92 



ing in the crevices, or the characteristic inner bark. The most evi- 

 dent danger signal, however, is the v^^ilting of the leaves upon 

 branches v^hich have been girdled by the blight. As soon as the 

 branch or tree is girdled the passage of v^^ater from the roots of the 

 tree is shut off and the leaves begin to droop and soon take on their 

 autumnal coloring. While a branch bearing v^^ithered leaves is not 

 conclusive evidence that a tree is infected with the blight, such 

 branches demand a closer inspection, and in the vicinity where the 

 blight is working are nearly always caused by the disease. In the 

 winter the same signal is observed in the withered leaves and un- 

 developed burrs which persist on certain trees or branches. It has 

 been found by our men that they can cover more ground and do bet- 

 ter work after the leaves fall than in the summer, because the light 

 shows up the cankers along the trunk, and the unusual branches, 

 leaves and burrs are seen more clearly. Under a canker usually 

 appear sprouts which are caused by the daming of the sap which is 

 deflected to the growth of such sprouts. A small cluster of sprouts 

 along the trunk of a tree is unusual unless the blight is at work im- 

 mediately above. Further investigation will show whether or not 

 this is the case. 



All of these features can be seen in the display and a careful 

 examination of them will make any man competent to look over 

 his timber and determine very closely the amount of infection on the 

 trees. 



The Bureau of Plant Industry in Washington has been inves- 

 tigating this disease since 1908. In the spring of 191 1, a bill for the 

 investigation and control of the chestnut tree blight disease in Penn- 

 sylvania was passed and the work began in August, 191 1. The 

 method upon which the commission is working consists briefly in 

 determining the area of blight infection and in removing diseased 

 trees west of a certain line with the purpose of preventing the 

 western spread of the blight. The commission has obtained as ac- 

 curately as possible the amount of infection in the various parts of 

 the State and the results are given in a map on display here. The 

 State is divided into two districts by a line along the western edge of 

 Susquehanna, Wyoming, Columbia, Union, Snyder, Juniata and 

 Franklin Counties, which is approximately the western line of seri- 

 ous blight infection. West of this line a large portion of the State 

 has been scouted and the remainder will be finished early in 191 3. 

 Blight infections have been found in counties adjacent to this line, 

 also in Fayette County, near Connellsville, Warren County, near 

 Warren, and in Elk County, near St. Mary's. These three infec- 

 tions were directly traceable to infected nursery stock and in one 

 case the blight had spread to adjacent trees. A large area of dis- 

 eased chestnut in Somerset County illustrates the harm done by 

 shipping infected nursery stock. The center of this infection is a 

 chestnut orchard, where about 100 scions from an infected eastern 

 orchard were grafted to native sprouts in 1908. Evidently these 

 scions brought the disease into this region for the grafts have all 



