APPENDIX. 



403 



can be applied without damajje to trees. (2) All wild plum trees in the 

 woods through a hop-g-rowing- country should be destroyed. (3) The hop 

 vines should be either burned or thoroughly drenched with kerosene emul- 

 sion as soon after the crop is harvested as possible with a view of killing the 

 males, and thus preventing the impregnation of the females. If these 

 measures are carefully followed, comparative exemption from lice may con- 

 fidently be expected. 



Fig. .'i — Tho ITop Phint-louse, male — enlarged. 



At the present time it is too late for preventive work, and the only thing 

 which can be done to lessen the damage to the crop is to destroy the lice 

 upon the vines by spraying with an insecticide mixture. Such spraying can, 

 with care, be made quite effective, and the individual hop grower will have 

 the satisfaction of knowing that whatever work he does upon his own yard 

 will not be thwarted by the carelessness of neighbors, as during the summer 

 the lice can not migrate except bj^ crawling from one yard to another. 



Substances to be used — Of all the different substances experimented with 

 in 1888 none gave better satisfaction than properly prepared kerosene emul- 

 sions and fish-oil soaps. 



FORMULA FOR KEROSENE EMULSION'. 



Cheap kerosene 8 pints 



Water 4 pints 



Soap OA pound 



Dissolve the soap in the water and add ( boiling hot j to the kerosene. 

 Churn the mixture by means of a force-pump and spray-nozzle for five or ten 

 minutes. The emulsion, if perfect, forms a cream which thickens upon 

 cooling, and should adhere without oiliness, to the surface of glass. Dilute 

 one part of the emulsion with twenty-five parts of water. 



