U. S. EXPERIMENT STATION BULLETINS. 409 



thing more with reference to the fertilizers: I did not mean to be under- 

 stood as condemning in the least the use of these substances for other 

 purposes. The effect on the fruit has been marked. It has been finer, 

 larger, and altogether better. I was talking about the prevention and cure 

 of yellows, and not of the use of these fertilizers for other purposes. 

 There has been more growth and better fruit on the treated blocks. I 

 ought to say a word more with reference to the plum. I think I mis- 

 understood Mr. Engle's question. 



Mr. Engle: My question was, whether it would prevent yellows by 

 budding on plums ? 



Dr. Smith: I understood the question to be whether yellows could be 

 induced in plums. Three years ago a thousand well-rooted Mariana plum 

 cuttings were picked out and peach buds worked upon them. These were 

 divided into three lots and set into three very badly diseased orchards 

 further up the Chesapeake and Delaware peninsula. It will be some years 

 before I can speak definitely as to results. 



SPRAYING FOR INSECT PESTS AND FUNGOUS DISEASES. 



SPRAYING FOR INSECT PESTS. 



The distribution of insecticide mixtures in the form of spray was first 

 begun in this country on a large scale during the early spread of the Col- 

 orado potato beetle in the western states. Paris green was first used in 

 1869 both as a dry mixture diluted with flour, ashes, plaster, or slaked 

 lime, and in liquid suspension in water. Spray machines soon came into 

 use, and this method of application of insect-destroying mixtures was 

 speedily extended to other insect pests. In 1878 poisoned spray was first 

 used against the codlin moth, and the entomologist of the department 

 had previously recommended this remedy for the cotton worm and several 

 other leaf-eating insects. During the progress of the investigation of the 

 cotton worm many spraying machines were developed, and from that time 

 to the present the development of methods and machinery has been rapid, 

 until at the present time the best remedies against perhaps the majority of 

 our principal insect pests comprehend the application of an insecticide 

 spray at one time or another. 



INSECTICIDES USED IN THE FORM OF A SPRAY. 



Kerosene emulsion. — This insecticide acts by contact and is applicable 

 to all non-masticating insects (sucking insects, such as the true bugs and 

 especially plant lice and scale insects) and also to many of the mandibulate 

 or masticating insects, such as the apple worm or plum curculio, when the 

 use of arsenites is not advisable. Kerosene emulsion may be made by 

 means of various emulsifying agents, but the most satisfactory substances, 

 and those most available to the average farmer and fruitgrower, are milk 

 and soapsuds. In each of these cases the amount of emulsifying agent 

 should be one half the quantity of kerosene. 



One of the most satisfactory formulas is as follows : 

 52 



