Plant-Diseases and Insects. 



107 



trees imported from the eastern States ; and while they may 

 not have the disease in the localities where they get this stock, 

 but we, having no guarantee that the eastern growers may not 

 get trees grown in infested sections to supply the California 

 demand ; therefore be it Yellows 



" Resolved, That we warn intending purchasers of the dan- agitation, 

 ger of getting trees infected with the yellows and other tree 

 diseases and pests not now in this State ; and be it further 



" Resolved, That we call the attention of all the boards of 

 county horticultural commissioners and quarantine guardians 

 throughout the State to this danger, and urge the rigid en- 

 forcement of the law in all such cases." 



This experiment of endeavoring to exclude a contagious 

 plant-disease from a given territory will be watched with keen 

 interest by the scientific world. There is a strong feeling 

 against this movement among eastern nurserymen, who con- 

 tend that the California nurserymen are using the law to pre- 

 vent competition in the nursery business. 



The most important economic result of the year, as regards 

 plant-diseases and insects, is the further demonstration of the 

 value of copper and arsenical sprays, and the popularizing of the Sprays, 

 necessity of spraying. It is now known beyond question, that 

 by far the larger number of injurious fungi and insects can be 

 practically and economically controlled by a proper spray, 

 and farmers themselves are now among the most ardent ad- 

 vocates of the practice. Paris green and London purple still 

 remain the most powerful weapons against most insects, with 

 the improved kerosene emulsions * still leading for the exter- 

 mination of plant-lice and similar insects. The United 

 States has led in the use of arsenical sprays, but the prejudice 

 against them in England is being overcome, and their use there 

 is extending. The demand for large quantities of Paris green 

 for fighting the cotton-worm has resulted in the adulteration 

 of the material in the South. Louisiana has enacted a law 

 for the protection of buyers, which requires that Paris green 

 must be sold upon a guaranteed analysis, as commercial fer- AduUera- 

 tilizers are sold. " Pure " Paris green must contain at least Paris 

 50 per cent, of arsenic ; all samples containing less than 50 & reert - 

 percent, are marked "impure." Every package sold is re- 



*See Bull. 76, Mich. Exp. Sta. 



