2I8 
Journal of Agricultural Research 
Vol. XXIV, No. 3 
Tabi,k .-—^Inoculations with spores and mycelium from pure cultures of Botrytis 
cinerea on young trees of Citrus^ and other hosts —Continued 
II. INOCULATED APRIL 17, I913; EXAMINED MAY 20, 1913 
Experi¬ 
ment 
No. 
Host. 
Kind of tissue. 
Results. 
II 
Common lemon... 
Trunk 3 years old. 
Bark soft and decaying over 
areas of 0.5 by 1.5 inches. 
Much gum exuding. 
Bark slightly killed. Slight 
internal gumming. 
No effect on bark. 
12 
Sweet orange. 
13 
Same as above 
without inocu¬ 
lum. 
III. INOCULATED FEBRUARY 6, I915; EXAMINED MAY 18, I915 
14 
Common lemon... 
Branch about 2 years... 
Gumming and fruiting of Botry¬ 
tis on killed bark. 
15 
Rough lemon.... 
Trunk 2 years old. 
No effect. 
16 
Sour orange. 
.do. 
Do. 
17 
Same as above 
without inocu¬ 
lum. 
Do. 
With comparatively young common lemon, peach, and almond trees 
these inoculations with spores placed in cuts resulted in the formation 
of considerable gum. The gum was slight in sweet orange and plum. 
No gum was induced in sour orange, rough lemon, or in any of the control 
cuts except oh peach. The death of the bark was slight and unimportant 
in extent except in the common lemon and peach. 
In general the results of all these experiments showed that the effects 
of Botrytis cinerea were quite different from those of Pythiacystis 
gummosis. This fungus, unlike Pythiacystis citrophthora, was not able to 
make an entrance except through some wound or defect in the bark, and 
it was not able to progress so rapidly in killing the bark through to the 
wood. After a limited portion was killed to the wood, however, a 
larger surrounding area was involved, in which only certain outer layers 
of bark tissue were killed, leaving the cambium alive and capable of 
renewal. There was also in the Botrytis gummosis an outer gummous 
zone beyond the invaded zone, but this was usually less extensive and 
less rapidly formed than in Pythiacystis gummosis. Other conditions 
being equal, there was usually somewhat less gum formation in Botrytis 
gummosis than in Pythiacystis gummosis. 
The fungus was reisolated from the softened invaded area of a large 
number of these lesions. Attempts to isolate the fungus from the outer 
gummous zone failed, just as they did in Pythiacystis gummosis. Only 
rarely was Botrytis isolated from the area where the outer bark was dead 
and hard. Cultures showed that this outer dead cortical layer following 
Botrytis inoculations is, under such conditions as prevail at Santa Paula, 
rapidly occupied by species of Altemaria, Cladosporium, Penicillium, 
Colletotrichum, Fusarium, and other fungi as well as bacteria. 
FACTORS FAVORING BOTRYTIS GUMMOSIS 
Many contributing conditions favor the occurrence and the severity 
of this disease. These are similar to those which favor Pythiacystis 
gummosis, mentioned in Part I of this paper, to be discussed in more 
