78 The Spraying of Plants. 



ation of insecticides which destroy the organism, not by enter- 

 ing its body with the food, but by penetrating the outer cover- 

 ings directly, and causing the death of the insect only after the 

 material has come in contact with some vital part. There are 

 several materials which possess this power, and some of them 

 have long been in use. Strong alkalies, such as potash or soda, 

 were among the first substances employed for this purpose. 

 The insectidal value of soap is largely due to alkalies which 

 have commonly been applied in this form. The intrinsic value 

 of all soaps has caused them to be used as the foundation 

 for many mixtures. Quassia wood contains an alkaloid which 

 is fatal to insect life, and decoctions of the " chips " have been 

 recommended since the early part of this century. Pyrethrum, 

 kerosene, and resin can also be added to the list, although 

 their value has not been known, in all cases, so long as that 

 of the materials mentioned above. 



Pyrethrum first attracted the attention of Europeans early in 

 this century. 1 It had long been sold by the people living south 

 of the Caucasus Mountains in southeastern Asia, the plant 

 being a native of the district. An Armenian named Juintikoff 

 learned that the powder was obtained from the flow r er heads of 

 certain species of pyrethrum, and in 1828 his son began to 

 manufacture the powder on a larger scale. It was exported, 

 and at present this industry brings large revenues into the 

 countries in which it is carried on. The species which furnishes 

 the best powder is Pyrethrum roseum (properly Chrysanthemum 

 coccineuni) ; it is not cultivated in Asia, but the flowers of the 

 wild plants are gathered. The Dalmatian powder is produced 

 from Pyrethrum (or Chrysanthemum) cineraricefolium, a closely 

 related species. About 1850, pyrethrum powder was introduced 

 into France for the destruction of insects in houses. In 1856 

 good seeds were obtained from the Caucasus, and these having 

 been planted, a crop of home-grown seed was secured two 

 years later. Plants of Pyrethrum roseum were grown in 

 America as an ornamental plant at least as early as 1870 ; 

 but the Dalmatian form has been grown for the purpose of 

 producing the highly prized powder. The first to engage in 



1 See U. S. Patent Office Sept. Agrie. 1857, 129 ; Ibid. 1861, 223 ; and Ann,. 

 Kept. U. S. Com. of Agric. 1881-82, 76. 



