A New Garden Enemy and How to Fight It 
A FUNGOUS DISEASE THAT ATTACKS THE PEONY, HITHERTO CONSIDERED IMMUNE- 
HOW ANTS CARRY THE INFECTION—WHAT PREVENTIVE MEASURES MAY BE TAKEN 
BY FI. H. Whetzel 
PROFESSOR OF PLANT PATHOLOGY, CORNELL UNIVERSITY 
Photographs by the Author 
T HE peony is frequently said 
to be a perennial markedly 
free from diseases and pests, but 
our observations extending over a 
period of the last eight years con¬ 
vinces us that this is not entirely 
true. During this time we have 
had the opportunity not only of 
examining many diseased speci¬ 
mens sent to the University for 
diagnosis, but have for the past 
four seasons observed the diseases 
of this plant as they appeared in 
the large collections grown in the 
variety test plats of the University. 
Brought in from many parts of the 
country and in large collections 
from various nurseries, it is not 
surprising that here we had a 
rather complete representation of 
peony diseases, at least five of 
which have appeared in these test plats, for the most part not 
very destructive. One disease, however, has occurred every 
season with more or less severe injury. This we are designating 
as the American botrytis blight of the peony to distinguish it 
from the European botrytis disease which appears to be different. 
It is a disease to be reckoned with in 
growing peonies and the writer has 
been assured by several prominent 
growers that a satisfactory means of 
controlling it would be a distinct boon 
to the growers of this perennial. 
The American botrytis affects all 
parts of the plant above ground, even 
In the peony leaf blight the lesion usually appears first at the 
tip, extending in a V into the blade 
extending down the stem to the 
crown. Whether it ever invades 
the crown and roots is still a ques¬ 
tion. Probably it does not, since 
plants badly affected one season 
appear to grow equally strong tops 
the next. 
The first appearance of the 
disease in the spring is usually in 
the form of a rot at the base of 
young stems. Shortly after they 
appear above ground they begin to 
wilt and droop, finally falling over. 
An examination of the diseased 
stalk shows it rotten at the base, 
the rot usually extending to the 
crown below ground and upward, 
often to the leaves. The advance 
of the disease up the stem is in¬ 
dicated by a water-soaked appear¬ 
ance of the recently affected 
tissues. The rotted part of the stem soon becomes brown or black 
and often covered with a gray-brown felt of the fungus causing 
the disease. Usually only a few stalks in the cluster are affected 
early, though in severe cases all may go down quickly. However, 
stalks in the cluster continue to be affected throughout the season 
if conditions be favorable, and large 
stalks with fully expanded flowers 
often wither and die from a lesion at 
the base. Then, too, stalks affected 
toward the end of the season after the 
tissue is more hardened may not show 
wilting, 
the 
only 
evidence 
of 
the 
(Continued on page 404 ) 
The photograph at the left illustrates a characteristic appearance of your.g peony buds and leaves blasted by the botrytis. In the center are shown 
diseased buds compared to a healthy one, and at the right is a stem exhibiting the water-soaked appearance caused by the fungus 
(373) 
