A Plum Scale. 695 



HOW TO COMBAT THE SCALE. 



Whai to use.— This pest obtains its food from the inner tissues 

 of the tree by means of its sucking mouth-parts. Thus none of 

 the poisonous insecticides used to kill biting insects would have 

 any effect on this Plum Scale. It must be hit by some of the in- 

 secticides that kill by contact. The one that is the simplest to 

 make and which has been found the most eflfeclive here in the 

 east against scale insects is the Kerosene Emulsion.* If the di- 

 rections are carefully followed there is no trouble in getting a good 

 emulsion. This standard emulsion should always be diluted be- 

 fore it is applied to growing plants. But the number of times it 

 is to be diluted, will depend upon the insect to be killed. The 

 nymphs of the Pear Psylla, for instance, are readily killed by a 

 spray consisting of i part of the emulsion to 20 parts of water. 

 For most sucking insects it is diluted with 9 parts of water. But 

 our experiments indicate that this Plum Scale does not readily 

 succumb unless the emulsion as made by the formula is diluted 

 with only about 4 parts of water. That is, to one gallon of the 

 standard emulsion is to be added 4 gallons of water. A greater 

 dilution than this cannot be depended upon to do sure work. 

 There is not the slightest danger of this dilution of the emulsion 

 causing any injury to the tree, even when the leaves are opening 

 in the spring. Do not expect to kill a majority of the scales if 

 you dilute it with 7 or 8 or more parts of water. 



Wkeft to spray. — Between May and October, there is only 

 one period, of less than a week, in which the insect can be 

 combated effectively and practicably. Our experiments indicate 



* To make the emulsion, thoroughly dissolve one-half pound hard or soft 

 soap or whale oil soap in one gallon boiling water. While this solution is 

 still very hot add two gallons of kerosene and quickly begin to agitate the 

 whole mass through a syringe or force-pump, drawing the liquid into the 

 pump and forcing it back into the dish. Continue this for five minutes or 

 until the whole mass assumes a creamy color and consistency which will ad- 

 here to the sides of the vessel, and not glide off like oil. It may now be 

 readily diluted with cold rain water, or the whole mass may be allowed to 

 cool when it has a semi-solid form, not unlike loppered milk. This standard 

 emulsion if covered and placed in a cool dark place will keep for a long time. 

 In making a dilution from this cold emulsion, it is necessary to dissolve the 

 amount required in three or four parts of boiling water, after which cold rain 

 water may be added in the re(iuired quantities. 



