70 
PARK AND CEMETERY. 
COMPLETE DESTRUCTION OF CHESTNUT TREES BY 
BLIGHT; AS YET NO REMEDY HAS BEEN FOUND. 
TREE CASTING SHREDDED BARK 
AFTER DEATH FROM BLIGHT. 
spring usually remain hanging during the winter, when they 
constitute the only conspicuous symptom of the disease. One 
of the most easily detected and most persistent symptoms is 
the growth of sprouts or “suckers” below the girdling lesions 
of trunk and branches, as well as at the base of the tree. 
The disease is spread by the spores of the fungus which 
are washed down from infected twigs to lower parts by rain, 
which may also carry them through short distances in gen- 
eral. As they are sticky they adhere to dust into which they 
are thus washed down, and this infected dust is carried to 
other trees by wind, but the spores, when free from dust, 
are not apparently disseminated by wind. They appear to 
be spread extensively by birds, especially woodpeckers, by 
squirrels and other rodents and by insects. The disease is 
carried bodily to great distances in tan bark and unbarked 
timber. One of the most prolific sources of infection has 
been the transportation of diseased nursery stock. 
The spores may develop in any moist hole in the bark. 
The hole may be a cut or wound, but by far the most com- 
mon place of infection is a tunnel made by one of the in- 
sects known as borers, for these tunnels are moist even in 
dry weather. The development takes place in the inner 
bark and cambium layers, and the fruiting pustules are sub- 
sequently extended through the outer bark. 
No method of producing immunity to the disease in indi- 
vidual trees or of curing them when attacked has yet been 
discovered. The most effective individual treatment, how- 
ever, would be of little value in the present situation, for it 
would not be practicable to apply such treatment to forest 
trees. 
A method of controlling the disease which seems more 
practical and which has been tested with considerable suc- 
cess is outlined in Bulletin 467 of the U. S. Department of 
Agriculture. The investigations made by the department 
soon showed that the disease does not advance rapidly in a 
solid line but spreads from isolated centers, often many miles 
in advance of the main line of infection. It seemed probable 
that these centers of infection, if detected at an early stage, 
BARK OF YOUNG CHESTNUT TREE SHOWING 
CANKER COVERED WITH WART-LIKE 
PUSTULES, WHICH BEAR THE MINUTE 
SPORES OF THE BLIGHT. 
PUSTULES ARE HERE SHOWN PRODUCING 
GELATINOUS THREADS, BEARING 
SUMMER SPORES OF THE 
BLIGHT (ENLARGED). 
