88 BULLETIN 957, U. S. DEPARTMENT OF AGRICULTURE. 
previous inspections. This makes the cost of the work prohibitive; 
and the disease progresses in spite of it. 
REMOVAL OF DISEASED PARTS AND DISEASED PLANTS OF PINES. 
The removal of diseased parts of infected pines does not appear to 
be an economical procedure from the viewpoint of the lumberman or 
wood-lot owner, because of the low value of single trees. For highly 
valued ornamental trees it becomes possible financially. Under such 
conditions, the removal of all Ribes to prevent new infecton, accom- 
panied by careful cutting out of all infections in the pines for several 
years, will finally result in the elimination of the disease from those 
trees. Martin, Gravatt, and Posey 58 have investigated the possi- 
bilities of this type of work. They conclude that — 
Experimental and practical results show that ornamental pines which have already 
become diseased can be saved by cutting out the infected parts if treatment is applied 
in time. The work is easily performed at a comparatively low cost. Treatment can 
be given any time during the year, but best results will be obtained from April to June 
when the cankers are more easily found because of the bright orange-yellow blisters. 
Successful treatment depends primarily upon ability to find the cankers and deter- 
mine accurately the edge of the diseased area. The workmen should be thoroughly 
familiar with the symptoms and appearance of the disease on pines. 
Where the Ribes can not be thus eradicated, other species of trees 
should be planted to take the place of the white pines. Cutting out 
infections depends, for success, on finding all of them. The work- 
man must be familiar with the blister rust and be thorough or the 
results will not justify the cost. If a tree is nearly girdled near the 
ground, or if most of the branches must be removed, it is useless to 
attempt to save it. The cutting out must be repeated for several 
years after all the Ribes are eradicated, as dormant and slightly 
developed infections become visible. Cutting out experiments 
showed that cutting back for 1^ inches or more from the extreme 
edge of the infected area insured removal of all diseased bark and stop- 
ped the disease in those areas. In practice this distance should be 
increased to 5 or 6 inches to insure thorough work. 
On a main trunk an infection which has extended only part way 
around the trunk may be treated by peeling off the bark on the canker 
and to the required distance around it. In this case the safety zone 
should extend for 4 or 5 inches directly above and below the diseased 
area but need not extend more than half as far sidewise. 
The removal of only diseased white pines in infected imported 
trees has been inefficient and costly, even where the Ribes were 
removed too. Records of such work in about 900,000 imported trees 
(136) shows that it is inefficient, although the disease has been checked 
somewhat. The cost has been great enough to have replaced the 
imported trees with healthy home-grown ones. 
58 Martin, J. F., Gravatt, G. F., and Posey, G. B. Treatment of ornamental white pines infected with 
blister nist. IT. S. Dept. Agr. Cir. 177, 20 p., 12 fig. 1921. Seen in manuscript. 
