Jan. 6,1923 
A Phytophthora Footrol of Rhubarb. 
3 
from Ithaca, N. Y., where it was isolated from rhubarb in two separate 
gardens. It is evident, therefore, that the data here given on distribu¬ 
tion may have to do with the disease caused by either one of the organisms, 
except in those cases in which the specific organism is clearly noted. It 
is hoped that it will be possible, after another season’s observations, to 
distinguish between the diseases under field conditions. Mr. Beach has 
much additional data in this connection which will probably be pub¬ 
lished soon in a bulletin of the Pennsylvania Agricultural Experiment 
Station. 4 His paper is an important and valuable contribution to this 
and other phases of the rhubarb crownrot problems. 
It is not possible to make any estimate of total loss at this time. Since 
rhubarb is rather extensively grown on a commercial scale and the dis¬ 
ease is widespread, it will have to suffice to say that the f00trot is of con¬ 
siderable economic importance. 
DESCRIPTION OF THE DISEASE 
The first outward manifestation of Phytophthora footrot is a sudden 
wilting of the foliage, usually of one or two leaves only. The base of 
the petiole, or leaf stalk, is the point affected. Here a distinct lesion is 
found, slightly sunken, sometimes not colored, and sometimes in sharp 
contrast with the pink or light green of the normal petiole because of 
its brown color. A leaf that has reached the wilting stage is shown in 
Plate 1, A. The lesion has practically girdled the base of the stem. 
This area advances rapidly, and in less than 24 hours the stem may col¬ 
lapse at this point, allowing the leaf to fall to the ground. Leaf stalks 
with the disease slightly farther advanced are to be seen in Plate 2. The 
tissue is killed so quickly that secondary organisms, particularly bac¬ 
teria, gain entrance almost immediately. These contribute to the rapid 
decomposition of the fallen leaf, turning it quickly into a putrid mass, 
especially at the base, as shown in Plate 2. This factor makes it diffi¬ 
cult to isolate the causal organism. Fungi as well as bacteria play a 
leading part in the further destruction of the leaf. A species of Colleto- 
trichum, probably the same one treated by Stevens ( 24) and considered 
by him to be Colletotrichum erumpens Sacc., is found in great abundance 
at times on decumbent rhubarb leaves and petioles in early and late 
stages of decomposition. Plate 3, B, illustrates a leaf petiole recently 
fallen with Colleto trichum appearing along its entire length. Plate 3, A, 
shows a leaf entirely covered with this fungus in a fruiting condition. 
In weather favorable to the disease the first symptoms are followed 
in a day or two by the infection and collapse of other leaf stalks in the 
plant, as shown in Plate 4, A. Finally, all the leaves drop, leaving the 
plant entirely dead (PI. 4, B). Meanwhile other plants in the field are 
similarly affected and many of them are killed, so that the field may show 
large vacant areas. 
A study of many plants in different stages of infection showed that the 
fungus advances into the root from affected leaf stalks, causing a brown 
decay. Thence it spreads rapidly through the upper portion of the 
root, killing the other leaves and leaf buds. Plate 5, A, a section through 
a recently killed plant, shows the advancing edge of decay due to the 
causal organism. At the points marked (X) the fungus was found and 
identified as Phytophthora. Plate 5, B, shows clearly how the fungus, 
4 This bulletin has since appeared: Beach, W. S. the CROWN ROT oE rhubarb caused by phy¬ 
tophthora cactorum. Pa. Agr. Exp. Sta. Bui. 174 , 28 p., 25 fig. 1922 . Bibliography, p. 27 - 28 . 
