Apr. 21, 1923 
Gummosis of Citrus 
209 
around the branch for a distance of 8 cm. below the wound, and a large 
quantity of gum had formed. The control cuts on all three varieties 
healed perfectly without gumming or evident injury to the trees. 
On July 2, 1913, inoculations were made at Whittier, with Pythiacystis 
citrophthora in cuts on the bark of sour-orange, sweet-orange, and a number 
of young deciduous fruit trees. The results on September 26, 1913, are 
given in Table IX. 
TabIvE 1^,—Comparative inoculations with Pythiacystis citrophthora into Citrus and 
deciduous fruit trees. Inoculations made July 2, IQIS; observations, September 26, 
1913 
Inocu¬ 
lation 
No. 
Host. 
Results. 
I 
Sour-orange stock (Valencia orange 
scion above). 
Slight gumming, but healing rapidly. 
2 
Sour-orange stock (Valencia above)... 
Healed perfectly, no gumming. 
3 
Sour-orange stock (lemon above). 
Healed with swollen scar only. 
4 
Valencia orange scion, hardened tis¬ 
sue (sour-orange stock below). 
Gumming copiously with killing of 
small amount of tissue. 
5 
Valencia orange, same tree as No. 4, 
younger tissue. 
Gumming copiously; 15-cm. strip of 
bark on one side of twig killed. 
All healed perfectly without visible 
gumming on surface. 
6 
Control cuts on sour-orange and on 
Valencia orange bark (not inocu¬ 
lated). 
7 
Almond (2 trees). 
Gum exuded. Tissue slightly killed 
beyond cut. 
8 
Almond ('control, not inoculated). 
Healed perfectly without gumming. 
9 
Peach (i2-mm. stem). 
Much exuded gum. Bark killed 5 by 
1.3 cm.; killed wood 8 cm. long. 
Healed perfectly with slight gumming 
10 
Peach (control, not inoculated). 
II 
Embank plum. 
Gumming, outer part of bark killed 
and sunken, but healing imder- 
neath. 
12 
Burbank plum (control not inocu¬ 
lated). 
Healed perfectly, no gum. 
13 
Pear. 
Healed with enlarged scar. 
14 
Pear (control). 
Healed with slight scar. 
As before, the sour-orange bark showed high resistance while the sweet- 
orange (Valencia) bark was considerably affected by the fungus. Of the 
deciduous fruits tested, peach was most affected, almond and plum 
slightly, and pear scarcely at all. 
In Table X are shown the results of inoculation into branches of 
various species by placing bits of Pythiacystis-infected fruit into cuts. 
Table X.— Comparative inoculations on Citrus branches, October Q, 1914; observations 
October 22, IQ14 
Experi 
merit 
No. 
Host. 
Size of diseased lesions. 
Gum.^ 
I 
Common lemon. 
Cm. 
5 by 1.3 
3 
2 
Ho . 
5 by I. 3 
2. s by 0. 5 
3 
3 
Citron. 
3 
A 
Ho . 
2. s by 0.3 
4 by I. 0 
3 
5 
Sweet orange (Valencia)... 
3 
6 
Sweet orange (navel). 
3 by I. 0 
3 
7 
Sour orange. 
I. 2 by 0. 5 
2 
8 
Controls. 
0 
0 
1 o=none; i= slight; 2= medium: 3= copious. 
