2 Department Circular 370, U. S. Dept. of Agriculture 
tinuation of this cooperation is necessary in order to secure needed 
information with the limited funds available for inspection. Fore- 
casts on the future spread of the blight also are given. 
SYMPTOMS OF THE DISEASE . 
In stands recently attacked the first evidences of the disease are 
‘ generally to be found on the smaller branches and at the bases of 
‘young sprouts from stumps. When such branches and sprouts are 
killed by the blight during the growing season the dead leaves and 
burs adhere tenaciously, forming characteristic “flags,” which are 
very helpful in locating infections from a distance. These show up 
in summer in striking contrast with the healthy green leaves and in 
winter with the defoliated remaining portions of the trees. Close 
examination will determine whether these flags are due to the disease 
or to mechanical injuries. If the symptoms are caused by the 
blight, prominent lesions on the branch, trunk, or even exposed roots 
indicate the growth of the parasite within the bark. These areas 
of diseased bark vary in size, color, elevation, and the fruiting struc- 
tures produced. 
The cankers are generally elliptical in outline at first. Because the 
growth of the fungus is slightly more rapid. up and down the 
stem, the longer dimension of the lesion lies in that direction. When 
the two edges of the lesion meet around the stem (Pl. I) the result- 
ing ring of diseased tissue cuts off the flow of sap. The foliage 
above such a girdle wilts, turns yellow, and dies. Usually it does 
not fall, but remains persistent for a considerable period. There is 
wer iy) a development of sprouts or suckers below the girdle 
Pl. If). 
The cankered areas may be either sunken below or swollen above 
the surrounding bark, or they may be combinations of the two. On 
smooth bark the lesions are sharply demarked, sometimes even ap- 
pearing as though outlined with black pencil lines. The margin may 
be raised or slightly water-soaked when the fungus is advancing 
rapidly. It is usually regular, but in some cases it is so irregular 
as to resemble amceboid flow, as shown to a slight extent in Plate I. 
At times the reddish orange color of young cankers stands out in 
striking contrast with the green bark, but both normal and diseased 
barks darken with age, and the coloration of the canker becomes 
less conspicuous when it.assumes its usual red-brown to sepia tones. 
With increasing age cankers generally become rough, split, and 
cracked, with peeling bark (Pls. III and IV). The sunken cankers, 
which are generally smooth barked at the center, often develop 
roughened raised margins. Mature portions of cankers are dotted 
-with fruiting structures, which most commonly resemble orange or 
red-brown pinheads. These fruiting bodies are more conspicuous 
on smooth lesions, but are also evident in the cracks of rough 
cankers. 
Many cankers show the points at which the fungus organism 
entered the bark. Wormholes, cicada stings, and mechanical in- 
juries are favorite points of attack. Diseased twigs frequently 
carry infection into larger parts. Sprouts are commonly infected 
where spores and moisture collect at their bases, 
