THE RUST MITE. 125 



stronger than are required for scale insects, or else make 

 several applications of washes competent to kill the mites 

 only. In this way the trees may be freed of mites, by 

 killing the young as they hatch, and not allowing any to 

 reach the adult stage and produce a fresh crop of eggs. 



The following substances have been tried and their ef- 

 fects noticed upon the mites and their eggs : 



Whale-oil Soap. The action of this substance upon the 

 mites is peculiar ; a trace of it in solution causes them to 

 relinquish their hold upon the leaf. All other liquids that 

 have been tried, even if they kill the mites, increase the 

 tenacity with which they cling to its surface. All the 

 free* mites are at once removed from leaves dipped in a 

 solution of one pound to one hundred gallons of water. 

 Stronger solutions are, however, required to kill them or 

 their eggs and the dormant (molting) young. 



The following experiments made in the laboratory upon 

 infested leaves show the action of solutions of various 

 strength. In order to retain the mites upon the leaves 

 the liquids were beaten into foam, which was spread evenly 

 upon both surfaces, care being taken to wet every part of 

 the leaf: 



Solution : One pound to five gallons. Adult mites all 

 killed ; molting mites apparently all dead. Eggs evidently 

 affected, not all killed, but many collapsed by the second 

 day. 



Solution : One pound to one gallon. (This solution is 

 nearly solid when cold.) Mites all killed. On the second 

 day all the eggs appeared collapsed and dead. 



The whale-oil soap usually supplied by dealers is inferior 

 to that used in the above experiments. As an effective 

 remedy for rust mite a solution of one pound to five 



*This term includes adults and young not dormant or undergoing trans- 

 formation. 



