Feb. lo. 1919 Injury to Casuarina Trees 1 63 



killed by spraying the affected part of the trunks with poisoned kerosene 

 emulsion ^ made in accordance with the following formula, recently 

 revised by Mr. F. C. Craighead : 



Standard miscible oil pint i 



Water gallons 5 



Sodium arsenate poimd .... X 



Dissolve the arsenate in water, stir, then add i pint of miscible oil. 



From April to June, when large numbers of the adult beetles are flying 

 and feeding on the bark, they should be killed by spraying the tree 

 trunks with the poisoned kerosene emulsion. 



No pruning of casuarina trees should be attempted between April 

 and August, since the consequent flow of sap will attract the flying 

 beetles to the trees. 



Mangrove stakes should not be used to support young, recently set- 

 out trees, as they will attract the borers. 



According to the host-selection principle ^ as advocated by Dr. A. D. 

 Hopkins, the beetles that breed for one or two generations or more in the 

 casuarina will be much more likely to reinfest this host than they are to 

 go back to the original host; and, since the beetle became established in 

 the mangrove before the casuarina was introduced, it is to be expected 

 that only occasional individuals, among the thousands of beetles that 

 breed in the mangrove, will deposit eggs on the casuarinas. It is of 

 primary importance, therefore, to keep as many of the beetles as possible 

 from reaching maturity in the casuarinas. 



1 Craighead, F. C. a new mixture for coNTRoi,LrNG wood-boring insects — sodium arsenate 

 EMULSION. /« Jour. Econ. Ent., V. 8, no. 6, p. 513. 1915. 

 * U. S. Department OF Agriculture, program of work [igibj/igij, p. 353. Washinfiton, 1916. 



