Strong lime-sulphur to be used on dormant trees or bushes for scale insects, can be prepared in three ways :
By the old formula,
By reducing with water “the home-made” concentrated wash. By reducing with water the “commercial” concentrated wash.
The “Old formula” has been used for many years with good results and is very satisfactory. The formula is as follows :
Lump lime 20 pounds
Sulphur (flour) 15 pounds
Water (hot) to make 50 gallons
The lime is slaked with a small amount of water (hot if lime is sluggish) and the sulphur is added, fifteen or twenty gallons of water are then added, and the mixture boiled. (It should take three-quarters of an hour, or an hour of good boiling with frequent stirring.) When done the liquid should be amber colored and fairly clear. Strain, dilute with water (hot is preferable) to make (up to) 50 gallons, and apply warm, through a coarse nozzle.
If small quantities are required, use an iron kettle to boil it in. If larger quantities are to be used, live steam is preferable for boiling purposes, either in a tank or in barrels.
Applied just before the buds swell, it coats the branches in such a way as partially to hinder from settling down, such pests as the oyster-shell, scurfy scale, some aphids and other insects.
HOME-MADE CONCENTRATED LIME-SULPHUR WASH.
Growers, having cooking plants, can make the lime-sulphur wash in a “concentrated” solution. This may be an economy of time, as large quantities can be made early in the season and stored until needed.
It is difficult to make this wash of uniform strength. For this reason, every batch that is made must be tested with a hydrometer and diluted accordingly.
The difficulty of getting a solution of uniform strength, apparently depends on the lime, which varies in composition and strength. Lime that contains more than five per cent of magnesium oxide and less than 90 per cent of calcium oxide does not combine in the cooking with the sulphur in a way to make a good mixture. Special “spraying lime” is now on the market.
The lime is slaked to a thin paste and the sulphur is added. Boil for one hour and stir frequently. Water enough should be added so that there will be fifty gallons at the end of boiling.
After it is cooked, if not to be used at once, it should he strained into a barrel which should be air tight, as exposure to the air causes the sulphur compounds to lose their value for spraying purposes. Each lot that is cooked should be tested with a hydrometer when cooled and di luted, according to the dilution table on page 365, when applied :
COMMERCIAL CONCENTRATED LIME-SULPHUR WASH.
There are several brands of the “commercial” concentrated lime-sulphur solution now upon the market. The use of these instead of the home cooked kinds is becoming more and more common every year, especially by fruit growers who do not care to take the time or trouble to cook the material for themselves or if they do not have good facilities for doing so. They are now reasonable in price,of fairly uniform strength, and do add to the ease of getting ready to spray as all that is necessary is to dilute with the required quantity of water.
FORTY-SECOND ANNUAL REPORT. 161 TESTING AND DILUTING CONCENTRATED LIME-SULPHUR.
Every “batch” of the home made concentrated lime-sulphur wash will have to be tested when cooled to determine its strength and it will be well to test the “commercial” brands. This testing is done with a Baume hydrometer. It is a simple instrument used to determine the weight and density of liquids. It is made of glass, is about a foot long, and has a graduated scale on the side.
It is absolutely necessary that the hydrometer be kept perfectly clean. If the solution is allowed to dry on it an accurate test cannot be made.
It can be purchased from dealers in druggists supplies or from Bausch and Lomb Optical Company, Rochester, N. Y., Whitall Tatum Company, Philadelphia, Pa., or Taylor Instrument Companies, Rochester, N. Y. (See page 169 for the rates of dilutions.)
SELF-BOILED LIME SULPHUR MIXTURE.
This is a mixture of lime, sulphur and water and not like any of the other lime-sulphur sprays. It does not (when properly made) injure tender foliage and is very valuable for spraying peaches and Japanese plums.
The formula is :
Lump lime 8 pounds.
Sulphur 8 pounds.
Water 50 gallons.
The mixture can be prepared better by using thirty-two pounds of lime, thirty-two pounds of sulphur, and eight or ten gallons of water, and then diluting to 200 gallons.
Place the lime in a barrel and add enough water to almost cover it, as soon as the slaking begins, add the sulphur, which should be run through a sieve to break up the lumps.
Stir constantly and add enough water to make a thick paste and then, gradually, a thin paste. As soon as the lime is well slaked, cold water should be added to cool the mixture and prevent further cooking. It is then ready to be strained into the spray tank, diluted up to the full formula, and used.
Care must be taken not to allow the boiling to proceed too far, if the mixture remains hot for fifteen or twenty minutes after the slaking is completed, some sulphur will go into solution and injury to the foliage may result.
The time of adding the cold water to stop the boiling depends upon the lime. With a sluggish lime all the heat in it may be needed, while with limes that become intensely hot, care must be taken not to allow the boiling to proceed too far.
SOLUBLE SULPHUR POWDER.
There has appeared on the market a form of sulphur compound that can be dissolved in water, and is recommended as a substitute for lime-sulphur. It has been tested in a limited way by this Experiment Station ; one apple tree; badly infested with the San Jose scale was sprayed in March 1912. Frequent examinations indicated that the scale was destroyed. More extensive experiments are in progress.
Bordeaux mixture is made of copper sulphate, lime and water.
These three substances are combined in various proportions, depending upon the kind of plant to be treated. For apples, pears, cherries and plums (except Japanese varieties) the preparation is usually four pounds of copper sulphate, with about the same amount of lime, to fifty gallons of water. Poison is added as needed. The copper sulphate will readily dissolve in two gallons of hot water, to which should be added enough water to make twenty-five gallons or one-half barrel. Do not use an iron or tin vessel to dissolve this in, as the copper sulphate will destroy it, and besides the iron will spoil the Bordeaux. A wooden pail is good. Slake the lime into a thin paste and add water to make twenty-five gallons. Pour, or let these run together into a third barrel, and the Bordeaux is made. When it is emptied into the spray barrel or tank, it should be strained through a brass wire strainer to catch any of the coarse particles.
Whenever it is necessary to use a quantity of the mixture, it is desirable to have the lime and the copper sulphate in “stock solutions.” A quantity of lime is slaked to a paste and held so by being covered with water. The copper sulphate, say fifty pounds, is placed in a clean gunny sack and suspended in a barrel (one with wood hoops is much to be preferred) containing twenty-five gallons of water. This will dissolve in about a day. One gallon of this “stock solution”* is equal to two pounds of copper sulphate.
A good quick way to combine these three substances is as follows : Put the amount of the “stock solution” of copper sulphate required in a barrel, and add enough water to make 25 gallons, or one-half barrel. Put about 7 pounds of the lime paste in a barrel and add 25 gallons of water, making a thin whitewash. Pour, or let these two run together into a third barrel, or directly into the spray barrel or tank, being sure to strain. When partly run in, test with ferro-cyanide of potash to make sure enough lime has been used. If Paris green, arsenate of lead, or any other poison is to be used, make it into a thin paste with a little water and add it to the Bordeaux mixture, which is now ready to be used.
COPPER SULPHATE SOLUTION
Is copper-sulphate dissolved in water. It is used by some growers to spray peach trees to prevent the leaf curl where a spraying for scale insects is not required. Two pounds of copper sulphate to 50 gallons of water is strong enough for this purpose.