South Bend news-times. (South Bend, Ind.) 1913-1938, 1922-10-14
Scientists Discover Infectious
Plant Maladies Are Ere
quently Transmitted.

Isl with plant disease also has now
been discovered by two investigators
In Purdue university Lafayette In
diana, who find that a battling dis
ease of the tomato plant Is carried
over the winter and given TO the new
plants In the following summer by
two hardy weeds grounj-cherry and
horse-nettle. The story of how they
ascertained this and the resulting al
vice to gardeners are given i'm the
Country Gentleman by Albert a.
Hansen who entities his article
The Typhoid Marys Of the Plant
World" Writes Mr.. Hansen:
A few years ago the world was
startled by the discovery that GER
tain persons are carriers Of human
diseases. A case cited of a waitress
in a restaurant who unconsciously
distributed typhoid right and left
among patrons she served. She soon
received the name of Typhoid Mary.
Two Typhoid Marys have recent
" been discovered in the plant
world, and the discovery means
much to all who grow tomatoes,
whether in gardens, i'm fields or in
greenhouses, particularly growers OF
canning tomatoes.
The detective who made the dis
covery are two workers in the botani
cal laboratories of the Purdue Uni
versity Agricultural Experiment Sta
tion-Dr. NJ w Gardner and James
b. Kendrick. Whereas the human
carriers harbor typhoid. the plant
carriers harbor tomato mosaic. a
serious disease that annually causes
hundreds OF thousands of dollars
loss tomato growers and is frequent
~ the limiting factor i'm profitable
tomato culture. Tomato MOSAIC IS
one of the most battling plant dis
eases known 10 science. The real
cause Of the disease is unknown,
since II has been impossible TO isolate
either bacteria or fungi that might
be responsible for the trouble
The commonly accepted theory
is that the mosaic is due TO a virus
similar in nature 10 the virus which
is supposed to caBse rabies. infan lie
paralysis and measles in the human
family.
once a field IS infected with mo-
said the disease appears year after
year in what was hitherto a myster-
ious manner. Repeated tests showed
that neither the soil nor the toma-
10 seeds carried the Infection.
Whence. then, did il Gomez Il was
known that certain insects. notably
plant lice were capable of spread
ing the virus from one plant 70 an
other. but was the disease carried
over the winter?
Gardner and Kendrick started a
systematic search for the perennial
source Of infection. They knew that
there were human carriers of dis
ease. so they reasoned that the in
lection might be carried by wild
plants Of the perennial type and
transferred from these hitherto un-
suspected sources to the tomatoes by
means Of insects.
working on this theory. the
plant Culprits were finally located 1t
was noted that two common weeds.
ground-cherry and horsenettle fire.
quently exhibited signs Of mosaic
when growing near diseased toula-
toes It was also noted that neither
OF these two species was diseased
when found growing wild i'm sections
where tomatoes were not cultivated.
Another link i'm the chain Of evil
dence was the fact that both OF
these weeds grow from deep-rUn-
ming roots that live from year 20
year. sending up new shoots each
spring And both the ground-cherry
and the horse-nettIe are closely re-
lated botanically 10 the common to-
matO.
why couldn't the running roots
produce diseased shoots year after
year. acting as perennial sources OF
Infection And why couldn't plant
lice, flea beetles and other common
insects that attack both the weeds
and tomatoes carry the MOSAIC read
ly from the diseased shoots Of
ground-cheTry and hOrse-uettle %
the young growing tomatoes in the
plant beds or In the delds2
THAI was the theory the workers
attempted 20 prove First they in
oculated healthy tomato plants with
the juices of diseased ground-che cry
and horse nettle. The mosaic was
readily Transmitted 20 the tomatoes
by this means.
Then. insects that had fed upon
diseased groUnd-cherry and horse
nettle were inclosed in an insect
proof cage and allowed 20 feed upon
healthy tomato plants. The disease
soon became evident on the once
-I~ir-frr fnr0a-oau
Again. healthy tomato plants
were sent out in fields badly infest-
ed with mosaic and protected by in
sect PROOF cage. and the plants ma
tured free Of mosaic. Diseased
ground-cherry and horse -net.le
plants were closely watched for sew
eraI years. and the mosaic was not
cd each spring IN the young shoots.
Other experiment OF a more tech
meal nature were performed. and
it was proved thai both ground
cherry and horse-nettlc carry tOUa-
20 mosaic year after year and the
disease Is transmitted from these
sources to the tomato crop b. means
Of insects. particularly plant lice.
What does all this mean 20 the to-
mato grower asks Mr.. Hansen. u
means that one OF the most ruinous
OF all tomato diseases and be con-
troIIed by destroying the ground
-r.sFn Ia "a