PREPARING MINERAL OIL FOR SPRAYING.

New Zealand Journal of Agriculture, Volume VII, Issue 1, 15 July 1913, Page 53

PREPARING MINERAL OIL FOR SPRAYING.

A MODIFICATION IN THE USE OF SOFT-SOAP.

A. H. Cockayne.

During the past few years winter spraying with mineral oils for the suppression of many sucking insects which appear to be controlled most easily during that season of the year has become very general in the orchard districts of New Zealand. This is especially true of all apple-growing sections of the Dominion where any of the scale insects or American blight are at all in evidence. The mineral oil that has secured fairly general adoption is one or other of the grades of the so-called red lubricating machinery-oils. These oils for spraying are generally procured in a condition denaturated with the admixture of a definite quantity 'of resin, thus avoiding the duty levied on similar oils that are not denatured. The oil requires to be emulsified by the grower before being applied. There are a number of proprietary compounds largely composed of mineral oils that are so prepared that they are immediately ready for applying so soon as the necessary amount of water has been added. For my part, I especially favour the use of these prepared oils, provided they mix easily and uniformly with water and do not develop any free oil on the surface. There appears -to be a prevalent idea that an oil is not effective if it does not thoroughly grease the tree and leave it in that condition for several weeks. As oils are supposed to kill insect life almost immediately, I cannot see the object of having the trees covered with a distinct oily coating for many weeks, and thus interfering with the normal functions of the bark. Again, trees that have been sprayed with an oil spray that leaves the trees oily for a considerable time are difficult to spray with Bordeaux, and this is a point worth consideration. A great many growers prefer to prepare the mineral oil for spraying themselves, and for this purpose soft-soap is nearly always used as the emulsifying agent. The following modification in the method of using soft-soap is suggested, having been found to be very satisfactory in a series of experiments that I have recently carried out: —■ Dissolve 4 lb. of soft-soap in 4 gallons of red oil by heating over a fire. The soft-soap dissolves in a very few minutesin a

much shorter time, indeed, than is necessary for the boiling of water. When the soft-soap is dissolved put both delivery and suction ends of the spray-pump hose into the oil and . work the pump steadily, at the same time pouring in slowly 2 gallons of cold water. Then dilute to the required strength. A very satisfactory emulsion is thus secured, far more rapidly than by the ordinary method. The great advantage of this modification is that a large quantity of oil can be dissolved with the soft-soap and can be put aside until such time as it is required. When spraying is to be done the prepared oil should be stirred well and the necessary amount. put into the spray-tank, when, with the aid of the hose and pump, an emulsion can be made rapidly. In general, half a ’ gallon of water will turn each gallon of oil into a satisfactorily thick emulsion. The - great advantage of this simple modification on the ordinary method is that no time is wasted at the time of application by having to heat water.