28 PROTECTION' OF PLANTS. 1916-17 



CARRIERS AND DILUENTS FOR DUSTING 



C. E. Fetch, Hemmingford, Que, 



During the past five or six years experiments have been performed 

 comparing the dust and liquid methods of applying insecticides and fungi- 

 cides. Last year this work increased enormously and good results were 

 obtained, but there are still many objections to dusting to be overcome. 



It is too early to say whether sucking insects, such as aphids, can be 

 destroyed by dusting, but experiments have shown this method to be equal 

 to or better than liquid sprays for most biting insects. One serious objec- 

 tion to dusting is the cost of materials, and it was chiefly this objection that 

 caused me to make this preliminary study of carriers and diluents. 



Dusting should be very valuably in the control of most shade-tree 

 insects, and also on many occasions in orchards when only an insecticide is 

 necessary. Therefore, it can be readily seen that a good carrier and diluent, 

 at a small cost, is a very important item. Carriers should be nearly of the 

 same specific gravity as the insecticide and fungicide used, otherwise upon 

 standing the heaviest material will settle down in the containers. It will be 

 seen in the following table that the source of carriers is a local one in many 

 cases and the grower can gather and prepare his own. 



Basing conclusions solely upon the notes in the following table, the best 

 diluents and carriers are, in the order of efficiency, — talc schist, limestone, 

 gypsum, china cla/ and silt. 



