DESTRUCTION OP FLY LARV^ IN HORSE MANURE. 23 



effects of large applications of boron upon the growth of plants, as 

 shown by several investigators. In this connection it is important 

 to note that investigations of Kussell and Buddin (1913) in Eng- 

 land have shown that the application of very small amounts of vola- 

 tile and some nonvolatile disinfectants have eventually resulted in 

 the stimulation of plant growth. This same effect is indicated in 

 some of the experiments with borax. 



In the field and pot experiments no deleterious effects were ob- 

 served from the application of borax at the rate of 0.62 pound per 8 

 bushels (10 cubic feet) of manure, except possibly on wheat. Larger 

 doses of borax produced a discoloration of the tips of some other 

 plants. In our field experiments with winter wheat the plants when 

 4 inches high showed a decided yellowing of the tips where very 

 heavy applications of borax were made, but at the start of the 

 growing period in the spring the yellowing of the tips decreased and 

 the wheat was nearly normal in appearance. These effects vary with 

 the plants and the amount of moisture present in the soil. Where 

 rainfall is heavy the effects disappear quickly. At Orlando, Fla., 

 for instance, where the experiment was conducted during a drought 

 and larger amounts of borax than 0.62 pound per 8 bushels were 

 used, injurious effects were much more evident than in other 

 localities. In all these cases, however, except at Orlando, recent ob- 

 servations have shown that the plants have practically recovered — 

 so far as can be determined without estimating the actual yields, 

 which can not be done at the present time. From these experiments 

 it is believed that no injurious effects will follow the application of 

 the minimum amount of borax found necessary to destroy the larvae, 

 namely, 0.62 pound per 8 bushels of manure, which may be applied 

 to the field at the rate of 15 tons per acre. If more is necessary, 

 untreated manure may be used. Some recent pot tests have indicated 

 that the addition of slaked lime in amounts equal to half that of the 

 borax present tends to offset the toxic action which results from heavy 

 applications of borax. Some questions relating to the effects of borax 

 on the growth of plants remain to be determined, notably its possible 

 cumulative action, and these will be reported later. 'It is expected 

 that interesting results will follow from the experiments now under 

 way with calcined colemanite, which, though cheaper than borax, is 

 effective in destroying fly larvae when applied at the rate of 0.75 

 pound per 8 bushels. 



SUMMARY. 



CLASSIFICATION OF CHEMICALS TESTED. 



The substances used in the experiments dealt with in this bulletin 

 may be arranged in two classes, as indicated below. The term 

 "satisfactory" is used to indicate destructive action on fly larvae, 



