orty-Second Annual
Meeting of the N.N.G.A. at the University of Illinois. The following
report is aimed at bringing up to date the present known distribution
of the oak wilt disease, recent developments in scientific research on
the disease, and possible control measures.

The oak wilt disease is caused by the fungus _Chalara quercina_ Henry
and is characterized by a very noticeable bronzing and wilting of leaves
that drop prematurely. Brown streaks are usually present in the outer
sapwood. These symptoms may be seen from June to September or until
normal autumn colors of the foliage develop.

More than 30 species of oak are known to be susceptible to the disease.
Other susceptible genera of the family Fagaceae are Chinese chestnut,
_Castanea mollissima_, golden chinquapin, _Castanopsis chrysophylla_,
tanbark oak, _Lithocarpus densifiora_, and _Nothofagus_ from South
America. The red and black oaks seem to be most susceptible and are
often killed within 6 weeks after infection.

Distribution

During the past few years the oak wilt disease has spread with such
rapidity and destructiveness among valuable forest and shade oaks in
parts of the eastern half of the United States that its seriousness is
now well recognized. At present oak wilt is known to be in the following
states: Wisconsin, Iowa, Minnesota, Illinois, Missouri, Indiana,
northern Arkansas, eastern Kansas, southeastern Nebraska, Ohio,
Pennsylvania, West Virginia, northwestern Virginia, western part of
North Carolina, eastern Tennessee, northeastern Kentucky, western
Maryland and southern Michigan. Aerial surveys for 1952 are not yet
complete, but there are indications of extensive new infections in
Pennsylvania, Ohio, and West Virginia while the other states show a
moderate increase in the number of infections.

The first case of oak wilt in Illinois was seen in Rockford in 1942.
Today 54 of the 102 counties in the state have oak wilt areas. The
disease is present in both the extreme northern part and the
southern-most tip of the state. Practically all wilt areas in the
southern half of Illinois consist of 5 trees or less that appear to have
died within the last 4 years, indicating a recent spread of the disease
southward. A similar condition exists in southern Missouri and northern
Arkansas.

Developments in Research

In 1942 a report from the Wisconsin Agricultural Experiment Station
revealed that the oak wilt disease was caused by a fungus, and