SPECIAL PART II 
DISEASES OF OHIO PLANTS. ARRANGED ALPHABETICALLY 
ACCORDING TO HOST PLANT 
ALDER 
Powdery Mildews. The alder suffers from several powdery mildew fungi on 
the leaves (Phyllactinia suffulta Sacc., Erysiphe aggregata, (Pk.) Farl., 
Microsphaera aini (DC) Wint.) These retard development as with other leaf 
coverings. Alder may also suffer from two or three leaf infecting diseases such 
as an anthracnose and a leaf-spot. We have as yet little data concerning other 
occurrences owing to the neglect of the study. 
Stem Biights. From England an interesting branch parasite (Ditopella 
fusispora De Not) has been reported by Plowright. This may or may not as 
yet occur with us. 
Root Tubercles. These root developments on the alder and some other woody 
plants are commonly described as Mycorhiza, The particular organism ( Frankia 
alni Nor.) has attracted a good deal of attention from students of forest problems 
in Europe. Investigations of such growths upon the roots of our woody plants is 
very much needed at this time in Ohio. 
ALFALFA--LUCERN ~ 
Anthracnose. Twonew anthracnoses have been discovered attacking alfalfa; 
the first of these, Colletotrichum trifolii B&E, so far as we know occurring 
exclusively on plants of this family, the other, Colletotrichum sp., occurring only on 
alfalfa in northern Ohio. The first one, which we may call clover anthracnose, 
was discovered in Tennessee and has appeared upon alfalfa as well as red 
lover in the southern portion of Ohio. It is less prevalent on alfalfa than upon 
the red clover. Up to this time this disease has not been discovered upon either 
host in the northern half of the state. The second anthracnose occurred recently 
upon alfalfa from Sandusky and Carroll counties and has not been described. 
Both of these diseaseses Show as a specific lesion or diseased spot on the stem or 
leaf-stalk in the advanced stages of attack. Following this the plants wilt or 
die and are discovered in this way. The disease is tuo new with us to measure 
its injuries directly. To the writer it appears less serious than the dodders or 
the root-rot troubles. 
Bacterial Blight.(Yellowing). A bacterial blight of alfalfa, of which the 
causal organism has not been definitely determined, has been reported from 
Colorado where it appears to be spreading. In 1907 and to a still greater extent 
in 1908, there was much complaint of general yellowing of leaves of second crop 
alfalfa in Ohio and adjoining states, even extending to North Carolina. The 
symptoms were general yellowing of this crop. With brighter, drier weather 
later the next succeeding crop was of normal color. Bacteria have been found 
by the Assistant Botanist in connection with this trouble in specimens from 
eight localities and from four different counties in Ohio during 1908 and 1909. 
Downy Mildew. The downy mildew fungus (/eronospora trifoliorum D’By) 
has occurred in Colorado, and is very liable to occur in our state. No sugges- 
tions can yet be made as to its prevention 
Leaf-Spot Fungus. This forage plant is grown in parts of Ohio. It is attacked 
by the leaf-spot fungus ( Pseudopezia medicaginis ( Lib.) Sacc.) which is found upon 
both leaves and stem. Thesmall dark spots produced by it are easily seen. In 
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