THE CHESTNUT BARK DISEASE. 



THE DISEASE AND ITS METHOD OF ATTACK. 



The State Forester wishes to call the attention of the citizens 

 of the Commonwealth to a serious disease of the common chest- 

 nut (Castanea dentata), a disease which has been working 

 for some time in the States of New York, New Jersey, Con- 

 necticut and Pennsylvania, and which has been found to be 

 slowly gaining a foothold in Massachusetts. This disease is 

 caused by a fungus known botanically as Diaporthe parasitica 

 (also as Valsonectria parasitica), and grows in and derives nour- 

 ishment from the tissues of the inner bark of the chestnut tree. 

 The fungus is conveyed from one place to another by means of 

 " spores " or fruiting bodies, which are analogous to seeds in the 

 higher orders of plants. These spores, being small and very light,, 

 are easily carried long distances by the wind, and when blown 

 against a chestnut tree find lodgment in any wounds, of which 

 even the healthiest tree often has a great many, that may be in 

 the bark. It makes no difference with the disease whether the 

 spores find a refuge in the tissues of the thick bark of the trunk 

 or the thinner bark of the small twigs, the fungus develops 

 equally well. It is true that in localities where the disease is 

 rare the spread is slow, but the fact that it can increase to an 

 alarming rate has been proved in our sister States, where it is 

 no exaggeration to say that in certain sections the chestnut is 

 becoming extinct. 



GROWTH. 



The spores having gained an entrance, the fungus begins to 

 spread by sending out many small fibers, much in the same way 

 that a plant sends out roots. These fibers, pushing about and 

 through the growing cells of the tree to obtain nourishment, form 

 a close network which soon saps the life of the section where 

 they are. 



