Many devices for protecting trees from rabbits have been recommended,
the majority of which are paints, smears, or washes supposed to be
distasteful to the animals. Many are not sufficiently permanent to
afford protection for an entire winter, and most of those that are
lasting are injurious to trees. Coal tar, pine tar, tarred paper, and
oils, under certain conditions, are dangerous to young trees. Carbolic
acid and other volatile substances afford only temporary protection, and
must be renewed too often to warrant their use. Bitter substances, like
commercial aloes and quassia, are useless against rabbits.
The most promising simple washes for protecting large trees from rabbits
are those containing lime mixed with sulphur or copperas in various
combinations. Lime alone is not sufficiently permanent, especially where
much rain falls. When mixed with sufficient copperas it has a deep green
color and sticks much better. The lime-sulphur wash commonly used to
destroy San Jose scale in winter has often proved successful as a rabbit
repellent, but its lack of adhesive qualities often makes it fail. The
defects may be partly corrected by mixing salt, soap, or a cheap glue
with the lime and sulphur while the wash is still hot.
A poisoned wash of starch and glycerin, tried during the winter of
1913-14 in Idaho by a field agent of the Biological Survey, gave
excellent results in protecting young orchards from jack rabbits, and
would probably be equally effective where cottontails are concerned. The
wash is prepared as follows:
Dissolve 1 ounce of strychnine (sulphate) in 3 quarts of boiling water.
Dissolve 1/2 pound of laundry starch in 1 pint of cold water. Pour the
starch into the vessel containing the strychnine and boil the mixture a
short time until it is clear, adding 6 ounces of glycerin and stirring
thoroughly. When it is cool enough apply with a paint brush to the tree
trunks.
The glycerin and starch adhere well and form a thin coating to the bark.
Rabbits attacking the trees will be quickly killed. In the Idaho
experiments none of the trees were damaged badly enough to affect their
growth and all the rabbits in the orchards were destroyed. The method is
well worth trying; but ~care should be taken not to endanger domestic
animals~.