ANTHRACNOSE OF SYCAMORES AND OAKS 
Th anethracnose of sycamores and oaks is a serious disease, especially 
in the northeastern part of the United States where it is frequently epiphy- 
totic. It is. enphytotic on most of the species of the genus Platanus. 
In Europe as well as the United States the sycamores are more commonly 
and destructively attacked than are the oaks. However, in certain regions 
some species of oak suffer severely. 
SYMPTOMS 
The leaves, twigs and small branches are affected. In addition to the 
characteristic lesions produced on these parts of the tree, there are certain 
general symptoms by which a diseased individual may be detected at a 
distance. 
General symptoms. In the photographs provided, oBSERVE:— 
1. The dead, leafless twigs. 
2. The irregularity of the direction taken by smaller branches. 
These twisted and deformed branches are characteristic of this disease. 
3. The excessive twigging on the smaller limbs, producing clumps 
of branches,—witches’-brooms. Note that many of the branches of 
the broom are dead. Make a prawinc of the broom-like growth of the 
branches. 
In the case of trees badly affected, the foliage becomes thin due to the 
falling of many leaves, and those remaining appear scorched owing to the 
large dead areasin them. In the early spring when the leaves are develop- 
ing, all the leaves on a twig may wither and die due to the death of the 
twigs. If this type of injury is general it may be confused with frost- 
injury. 
On the leaves of sycamore. In the material provided, NoTE:— 
4. The large brown areas in the leaves,—the lesions. 
5. That usually the lesion is located on one of the larger veins 
of the leaf. 
The lesions, when first noticeable, are narrow dead areas paralleling 
the veins on both sides. This dead area then rapidly becomes larger as 
the tissues of the vein are killed and the portion of the lamina dependent 
on, the vein for water dies and turns brown. Why do most of the lesions 
extend to the margin of the leaf? 
6. The lesions on the petioles and the pimple-like fruit- 
bodies of the pathogene. 
DRAW sycamore leaves showing these symptoms. 
On the leaves of oak. In the material provided, OBSERVE :— 
7. That in some cases the lesions are similar to those on sycamore 
leaves in that the dead areas are located along the veins; but that more 
commonly numerous small lesions occur without any relation to the posi- 
tion of the veins. How can the difference in size between the lesions 
not located on the veins and those located on the main veins be accounted 
for? Make a prawinc of an oak leaf showing both types of lesions. 
8. On the under surface of the lesions, minute brown spots,—the 
fruiting structures of the pathogene. DRaw as seen with the hand-lens 
or low-power of the microscope. 
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