THE MONTHLY BULLETIN. 139 



4. Spraying is nsually more economical than sprinkling, and the 

 effect on the soil is apt to be less injurious, as much less poison is 

 required. 



5. Morning-glory and many other plants can be killed to the ground 

 without apparent injury to the soil by spraying with a solution of one 

 gallon of the stock solution given in Formula 3 diluted to one hundred 

 gallons. In some of the experiments the roots also of the morning- 

 glory have been killed to a depth of over four feet by this treatment, 

 but the roots are not always affected. The conditions necessary to kill 

 the root system of morning-glory by the spray method are still unknown, 

 but ail attempt is being made to determine them. 



6. It seems evident that the maturing of seeds on noxious weeds can 

 be economically prevented by the spray method, provided the condi- 

 tions are such that the spray can be applied without injury to culti- 

 vated crops. Weeds growing along canals, roadways, and fences, or 

 other places where cultivation is difficult or impossible, would not be 

 such a menace to the fields if the tops were killed to the ground 

 at sufficiently frequent intervals to prevent their maturing and scat- 

 tering seeds. 



For this purpose a spray of sodium arsenite is recommended, equiva- 

 lent to 4 pounds of arsenic trioxide per 100 gallons of water, to be 

 applied to the foliage as a fine mist by means of an efficient hand or 

 power sprayer. 



A spray of practically the above concentration may be made as 

 follows : 



Formula 1, diluted to 1^ gallons. 



Formula 2, diluted to 25 gallons. 



Two fluid ounces of Formula 3 diluted to 1^ gallons. 



One quart of Formula 3 diluted to 25 gallons. 



One gallon of Formula 3 diluted to 100 gallons. 

 The writer wishes to acknowledge the assistance of ]\Ir. William 

 Wood, Horticultural Commissioner of Los Angeles County; Mr. Fred 

 Seulberger, Horticultural Commissioner of Alameda County; his chief 

 deputy, Mr. D. P. T. McDonald; Horticultural Inspector Mr. W. H. 

 Tyson; Mr. A. A. Brock, Horticultural Commissioner of Ventura 

 County; ]\Ir. C. W. Beers, Horticultural Commissioner of Santa Bar- 

 bara County ; Mr. F. W. Waite, Horticultural Commissioner of Imperial 

 County; Mr. Fred Lowrie and Mr. George Lowrie of Centerville. who 

 have facilitated the experimental work in various ways through encour- 

 agement, offering transportation when needed, furnishing land for the 

 experiments, and conducting independent experiments; and of their 

 assistant, Mr. C. C. Barnum, who has been of invaluable aid in the 

 planning and execution of the experiments. 



