n a report on page 172 of the Thirty-first Annual Meeting
of the Nut Growers' Association held in 1940 cited evidence pro and con
relative to the toxic effect of black walnut on various crops. They
concluded that because of conflicting evidence, the problem of walnut
toxicity was still unsolved and needed further investigation. In 1942,
Babette I. Brown reported on page 97 of the Thirty-third Annual Report
of the Northern Nut Growers' Association, on the injurious influence of
bark of black walnut roots on seedlings of tomato and alfalfa. It was
concluded, from carefully conducted tests, that walnut roots produce a
substance that may be injurious to certain other plants. Experimentation
showed that the walnut root bark produces a substance that is injurious
to alfalfa and tomato seedlings.

During the past years, a number of instances of stunting and wilting of
tomato plants in the vicinity of black walnut trees has been observed.
In 1942, a very definite case of wilting and stunting was noted in
cabbage plants growing in the vicinity of a black walnut tree.

Severely wilted tomato plants were observed on July 30, 1943, in a field
of tomatoes near Egypt, New York. This case was typical of others
observed in tomato fields in recent years. The wilting and stunting were
all located in one corner of the field, on both sides of which large
black walnut trees were growing, and extended out in the field for a
distance somewhat greater than the height of the trees. The rest of the
field planted with the same stock of tomatoes was entirely healthy. The
field had been planted to beans in 1942 and prior to that had been in
grass for at least 7 years. The vascular bundles of affected plants were
browned as in Verticillium or Fusarium wilt and in some bacterial
diseases. No cankers or discolorations were observed on the external
parts of the plants. In order to determine whether or not the wilting
was caused by a fungus or bacterium, plants were collected for
microscopic examination and for culturing to show possible presence of
pathogens. The microscopic examinations showed the absence of fungi or
bacteria in the vascular system or other plant tissues. The browning in
the vascular bundles appeared to be confined to the phloem tissue. All
attempts to culture a pathogenic fungus or bacterium from affected
tissue was negative. Portions of diseased plants with discolored
vascular bundles were placed in a damp chamber and no fungus or