DISEASES OF CULTIVATED PLANTS 429 
PINE 
Damping-Off. A damping-off fungus (Fusarium sp.) has recently been very 
troublesome with seedlings of white pine in theeast. This has been investigated 
and remedies have been tried successfully. These are either dilute sulfuric acid 
or powdered copper sulfate and lime; the former being sprayed on the seedlings 
about the base and the latter applied as dust. (See Cir. 4, Bur. Plant Indus.). 
It is likely that with efforts to grow white pine for timber purposes in this state, 
troubles of this type will not be restricted to this parasite. 
Leaf Blight and Leaf-Spot. Leaf troubles have been met in most areas where 
white pine grows naturally or is being cultivated very largely. One of these 
so-called leaf blights is referred to a fungus, (Septoria parasitica Hartig). 
It has been found in adjoining states if not in Ohio. Another leaf-spot fungus 
(Phoma strobi Berk and Br.) is quite prevalent upon white pine in Europe. It is 
believed that this parasite or a closely related one, (Phoma strobilinum P. C.) 
occurs within our borders. Remedies have yet to be worked out for these troubles. 
Root-Rots are to be expected in addition to the damping-off fungus before 
mentioned, especially among seedling pines under culture. 
Rust. In Europethe blister rustfungus (Cronartium ribicolum Dietr. FPeri- 
dermium strobi Kleb.) has been long known as a serious drawback to the culture 
ofthe white pine. Curiously enough this rust has until recently not been known 
inthe United States. Not long since warning was sent out by the Department of 
Agriculture that this rust had appeared in America and should be sought for 
upon its alternate hosts, the white pine (Aecidia) and the currant and gooseberry. 
(Uredo- and Teleutospores). Upon the pine the aecidial stage develops numerous 
orange cluster cups infecting the stem toward the base. This causes high mor- 
tality among the young pines. Upon the currant and gooseberry the uredospores 
show yellow color which darkens as the teleutospores form. These are to be 
sought in August or early September, and by reason of the importance of this 
rust merit early attention by students of these diseases. 
PLUM ° 
Black-Knot. This is the same disease as that described under black-knot of 
cherry. It is more frequent upon the Damson than upon the other European 
plums, but requires only the removal and burning of the knots each year before 
March, in order to grow plums successfully and without serious injury from this 
disease. 
Brown-Rot is by all odds the most 
serious disease with which Ohio plum 
growers have to deal, outranking by 
far black-knot, shot-hole fungus and all 
the other ills plums are heir to. It is 
the same in character as the rot of other 
stone fruits. As with the peach, the 
rot fungus (Sclorotinia (Monilia) fruc- 
tigena (Pers.) lives over winter in the 
mummy rotted plums of the year before 
and possibly, to a limited extent, in 
affected branches. The first step in 
successful control of rot is the removal 
and burning of these old plums. The 
next step is to spray thoroughly, before 
Fig. 79. Cluster of plums destroyed by rot the buds open, and to continue the 
causing “‘mummies. Mummy” plums are : iepren 
dangerous whether left upon the tree or dropped spraying and picking the rotted plums 
to the ground, since they carry the rot fungus 4s circumstances demand. Likewise, 
over the winter period. 
