88 BULLETIN 957, U. S, DEPAETMEISTT 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 ^® 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 bhster 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 H 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. 



=8 Martin, J. F., Gravatt, G. F., and Posey, G. B. Treatment of ornamental white pines infected with 

 blister rust. U. S. Dept. Agr. Cir. 177, 20 p., 12 fig. 1921. Seen in manuscript. 



