62 AN ECONOMIC STUDY OF FIELD MICE. 
gallon quantities) and is easily applied to the trunks of tree- either 
in the form of a spray or by the use of a brush. One thorough appli- 
cation in November would probably he effective for the entire winter. 
The ingredients of the wash are 20 pound- of unslaked lime. 15 
pounds flowers of sulphur, and water to make 45 to 50 gallons. The 
mixture should be boiled in an iron kettle at least an hour and applied 
to the trees while warm." 
Winter mulching of trees is dangerous, unless the neighborhood is 
known to be free from mice. Mulch containing straw may lje placed 
in the orchard in spring, but it should be removed before the approach 
of cold weather. Fine, thoroughly rotted manure may be used in the 
orchard with but little danger. Lime or ashes about the trunks of 
trees has some value in keeping off mice, but clean cultivation is 
equally or more effective. 
REMEDIES FOR INJURED TREES. 
When trees are girdled by mice, portions of the inner bark 
(cambium layer) are often left, partly covering the hard wood 
below. If sunlight and wind have free access to the injury, the 
remaining bark dries up and the tree dies. If light and air are 
excluded, new bark will form and the wound quickly heal over. To 
facilitate the healing process, it is important that wounds be covered 
as soon as possible. As a covering for wounded trees, wax. paint, 
strips of cloth, clay, and cow dung have been recommended, but 
none of them has any advantages over fresh, loose soil. Unless the 
ground is frozen, this is always available and easily applied to 
wounds near the ground. All that is needed is to mound up the 
soil about the trunk of the tree high enough to cover the wound. 
Allowance should be made for settling of the soil, and the covering 
should remain during the entire summer. Plate VIII shows trees 
5 inches in diameter which were completely girdled by mice in 
December. 1003. Soil was heaped about the trunks in January. 1004, 
and allowed to remain until May, 1005, when it was removed and 
the photographs made. Xew bark completely covered the wounds, 
leaving slight visible scars. 
If large fruit trees are injured high up. as sometimes happens 
when snow is drifted about them and mounding up the soil is imprac- 
ticable, there are other means of saving them. If the injury is not 
too extensive, grafting wax should be applied to the wounds and the 
tree wrapped with strips of cloth. If. however, the cambium be 
eaten through over considerable surface, bridge grafting mav be 
resorted to. 
Bridge grafting is not difficult. It consists in bridging over the 
girdle of eaten bark by means of scions or small twigs of the same 
kind of tree. The injured bark at the top and bottom of the wound 
should be cut back to live, healthy tissue and small clefts or notches 
See Yearbook U. S. Dept. of Agriculture, 1000. pp. 420-140. Lime-sulphu* 
Washes for the San Jose Scale. 
