7 



effective when used at the rate of 1 pound to 8 gallons of water. 

 Similarly in Massachusetts arsenate of soda gave good results 

 as a weed destroyer, either when used alone or when mixed with 

 corrosive sublimate in equal parts. 



EXPERIMENTS WITH ARSENITE OF SODA. 



Before giving an account of the experiments with arsenite of 

 soda at this Station and elsewhere in Hawaii, it may be well to 

 refer briefly to other experiments with the same chemical. In 

 Australia this spray has been widely used for the destruction of 

 prickly-pear, wild blackberry and other shrubby and herbaceous 

 weeds. For this purpose it has proven so effective as to make a 

 wide field for itself in the programme of weed destruction. 

 Maiden, 2 on the basis of a number of experiments, recommends 

 for destroying prickly-pear a solution of arsenite of soda con- 

 taining 1 pound to from 5 to 9 gallons of water. In other exper- 

 iments more concentrated solutions were used, particularly for 

 the destruction of wild blackberry and other shrubby weeds. 

 Likewise in Iowa, Xorth Carolina, Vermont, Massachusetts and 

 elsewhere on the mainland, as well as in Europe, arsenite of 

 soda has been used with good success in destroying miscellaneous 

 herbaceous weeds. In Massachusetts it proved effective when 

 used at the rate of 1 part to 66 parts of water. Kilgore 3 found 

 that when an attempt was made to combine arsenical insecticides 

 containing soluble arsenic with fungicides containing copperas, 

 copper sulphate or iron chloride, the burning effect of the arse- 

 nite was considerably increased by the presence of the other min- 

 eral salts.* In spraying experiments for the destruction of insects 

 Gillette 4 observed that soluble arsenites in arsenical sprays pro- 

 duced a greater burning effect in the presence of dew and direct 

 sunlight. These points are worth considering as indicating the 

 conditions under which applications of arsenite of soda should 

 be made in order to obtain a maximum effect. 



i Vt. Sta. Rept. 1901, p. 248. 



2Agr. Gaz. N. S. W. 9 (1898), p. 984. 



3 N. C. Bui. 77b. 



4 Iowa Sta. Bui. 10, p. 419. 



