THE WHITE-PINE BLISTER RUST SITUATION 



137 



structures should not consider anything other than 

 high-class grades. A shingle need not be absolutely 

 clear to be first class. It might have minor defects 

 in the tip without injuring the grade of the shingle one 

 iota, but it should be free from sap and practically ver- 

 tical grain. It is like throwing cold water in the face 

 of the word "conservation" to advocate the use of only 

 absolutely clear shingles. There is a use for all grades 

 of shingles and the greatest task that the manufacturer 

 has today, in order to put his business on a permanent 



foundation, is to educate the consumer on the proper 

 grades to use on the proper place. 



The shingle manufacturers also have another very 

 important task on their hands to correct the false impres- 

 sion on the part of the general public regarding the fire 

 risk of shingles. This impression is largely due to com- 

 petitors of wooden shingles. 



The cedar tree does not claim preeminence where 

 strength is required, but it does claim unexcelled recogni- 

 tion for durability and lightness. 



The White -Pine BHster Rust Situation 



By Dr. Perley Spaulding 

 Pathologist, U. S. Department of Agriculture 



IN Americ.\x Forestry for February attention was 

 called to the serious disease of white pines which 

 was introduced some years ago from Europe. A col- 

 ored plate was also printed showing the different stages 

 of this disease upon white pines and the leaves of cur- 

 rants and gooseberries. Herewith is a diagram indicat- 

 ing the complete life history of the parasite causing this 

 disease. The arrows show the transfer of the disease 

 from one plant to the next. 



Figure 1 is the spring stage of the disease as it breaks 

 out upon the infected white pines. Immense numbers 

 of very minute dustlike yellow spores (seeds) are pro- 

 duced upon the pine. These are blown about by the 

 wind and fall upon the leaves of any currants or goose- 

 berries that may be in the vicinity. On these leaves, 

 Figure 2, they germinate and send the root into the 

 soft portions of the leaf. Two weeks later a second 

 crop of spores is produced upon the leaf. The disease 

 then may do one of two things — it may produce a second 

 generation of the same kind of spores, as indicated in 

 Figure 3, or there may be produced a distinct form of 

 disease as shown in Figure 4. 



The form shown upon Figures 2 and .3 may be called 

 the yellow summer stage. This is capable of repeating 

 itself every two weeks until the end of the season. This 

 is the stage where the disease spreads rapidly upon cur- 

 rants and gooseberries. It is very easy to see that if 

 the disease advances 200 feet with each generation of 

 spores produced, by the end of the season it may have 

 progressed a very considerable distance from the pine 

 which started the disease early in the spring. The brown 

 autumn form of the disease shown in Figure 4 may be 

 found from the latter part of July until the leaves have 

 fallen. Upon the rather stout brown hairs is produced 

 a third form of spores. These spores in turn, instead 

 of spreading the disease upon currants or gooseberries 

 are able to attack only the young bark of white pine. 

 In this way the complete life cycle of the parasite from 

 pine to currant or gooseberry and then back to white 

 pine takes place during a single summer. The disease, 

 however, does not show upon the newly infected white 

 pines until one or more years later. 



Any planting of white pine done from this time onward 



should be made with trees secured under the following 

 conditions. The person supplying them should be 

 required to furnish a written guarantee that his stock 

 fulfills the following conditions: 



DIAGRAM SHOWING PROGRESS OF WHITE PINE BEISTER 



RUST 



No. 1. The pine infected with the blister rust, showing condition as 



found in the spring. 

 No. 2. The currant, or gooseberry, leaf, showing the second stage of 



the disease, resulting from infection with the spores from a pine. 

 No. 3. Currant or gooseberry leaf, showing second generation of second 



stage of the disease, the result of infection of spores from currant or 



gooseberry leaves. 

 No. 4. The third spore stage on currant and gooseberry leaves, the 



condition being that in which it is transmitted to the pine trees. 



