17 



as much more for the labor. In other words, spraying with the 

 insecticides commonly emploj^ed, such as "distillate,'^ kerosene emul- 

 sion, and resin wash, may be safely estimated to cost about 2 cents a 

 gallon for the amount of liquid used, or not exceeding 2 cents per 

 individual tree under seven j^ears of age. On the other hand, gassing- 

 trees seven years old will cost from 12 to 15 cents per tree, or the 

 equivalent of from five to seven sprayings. The advantage, therefore, 

 of spraying, for the small owner, and for trees especially suited by 

 form of growth or pruning to such treatment, is evident. 



The oily washes are by far the best for use on citrus trees against 

 scale insects. The attempt has been made in various places to substi- 

 tute lye washes for the old standard kerosene washes, but the effect 

 has, as a rule, been disastrous. Lye strong enough to kill scale insects 

 applied to a tree, as demonstrated by Hubbard fifteen years ago, is 

 very destructive to the tender growth of the tree, and the damage from 

 the wash is often greater than that occasioned by the insects themselves. 

 In California, the kerosene and resin washes formerly used have now 

 given place, to a considerable extent, to a modification of kerosene 

 emulsion known as " distillate." As now employed, the washes in the 

 order of their popularity are; (1) Distillate; (2) resin wash; (3) kero- 

 sene emulsion. The probability is that distillate will ultimately sup- 

 plant the other two on account of its equal, if not greater, efficiency 

 and smaller cost. 



Distillate. — This wash was originated by Mr. F. Kahles, and has 

 found very general use in the Santa Barbara region, and also in the 

 lemon districts adjacent to San Diego, as well as in other citrus dis- 

 tricts in California. It is substantially an emulsion of crude kerosene, 

 made in the same way as kerosene emulsion, except that a greater 

 amount of soap and only half as much oil are used. Its cheapness 

 results from the latter fact. In spite of this lessening of oil it seems 

 to be, if an3^thing, stronger than kerosene emulsion. 



It is termed distillate spray, because the oil used is a crude distillate 

 of the heavy California petroleum, or the crude oil minus the lighter 

 oils. 



The emulsion or '"cream," as it is generally known, is prepared as 

 follows: Five gallons, "28"^ gravitj^," untreated distillate; 5 gallons 

 water, boiling; 1^ pounds whale-oil soap. The soap is dissolved in 

 the hot water, the distillate added, and the whole thoroughly emulsi- 

 fied by means of a power pump until a rather heavy, j^ellowish, creamy 

 emulsion is produced. For use on lemon trees it is diluted with 12 

 parts of water, and with 15 parts of water for the orange. The 

 "distillate cream" is prepared and sold by oil companies and private 

 individuals at from 10 to 12 cents a gallon, making the dilute mixture, 

 as applied to the trees, cost in the neighborhood of a cent a gallon. 



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