Lime-Sulphur.—The more important fungicides, the commercial lime sulphur and the self-boiled lime-sulphur, are practically superseding Bordeaux as a fungicide, not because they are necessarily better, but because there is frequently much burning of the foliage and russeting of the fruit from the use of the Bordeaux. This is unfortunate as the latter is a rather more effective fungicide as well as more convenient and pleasant to use. The self-boiled lime sulphur is a combination of lime and sulphur which is boiled by the heat of the slaking lime alone, and makes a pretty good substitute for the Bordeaux when it injures foliage or fruit. This preparation of lime and sulphur differs from the commercial form used as a winter wash in that it is wholly a mechanical mixture and not partly chemical like the latter. It may therefore be used on the foliage in summer at a greater strength, there being only a very small percentage of sulphur in solution when the mixture is properly made.
Equal amounts of lime and sulphur are used, these being from eight to ten pounds each to fifty gallons of water. The mixture is best prepared in larger quantities so as to get heat enough from the slaking lime to produce a violent boiling for a few minutes. First, place say forty pounds of lime in a barrel and pour on just water enough to start it slaking nicely—about a gallon to each three or four pounds of lime is usually sufficient. Then add the sulphur and enough more water to slake the paste, keeping it well stirred meanwhile. The violent boiling of the lime in slaking will cook the mixture in from five to fifteen minutes, depending on the quality of the lime and how fast it is slaked. Just as soon as the violent boiling is over add enough cold water to stop all action. If this is not done, some sulphur will unite with the lime and burning may be the result.
This self-boiled mixture is entirely harmless to apple foliage and even appears to have a stimulating effect upon it. Against the apple scab, however, it is not as effective as the boiled wash, or the commercial preparations. For this disease a strength of from one to thirty to one to forty (that is about one and one-half gallons of the prepared mixture testing 31 to 33 Beaumé to fifty gallons of water) of the commercial lime-sulphur is most effective.
Spray Pumps.—The application of the foregoing spray mixtures is fully as important as the sprays themselves, for on the right application at the right time depends the efficacy of the spray. For this purpose a considerable amount of special machinery has been devised. Lack of space prevents us from going into much detail on this question, so we must be content with merely outlining the different types of machines and mentioning their accessories. Sprays are forced through single, double or triple acting pumps, either by hand or power. The three types of power available are traction, compressed air, and gasoline, the last being the most used. Steam power is practically obsolete.
The knapsack is the simplest type of hand pump, but it is of no practical use in the mature apple orchard. For small orchards and small trees several types of hand pumps are quite effective. The lever type of pump, where the handle is pushed from and pulled toward the operator, probably gives the most power with the least tiring effect, because it enables one to use the weight of the body to some extent. It is best not to have the pump attached to the spray barrel or tank, but set on a movable base of its own, as then it can be used for any one of a number of barrels. Such an outfit may be obtained for from twenty-five to forty dollars.
It is well to buy a standard make of pump, preferably from a nearby dealer, so that repairs may be readily secured. For all orchards up to three or four acres in size, and for larger orchards where the trees are not over twelve or fifteen feet in height, this kind of spray rig is the most practicable and advisable, when the expense is taken into consideration. This applies especially to the general farm.
The power of a traction sprayer is developed from the wheels. There is much discussion as to whether sufficient power to throw an effective spray can be supplied by this method. By accumulating considerable pressure by extra driving at the ends of the rows and then skipping every other tree in order to keep up the pressure, going over the rows twice, a very satisfactory pressure can be obtained for trees which are not too large. The argument for this type of machine, and it is especially applicable on the general farm, is that it can be used for other spraying on the farm as well as for the apple orchard, especially for potatoes and small fruits. It is a comparatively cheap type of power, particularly when it can be used for several purposes.
The compressed air gas sprayer comes next in point of simplicity and cost for a power sprayer. Its most economic use is found where orcharding is carried on extensively enough to pay to compress the air or gas right in the orchard. This is of course impracticable on the general farm. Therefore the air or gas must be purchased and shipped to the farm in steel tubes. This often causes delay at critical times and is rather expensive. Moreover, the gas is open to the objection of interfering with the lime-sulphur compound by precipitating some of the sulphur.
The gasoline engine is the most useful and popular type of power for the orchard sprayer, as well as for general use on the farm. Many makes are now so perfected that they give little or no trouble. One and a half or two horsepower are fully sufficient for spraying, but most farmers prefer from three to five horsepower in order to be able to use the engine more for other purposes. The latter power is open to objection for spraying purposes on account of its weight, as especially in early spring it is very difficult to haul so heavy a rig over the soft ground. Such an outfit is also rather expensive. Standard makes of gasoline engines of sufficient power for spraying cost from $75.00 to $150.00 according to horsepower and efficiency. For very large trees, for mature orchards, and for all orchards larger than four or five acres, the gasoline engine is the best source of power for spraying, particularly where it can be used for other purposes on the farm.
A double acting or two cylinder pump is most desirable. If there is plenty of power a triplex or three cylinder pump is still better. The requirements of a good pump are: sufficient power for the work desired of it; strong but not too heavy; fewest possible number of parts consistent with efficiency; brass parts and valves; and a good sized air chamber. A number of standard makes of pumps answer these conditions very well. Pumps should always be washed out with clean water when the operator is through with them and the metal parts coated with vaseline. Never leave water in a pump chamber or in the engine jacket in cold weather.