MAPLE DISEASES 



231 



Wilt 

 Caused by Vertieillium sp. 



Wilt is a recently discovered and little known disease of 

 silver, Norway and sugar maples. It has been found in New 

 York, Virginia and Ontario, Canada, and is probably more 

 widely distributed. Several trees have been observed which 

 were dying or had been killed by this disease. It seems 

 probable that a part of the common sun-scorch of maples 

 may be found to be another symptom of this disease. 



Si/mptoms. 



In the few observations made on this disease, the common 

 and only external symptom is the blanching and sudden wilt- 

 ing of the foliage in midsum- 

 mer. The leaves of an entire 

 branch or side of the tree wilt 

 and become dry and ■«Tinkled 

 at the same time. On cut- 

 ting into the sapwood of the 

 affected branch or trunk, the 

 outer layers will be found more 

 or less streaked with greenish 

 colored longitudinal lines. No 

 external fruiting-bodies have 

 been found on the bark. The green discoloration extends up- 

 ward and downward in the branches and trunk and may 

 enter the roots (Fig. 42). 



Cause. 



The wilt of maples is due to an unnamed fungus of the genus 

 Vertieillium. Closely related species cause a similar disease, 

 usually confined to the roots, in barberry, eggplant and numer- 

 ous other plants. Other species of the same genus cause wilts 



Fig. 42. — Sections through the trunk 

 of a small maple affected by wilt. 



