DESTRUCTION OF FLY LARVH IN HORSE MANURE. 21 
Plant material containing alkaloids— 
‘‘Black leaf 40’’—tobacco extract (Nicotiana tabacum). 
Larkspur (Delphinium). 
Stramonium (Datura stramonium). 
Hellebore ( Veratrum album and Veratrum viride). 
Other plant material— 
Oxeye daisy (Chrysanthemum leucanthemum). 
Pyrethrum (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. 
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