1921.] PUBLIC DOCUMENT — No. 31. 39 a 



lowed until the necessity for a chanfije became evident. As a 

 repellent against ants, it killed a few which were actually hit 

 by the material; the others were not affected, nor was the 

 prosperity of the colony as a whole checked perceptibly. 

 Grass and other plants around the nests were killed. Against 

 squash bugs it showed no repellent value and did not kill the 

 eggs. It killed the young bugs, but when used strong enough 

 to do this it killed the squash leaves also. Against mites on 

 evergreens it proved fairly effective, but when any large per- 

 centage was killed, its strength had been necessarily increased 

 to a point where it was not safe for the leaves. In the case 

 of plant lice the strength recommended proved dangerous to 

 the foliage of the plants, though killing the lice. Further tests, 

 diluting the material at the rate of 1 to 60, and even 1 to 

 70, gave excellent results with the insects and no leaf injury. 



Mixed w^ith arsenate of lead the same results were obtained, 

 and the conclusion was finally reached that Sulco V. B., at 

 the strength recommended by its makers, is unsafe for use 

 on most kinds of foliage; and that, when diluted to a point 

 where it will not cause foliage injury, it is ineffective as an 

 insecticide except for plant lice. For these pests, however, it 

 can be diluted to a point where the leaves will not be injured 

 and still kill the insects. 



White Arsenic as an Insecticide in Bordeaux Mixture. — Some 

 recent experiments, reported by Sanders and Kelsall (Proceed- 

 ings of the Entomological Society of Nova Scotia, No. 5, for 

 1919), using arsenic instead of arsenate of lead or arsenate of 

 lime in Bordeaux mixture, made it seem desirable to give a 

 little attention to this subject. White or commion arsenic 

 costs less than the other arsenicals, "is the most concentrated 

 form of arsenic, and consequently suffers least from freight 

 rates, occupies less space, and entails the handling of less 

 weight." If it can be used as safely and effectively as the 

 other insecticides in combination with Bordeaux mixture, it 

 should largely replace them, at least for some purposes. 



Tests of this mixture on potatoes were made during the 

 season, a very finely divided sample of arsenic being used. To 

 prepare 50 gallons of the spraj", half a pound each of white 

 arsenic and fresh, unslaked lime were used. The lime was 

 slaked in just enough water to keep the action brisk, and the 



