430 OHIO EXPERIMENT STATION: BULLETIN 214 
controlthecurculio. For details of treatment see calendar. No halfway meage 
ures will yield satisfactory results in dealing with plum rot. 
Cankers. In Europe trunks of the plum as well as trunks of forest ‘trees 
suffer from canker caused by adistinct species of fungus. As yet we have no 
true proof of cankers dueto these parasites in Ohio. The parasiteis Nectsia 
ditissima. 
Crown Gall. This diseasehas been reported upon the plum as upon the 
peach, but is less frequent. ; 
Leaf-curl. On Japanese varieties of plum, 
the leaves at times suffer from leaf-curl at- 
tacks similar to those upon peach. It should be 
4 Teached by the same remedy, winter sprays. 
Mildew. The powdery mildew fungus of 
the cherry (Podosphaera oxyacanthae(D.C.) 
De By) also occurs at times upon the plum, 
but is usually rather easy to control. 
Pockets or Bladders. American varieties 
of plum are sometimes attacked by a fungus 
‘(Exoascus sp.) related to the leaf-curl fungus. 
This causes enlargement of the young fruits 
which are hollow; because of this condition 
they are sometimes alluded toas ‘‘bladders.”’ 
The conditions which bring about the disease 
are the same as those of leaf-curl, viz, ex- 
- cessive cool wet weather in the early season. 
The winter spray as for leaf-curl should be 
effective. 
Fig. 80, Plum leaf attacked by Shot- Root-Rot. Plums are susceptible to at- 
hole Fongis. “This fungusds the same as tack of root-rot as in the case of other orchard 
that causing Leaf-Spot on cherry, but in ° 
this case the diseased areas of the leaftend fruits where set following timber or fruit 
to drop out, leaving ‘‘shot-holes."” trees that have suffered. 
Shot-Hole Fungus is at times a very de- 
structive disease of the plum. It is duetothe same fungus (Cylindrosporium 
Fadi Karst.) which attacks the cherry, although in this case even more serious 
injury is liable to result than with cherry trees. Where trees are defoliated by 
shot-hole fungus the fruit is of small value and the trees put forth new foliage 
and blossoms, thus leaving immature wood and a sappy condition for trouble in 
winter. Under such circumstances the secondary losses may beenormous. This 
fungus is readily prevented by spraying with standard Bordeaux mixture, the 
first application being made when the leaves are half grown, and two more at 
intervals of about three weeks. 
Winter Injury or so-called Sun-Scald. In 1896-7, following neglected cases of 
shot-hole fungus which defoliated the trees in the fall of 796, some plum orchards 
were almost totally destroyed by the severe winter freezing. The sappy trees 
were not in condition to withstand the severe cold, 15 degrees. Young trees 
were killed to the snow line while older trees had the sides of the trunk, com- 
monly that facing to the southwest, severely injured. Plum trees were again 
injured, by freezing in 1906-7. (See Bulletin 192), The prevention of this trouble 
lies in the prevention of the shot-hole fungus and the avoidance of the conditions 
named. In sorre cases it is possible that protection of the trunk by straw or 
boards might be profitable. 
Rust upon the plum has been collected in some of the western states, but at 
present has not been seen in Ohio by the writer. 
