62 AN ECONOMIC STUDY OF FIELD MICE. 



gallon quantities) and is easily applied to the trunks of trees either 

 in the form of a spray or by the use of a brush. One thorough appli- 

 cation in November would probably be effective for the entire winter. 

 The ingredients of the wash are 20 pounds 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 be 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 sIioavs trees 

 5 inches in diameter which were completely girdled by mice in 

 December, 1903. Soil was heaped about the trunks in January, 1904, 

 and allowed to remain until May. 1905, 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 may 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 



o See Yearbook U. S. Dept. of Agriculture, 190G, pp. 429^46, Lime-sulphur 

 Washes for the San Jose Scale. 



