United States, but it has not, probably because the vectors are not efficient 
transmitters of the disease. It has, however, caused considerable damage in many 
oak woodlots and forest stands in Wisconsin, Minnesota, West Virginia, and lowa 
(438). Control measures include sanitation by removal of infected trees and trench- 
ing between infected and healthy trees to eliminate root grafts. 
Persimmon wilt is a fast-killing disease of common persimmon that occurs in 
the Southeastern States west to Texas and Oklahoma. It is caused by the fungus, 
Cephalosporium diospyri Crandall, which produces masses of spores beneath the 
bark of infected trees. In smooth-barked trees the spores occur in such large masses 
that the overlying bark is raised in the form of blisters. When these blisters break, 
the spores are released and then blown away by the wind. In rough-barked trees the 
spores are produced in the cambial region and are released when the bark begins to 
disintegrate or is removed or broken off. 
Wind is undoubtedly the major agent of spore dissemination, but some spread is 
also probably effected by insects such as the bostrichid, Xylobiops basilaris (Say). 
The adults of this species, some of which attack healthy trees, become contami- 
nated when they emerge through spore masses on dying trees. Feeding injuries on 
the terminals and twigs by adults of this twig girdler also serve as entry courts for 
windborne spores (263). 
Fungi that cause blue stains are introduced into pines by bark beetles, and the 
fungi kill trees (65, 9/8). Blue stain occurs in felled timber, in beetle-infested trees, 
and in trees weakened by fire, drought, or other adverse factors. 
F-519913 
Figure 6.—Oak tree killed by the oak wilt 
fungus, Ceratocystis fagacearum. 
23 
