SCLEROTINIA ROT 
This is a very common disease of a great variety of plants. It is especi- 
ally destructive in rainy seasons or in very moist situations. Due to the 
different symptoms exhibited in a great variety of hosts it has come to 
be known under several names as; stem-rot in seedlings, soft rot in stored 
roots and bulbs, and ‘“‘drop’’ in lettuce. 
SYMPTOMS 
The most usual point of injury is the base of the stem, but the leaves 
of such plants as cabbage and lettuce, especially when packed together 
in heads are commonly affected. Fleshy roots, when stored together often 
suffer from this disease. Pods, fruits and twigs sometimes show lesions. 
On the stems. The name stem-rot is applied to the disease in those 
cases where the lesions are chiefly at the base of the stem. The symptoms 
are in general the same on the different hosts. Examine the diseased 
stems provided. OBSERVE :— ; 
1. A bleaching of the normal color of the tissues accompanied 
by a softening and sometimes a water-soaked appearance. If fresh 
material is available, examine for these characters. 
2. The appearance, in a short time if the air is moist, of a densely 
matted pure white felt of mycelium on the surface of the lesion. Examine 
diseased specimens which have been kept for a time in a moist-chamber. 
3. The large black bodies,—sclerotia, on the surface of the lesion 
or more frequently within the pith of the stem. These sclerotia are at 
first soft cream-colored bodies embedded in the white myceliai felt or in the 
pith. They soon turn black and become firm and tuber-like. 
Make sKETCHES to show these distinguishing symptoms. 
On the heads of lettuce. ‘‘Drop” is frequently a serious disease of 
lettuce. Examine the diseased plants provided and oBSERVE:— 
4. The collapsed and wilting state of the plant. It has ‘‘drop- 
ped.” SKETCH a diseased and healthy plant. 
5. The point of injury; extent of the lesion. 
6. The soft slimy condition of the affected tissues. Note also 
odor, color, and consistency of the affected parts. How does this rot 
compare with the bacterial soft rot? 
7. The loose white felty masses of mycelium, on and between the 
decomposed leaves. Larger masses of very compact aggregations of 
mycelium which are the beginnings of sclerotia. 
8. In somewhat older material the mature sclerotia which have 
become very hard with black, tough outer walls. 
_ On fleshy roots. As a storage-rot of carrots and turnips, this disease 
is often exceedingly destructive. Examine the diseased roots provided. 
OBSERVE :— 
= 9. The white felty mat of mycelium covering the surface of the 
esion. 
_ 10. The hard tuber-like sclerotia; some mature black and hard, 
others just forming as white cottony masses on the mycelial felt. 
11. The soft decay of the tissues beneath the mycelial felt; 
odor, color, taste. : 
36 
