108 



Laundry Soap. 



Experiment 16. — Three applications of strong solutions of laundry 

 soap were made with a brush to infested leaves, from the 19th to 

 the 22d July, with the effect . to destroy all the bark lice, occa- 

 sionally, however, with trifling damage to the leaves. The effect of 

 these applications apparently differed but little from those of the 

 whale oil soap. 



PyretJtrinu. 



Experiment 17. — Although expecting nothing from the application 

 of pyrethrum, we made a few experiments with it, commencing July 

 19. As they were all entirely ineflcient, the results need not be 

 given further than to say that the fresh pyrethrum powder suspended 

 in water in quantities varying from a tablespoonful to the gallon up 

 to an excessive proportion was applied by brushing and dipping, 

 without any effect whatever. Pure pyrethrum was also dusted upon 

 the leaves without result. 



Carbolic Acid. 



Experiment 18. — July 19, leaves infested with the young bark lice 

 were thoroughly wetted with carbolized water (a teaspoonful of the 

 pure liquid acid to the gallon) and examined hve hours later. The 

 bark lice were all alive. This experiment was twice repeated, both 

 in the laboratory and the field, with only negative results. 



A few additional experiments were made with tobacco water (one- 

 half pound tobacco to a gallon of water) ; with hellebore (one ounce 

 to the gallon) ; and with a weak solution of caustic soda, — in all 

 cases without any favorable result, every individual being apparently 

 alive in from one to three days after treatment. 



As a general result of the above series of experiments we may 

 say that a kerosene emulsion diluted with soap suds to a strength 

 of from two and a half to five per cent., was found effective during 

 the month of July and did not injure the leaves. This was the 

 only substance experimented with which gave any promise of use- 

 fulness, with the exception of the whale oil and soaps, which were sub- 

 ject to the drawback already mentioned ; that is the liability to injure 

 the leaves if used in a solution strong enough to destroy the bark 

 lice. Possibly if it were washed off shortly after application, as 

 recommended by Dr. Lintner, the injurious result might be pre- 

 vented, but this would too greatly increase the trouble and expense 

 of the application. 



Washing off the Females and Egg Masses with Water. 



From correspondents in Northern Illinois, I learned that late in 

 June, the practice became somewhat general of washing off the egg 

 masses and the outworn bodies of the females with jets of water 

 from the hydrants, throwing the water into the tree by means of a 

 hose, but I have not yet been able to learn Avith what result. 

 This method was, apparently, usually applied under the mistaken 



