DESTRUCTION" OF FLY LARViE IN HORSE MANURE. 21 



Plant material containing alkaloids — 



"Black leaf 40" — tobacco extract {Nicotiana tubacum). 



Larkspur (Delphinium). 



Stramonium (Datura stramonium). 



Hellebore ( Veratrum album and Veratruin viride) . 



Other plant material — 



Oxeye daisy (Chrysanthemum leucanthemum) . 

 Pyretbrum (Chrysanthemum cinerariaefolium). 



Powdered hellebore proved the most efficient and practical of all 

 the substances tested. 



COMPARATIVE ADVANTAGES OF BORAX AND HELLEBORE. 



Borax, which was shown in Bulletin No. 118 to be an effective 

 larvicide, is obtainable in all parts of the country, and the cost of 

 treating manure at the rate of 0.62 pound of borax per 8 bushels is 

 0.42 cent per bushel. 



Powdered hellebore, using one-half pound to 10 gallons of water 

 and applying this to 8 bushels of manure, is also an effective larvicide 

 and exerts no injurious action on the fertilizing value of the manure 

 as determined by bacteriological and chemical analyses, and no 

 injurious action on plants has been detected in any of the field tests. 

 Hellebore is used as an insecticide and is obtainable in most cities and 

 agricultural districts. The cost of this treatment is 0.69 cent per 

 bushel of manure. 



While borax may be applied to manure at the foregoing rate and 

 the treated manure may be added to the soil at the rate of 15 tons to 

 the acre without injuring vegetation, nevertheless excessive quantities 

 of borax may be applied to manure through carelessness, and injury 

 to vegetation may in consequence result. In the light of this year's 

 experiments it seems advisable to recommend borax as a larvicide for 

 the treatment of outhouses, refuse piles, and all other places where flies 

 may deposit eggs. However, on account of the possible carelessness 

 previously mentioned, and because large quantities of manure are 

 sometimes used by truck growers, it seems best to guard against pos- 

 sible injury to vegetation by recommending powdered hellebore for 

 the treatment of manure, since no injury can arise from the use of 

 excessive quantities, as it is entirely decomposed in the course of 

 the fermentation of the manure. 



