2(')() HKl'OHT OF OFFICE OF KXI'EHIMENT STATIONS. 



suflioiciit to protect Into oal)l)afro :iiul {aulinowor from an attack of the 

 (•al)l)a«ii' woj'iii and (•al)l)a«;c loojx'r. In addition to this iiisocticidal 

 value it apjH'arcd to increase the yield of cahhap' from (lO to 100 per 

 cent. It is reconnnended tliat it shoidd not he used on cal>l)a<re after 

 the heads are two-thirds formed, nor on caulillower after the flower 

 has becomt' exposed. Tiie cost of two applications j^er acre was 

 about >t^"J. 



Nnnu>rous cxj)eriments have been undertaken to determine the 

 value of dust spraying. This method has been used in Missouri and 

 elsewhere on fruit trees and is in general use in the Southern States in 

 lieatin<; cotton. 



In Delaware" favorable conditions were found for using the dust 

 method for the reason that heavy dews may be ex])ected during the 

 season for the apj[)lication of insecticides. The best results were 

 obtained in a test of dust spraying in the nse of a mixture of pulver- 

 ized (•oj)i)er sulphate, hydrated lime, and an arsenical poison, either 

 Paris green or arsenate of lead. It was found that about 2 iK)unds 

 of the dry mixture Avere re(}uired to spray an amount of foliage which 

 would be covered by 4 gallons of liquid mixture. From the experi- 

 ments carried on in Delaware, however, the dust si)raying under 

 favorable conditions should not cost more than one-half as much 

 as liquid spraying. In these tests five applications were made before 

 the buds began to swell and others in May and June, the work being 

 done early in the morning so as to get the benefit of the dew. The 

 dust spray was applied to apple, pear, peach, plum, and cherry trees. 

 Some of these trees showed the presence of fungus diseases and others 

 not. No injury was observed on peach trees from the application of 

 this method. As compared with liquid spraying it was found that 

 the trees sprayed Avith a dust insecticide failed to hold so large a 

 percentage of fruit. Codling moth and apple scab were satisfac- 

 torily controlled by dust spraying. 



SOAP INSECTICIDES. 



The New York State Station ^ undertook the study of the composi- 

 tion of certain commercial soaps as related to their use in spraying. 

 It has been found that commercial whale-oil soaps in many cases 

 failed to destroy insects and sometimes were injurious to the foliage. 

 It appears from these experiments that the important constituents of 

 these soaps, in so far as their insocticidal use is concerned, are water, 

 actual soap, and free alkali. In samples of commercial whale-oil 

 soap analyzed by the station, the amount of w^ater varied from 11 to 

 55 per cent, that of soap from 15 to 60 per cent, and that of free 

 alkali from to 1.3 per cent. In one instance two lots of soap from 



o Delaware Sta. Bui. 69. » New York State Sta. Bui. 257, 



