experiment Station,* in 1903, spraying potatoes five times gave an increase of 30 bushels per acre over three times, and three sprayings increased the yield 88 bushels per

1 Vt. Report, 1900, p. 272.
3 Vt. Bul. 106, p. 231.

? Vt. Report, 1900, p. 273.
- (N. Y.) Geneva Bul. 241, p. 262.

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