Of the numerous substances tried, the one which seems best to fulfill
these conditions is powdered hellebore.[10] For the treatment of manure a
water extract of the hellebore is prepared by adding 1/2 pound of the
powder to every 10 gallons of water, and after stirring it is allowed to
stand 24 hours. The mixture thus prepared is sprinkled over the manure
at the rate of 10 gallons to every 8 bushels (10 cubic feet) of manure.
From the result of 12 experiments with manure piles treated under
natural conditions it appears that such treatment results in the
destruction of from 88 to 99 per cent of the fly larvæ.
Studies of treated manure indicated that its composition and rotting
were not interfered with. Furthermore, several field tests showed that
there was no apparent injury to growing crops when fertilized with
treated manure.
Since the solution is somewhat poisonous it should not be left exposed
where it might be drunk by livestock. It is quite safe to say that
chickens will not be injured by pecking at hellebore-treated manure.
This has been tested carefully. Hellebore can be obtained both in ground
and powdered form, but the powder gives the best results in the
destruction of fly larvæ.
[Footnote 10: _Veratrum viride_ or _V. aloum_.]