392 JOURNAL OF ECONO^nC ENTOMOLOGY [\o\. 9 



assimilated by the body. I feel sure that white gruljs will be shown to 

 have a positive food value, and am equally sure that the prejudice 

 against insects as food is perfectly unreasonable. 



Should any one following this experience be influenced to make any 

 personal experiments the probable necessity for thorough sterihzation 

 of the grubs before use should be pointed out on account of the effects 

 of possible pollution of the soil from which they came. 



REDUCING THE COST OF COMMERCIAL SPRAYING 

 By R. S. WoGLUM, U. S. Bureau of Entomology 



The question most frequently asked by the practical horticulturist 

 regarding a spray for the control of insect pests or plant diseases is the 

 cost of application. This cost is an important factor in balancing the 

 profit and loss account, namely the possible increased crop value less 

 •cost of treatment compared with the loss from the pest if no treatment 

 is given. The present article discusses briefly certain features of 

 •equipment which the writer has been using for more than a year with 

 marked reduction in the cost of certain sprays. 



One of the experimental plats used in an investigation of the control 

 of mealybugs of citrus trees in southern California consisted of ten 

 acres, and contained 1,125 trees. It was decided to use this plat in an 

 experiment to control the mealybug by a water spray, the object being 

 to wash the insects from the trees by water under high pressure. 

 Experience having demonstrated that upwards of 100 gallons of 

 water is frequently required for a single tree, it was apparent that 

 very few trees could be properly sprayed in a single day with a power 

 outfit, and, since three to five sprayings a year are necessary for 

 effective work, it was evident that such water control would be very 

 expensive. Furthermore, the contingency of one application closeFy 

 following another brought up the question of impracticability, if not 

 impossibility, of properly treating an orchard of this size with the one 

 outfit at our disposal. 



A very progressive grower near Pasadena had just installed a pipe 

 sj^stem in his orchard through which to force water in mealybug con- 

 trolj and this method of distribution appeared of such practical value 

 in treating large orchards that a pipe sj^stem was planned and im- 

 mediately installed in our experimental plat. A plan of this system is 

 shown in the accompanying figure. Some 2040 feet of f-inch pipe 

 were laid at a depth of about one foot, with uprights for attaching 

 faucets every fourth tree. A power sprayer having a 200-gallon tank 

 was stationed at one side of the orchard adjacent a water main from 



