86 



SOME INSECTS INJUKIOUS TO TRUCK CROPS. 



soap and 1 gallon of kerosene to 25 gallons of water; resin, 1 pound 

 to 16 gallons of water; and black leaf tobacco extract, 1 gallon to 65 

 gallons of water. Of these Mr. Qnayle says that the last seemed most 

 effective, with kerosene emulsion next, and that none of these sprays 

 in the given proportion injured the foliage at all. 



It Is entirely possible to kill most of the beetles well hit by the spray, but 

 many escape between clods in the soil or are protected by the vine or are con- 

 cealed in the growing tip. The percentage killed, however, will be satisfactory, 

 but this [treatment] must be repeated so often that the operation becomes 

 laborious and costly. 



While kerosene emulsion and whale-oil soap are practically never 

 advised as standard remedies for nrandibnlate or chewing insects, 



Fig. 18. — A cl•(_■^^ -^pia.MiiL; liop^ lu lU'itij^li Columbia. (Original.) 



such as this flea-beetle, both are employed in the infested terri- 

 tory against the hop aphis, or " louse," and therefore the hop grower 

 is familiar with their preparation and use. It has been ascertained 

 that when these are used against the hop aphis the flea-beetles coming 

 into contact with the emulsion are killed. The probabilities are that 

 kerosene emulsion properly prepared and applied in the affected 

 regions will be considerably less expensive than a tobacco extract, and 

 it is po.ssible to make a tobacco extract which woidd be comparatively 

 cheap. In recent experiments made under the writer's direction at 

 Norfolk, Va., whale-oil soap, used at the rate of about 1 pound to 10 

 gallons of water, emjjloyed against aphides, has proved quite as ef- 

 fective and as economical as kerosene emulsion, considering the fact 



66— VI 



