July 15, 1924 
Botrytis Rot of the Globe Artichoke 
89 
was saturated and water was condensed 
on the buds at least once a day. 
In inoculation tests with spore sus¬ 
pensions made with wounded and un¬ 
wounded buds at temperatures ranging 
from —1° C. to 26°, negative results 
were obtained at — l o ,0°,0.5°, and 1.5°. 
Infection resulted occasionally at 5.5°, 
but only in wounds. The number of 
infections obtained was greater at 7° 
than at 5.5°, and still greater at 10°, 
with a maximum between 15° and 21°. 
Between 26° and 32° infection was 
obtained only occasionally. All in¬ 
fection obtained started in artificial 
or natural wounds (PI. 1 D). Scales 
which had been wounded and dipped in 
spore suspensions developed lesions of 
2 to 5 sq. cm. with sporulating mycelium 
on the surface in nine days at 26°. 
The presence or absence of wounds 
seems, therefore, the most important 
limiting factor so far as infection by 
spores is concerned, with moisture, and 
then temperature next in importance. 
For infection by mycelium, however, 
moisture is the main limiting factor, 
temperature and wounds ranking in the 
order named. 
Infection with spores was not ob¬ 
tainable when the tissues were not 
wounded. Wounds are abundant and 
inevitable, however, on both the grow¬ 
ing and the harvested buds. There is 
more or less tearing of the scale tips 
during growth, for they are curved in¬ 
ward and indented (PI. 1, A, D) so that 
tensions arise at the spine and lead to 
tearing as the scales enlarge. A large 
wound is made when the bud is cut from 
the plant in harvesting (PI. 1, B), and 
later when buds are crowded into crates 
for a tight pack there is more tearing of 
the scales and considerable bruising of 
the sides as well. 
Holding tests made at 7° C. show that 
the buds of a lot which appear sound at 
the beginning of a test develop Botrytis 
decay progressively, and eventually 
almost all show decay. Possibly this 
is due to a weakening of the tissues. 
It is a general observation in the field 
that Botrytis readily attacks aging or 
weakened parts of plants, such as the 
outer dying leaves of lettuce or celery. 
Field observations indicate that the 
age or vigor of artichoke buds is a factor, 
inasmuch as the small buds produced 
at the close of the seasonal productive 
period or by old plants show greater 
decay than buds from more vigorous 
plants, some inspection certificates re¬ 
porting 4 to 10 per cent decay in large 
buds and 20 to 30 per cent in small ones. 
It has also been observed that tissues 
killed or weakened by overheating or 
freezing are more readily attacked than 
healthy ones. 
99179—25t-3 
THE DISEASE 
PLACE OF ORIGIN, SPREAD, AND DEVEL¬ 
OPMENT 
Observations in packing houses indi¬ 
cate that even though some buds with 
small lesions are packed, by far the 
greatest number of boxes contain few 
buds showing any signs of lesions or of 
the fungus. Field observations indi¬ 
cate that spore contamination in the 
field is probably the original and chief 
source of the disease in transit. Here can 
be found buds and other parts of the 
plants covered with sporulating my¬ 
celium. A much more serious source of 
infection, however, is the immense 
amount of plant trash allowed to lie in 
or adjacent to the fields, which is often 
covered with an extensive sporulating 
growth of Botrytis that liberates clouds 
of spores whenever disturbed. The 
great quantities of plant trash exist be¬ 
cause the bearing plants, which resemble 
huge thistles, are cut down annually in 
May and their roots allowed to sprout or 
sucker. The new tops come into bear¬ 
ing during September and October, and 
in the fourth or fifth year, when buds 
begin to be small and hard, the plants 
are replaced by new shoots. 
Examination upon arrival of buds 
taken out of boxes not previously 
opened shows that the lesions usually 
start at the tips of the scales or at the 
cut stem surface. This indicates that 
the original infections come from spores 
that lodge in these places and that sec¬ 
ondary infections in transit are pri¬ 
marily by contact. Secondary infec¬ 
tion by spores also may take place, 
since infected scales frequently are cov¬ 
ered with sporulating mycelium. 
That the bud surfaces carry either 
spores or mycelium of Botrytis is easily 
demonstrated by taking buds from 
packing boxes and exposing them to 
favorable temperature and moisture 
conditions. Botrytis rot develops 
almost invariably. In fact, if the buds 
were not washed and sterilized, it 
seemed impossible to have control ma¬ 
terial come through the experiments, 
which lasted from several days to sev¬ 
eral weeks, without developing Botrytis 
rot. That the contaminations were 
mostly on the surface is proved by the 
fact that a few minutes’ dipping in cor¬ 
rosive sublimate solution sufficed for 
sterilization. Thorough washing was 
also frequently sufficient. Yet occa¬ 
sional development of decay in buds so 
treated proved that incipient but in¬ 
visible infections were also present. 
It was found that spores or incipient 
infections may lie dormant for consider¬ 
able periods if conditions are unfavor- 
