190 AN2?rAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



This study is now being carried forward to determine the age at 

 which Douglas fir becomes subject to extensive decay. The determi- 

 nation of this age will enable stands to be cut before there is any 

 appreciable loss and at the same time permit the trees to attain 

 maximum size. Equally important is the periodic rate of increase 

 in the loss through decay after this age has been passed. Such in- 

 formation will be of the highest value to the Government and to 

 holding companies with extensive stands of mature or overmature 

 timber, enabling them to estimate the loss in their holdings and to 

 adapt their plans accordingly. 



CHESTNUT BLIGHT. 



The southward spread of the chestnut blight has been steady, and 

 data have been accumulated to nnsvrer the very numerous questions 

 as to how much time it will take for the disease to reach a given 

 locality, in order that owners of forest stands and the industries of 

 that locality that are dependent on the chestnut may have time to 

 readjust themselves. The experiments on breeding resistant and 

 immune chestnuts continue, and search is being made for other re- 

 sistant or immune chestnuts, both in the United States and in other 

 countries. The most hopeful results obtained so far consist in the 

 discovery of certain surviving resistant American chestnut trees, 

 which are being propagated. 



WHITE-PINE BLISTER RUST. 



White-pine blister rust is a destructive plant disease that reached 

 America about 1900: it was introduced from Europe on infected 

 white-pine nursery stock which w^as planted in many places in the 

 eastern United States. The l)lister rust was first observed on cur- 

 rants at Geneva, N. Y., in 1906, and three years later was discovered 

 on planted white pines. In 1913 it was found attacking native white 

 pines, but its wnde distribution was not suspected until the late fall 

 of 1915. wdien the rust was discovered on currant and gooseberry 

 bushes and white pines over a large area in Massachusetts and New 

 Hampshire. Up to this time efforts had been made to stamp out the 

 disease in pine plantations where it was known to be present. This 

 policy was abandoned in the East when general scouting in 191G 

 showed that the disease was widespread on native host plants in the 

 Northeastern States. As a result, experimental control work Avas 

 begun in 1917 in cooperation with the affected States in the hope of 

 developing practical methods of control which would assure the 

 continued production of the white-pine crop. 



Since then practical measures have been developed for the control 

 of this disease under eastern conditions, consisting of the eradication 

 of currant and gooseberry bushes within 900 feet of the pines. Con- 

 trol measures can be applied by pine owners at a cost suflficiently low 

 to justify their general application, and any stand of white pine, 

 large or small, can be adequately protected. 



In the Eastern States there ^are more than 21,000,000,000 board 

 feet of white pine, estimated to be worth $276,000,000, as well as a 

 very large acreage of young growth. In many sections white pine 

 is an important farm crop, providing a source of ready money, keep- 



