476 Report of the Entomologists of the 



Pyrethrum. — This is sold under the name of "Persian in- 

 sect powder " or " buhach." It is a valuable insecticide and is 

 especially adapted for use against plant lice and similar insects. 

 It is one of the most powerful contact poisons and may be applied 

 pure or mixed with two or three times it® own bulk or diluent. 

 When used in this way it is especially adapted to small con- 

 servatories. 



Pyrethrum has also been used with kerosene emulsion either 

 as a kerosene extract or mixed directly with the emulsion. 



Hot water has been successfully used against plant lice. Its 

 use is considered practical only on a small scale. Most plants 

 will not be injured by the application of water heated to 130° F. 

 This treatment is fatal to the lice. Where practical, the whole 

 plant may be dipped. 



EXPERIMENTS AGAINST PLANT LICE. 



Spraying Experiments with Whale-oil Soap. 



These experiments were conducted in the Station plum orchard 

 and in the garden on red currant bushes. The principal object 

 of the experiments was to demonstrate whether whale-oil soap 

 could be depended upon to check plant-lice when used as a spray, 

 and thus avoid the necessity of preparing kerosene emulsion. 

 Both the plum trees and currant bushes were badly infested, the 

 former principally with Hyalopterus pruni and the latter with 

 Myzus rihis. Both of these species are treated in detail on sub- 

 sequent pages. The currants were sprayed first as follows: 



On May 15, with a solution of whale-oil soap, 1 pound to 10 

 gallons of water. Although much pains was taken to apply the 

 spray so as to reach all of the lice, there was but little noticeable 

 effect from the application. 



On May 30 the currants were again sprayed but with a stronger 

 solution of soap, 1 pound to 7 gallons of water. The leaves were 

 badly curled, but by drenching them with the spray directed from 

 below most of the lice were reached. The effects of this applica- 

 tion were soon apparent. 



