ly during that time. In 1935 scions and buds were taken
from diseased eastern black walnut and butternut trees growing at
Arlington Farm and grafted or budded on eastern black walnut stock
growing in the original nut tree nursery at the Plant Industry Station
at Beltsville, Maryland. This was done in an attempt to determine
whether the disease was caused by a mineral deficiency or by a virus.
All buds and scions died, but the following year two of the seedling
rootstocks showed characteristic symptoms of the bunch disease. Since
this disease was already present on the station farm it was not
definitely known that it was transmitted to the stocks by budding or
grafting the diseased material on them.

In December of 1946 Hutchins and Wester[16] presented a paper before the
American Phytopathology Society giving the results of their studies on
the bunch disease. In this paper they reported that the disease was
transmitted by patch bark grafts performed in 1944 and 1945 and that the
incubation period varied from several months to two years. It was
concluded that since the disease was transmitted by grafting, and in the
absence of a visible pathogen, a virus causal agent was indicated.

Symptoms

The characteristic symptoms of the bunch disease are mainly the
production of brooms or sucker shoot growth on the tree trunk and main
branches and the tufting of terminals, profusion of small branches from
axillary buds, the dwarfing and narrowing of the leaflets, and the dying
back of the trees resulting sometimes in the death of the trees. The
principal symptom is the production during summer of bushy, wiry growth
caused by the breaking into growth of lateral buds that normally would
remain dormant over the winter. These buds produce shoots that again
branch from lateral buds and the process may be repeated for three or
four times, resulting in a tightly packed mass or bunch of small, wiry
twigs and undersized leaves. Another characteristic symptom is that this
growth proliferation continues unabated until the first frost, and,
since the wood of these shoots is thus not properly matured, killing
back of the diseased portions of the tree usually occurs with the first
hard freezes of winter.

As the disease progresses, the wood in the main branches becomes very
brittle and is easily broken by wind or ice. This condition is followed
by the dying back of branches and finally the death of the tree. Trees
even moderately affected