474 INSECTS AFFECTING VEGETATION 



formly gave growths of a yellow motile organism, thus showing bac- 

 teria to be the cause. Dr. E. F. Smith states that the disease also 

 occurs on the leaves forming numerous small water-soaked spots 

 which finally may end in shot holes. (Conn. E. S. Report, 1905.) 



While the disease in its present condition is not very serious, 

 one can not assume that it will remain so since it may spread to 

 other varieties and become more virulent. Though of bacterial 

 origin, it is quite different from the bacterial blight that has been 

 found occasionally on the plum and commonly on the pear, etc, 



Plum Pockets. This disease on account of its very character- 

 istic and striking symptoms has long been known to horticulturists 

 and others. It is very widely distributed throughout the United 

 States. The vegetative portion or mycelium lives over winter in the 

 younger twigs and grows out into the developing ovaries in the 

 spring. All or most all of the parts of the ovary are affected and 

 the action of the fungus is to greatly stimulate the tissues of the 

 ovary so that a very rapid growth takes place. The result is a much 

 swollen, somewhat irregular and spongy body of light yellowish or 

 white color. No stone is developed in this plum-pocket but the cen- 

 ter is hollow or frequently traversed by loose threads of torn tissue. 



The leaf buds and young twigs may also become modified by 

 the action of this fungus to form very irregular spongy swollen ob- 

 jects. In this case the resulting hypertrophy varies with the stage at 

 which the fungus begins its work. If the leaves are not far developed 

 when attacked their normal form may never be attained, but the 

 hypertrophy may affect only a portion of the leaf if its attack is 

 made upon the leaf when partly grown. 



This disease is produced by the fungus Exoascus pruni a spe- 

 cies somewhat closely related to the one causing the leaf curl of the 

 peach. No special spraying treatment can be recommended, though 

 the use of Bordeaux mixture would no doubt reduce the chance of in- 

 fection. Diseased fruits, buds, leaves and twigs should be removed 

 and burned. (Ala. E. S. B. 132.) 



Plum Rot. This 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* 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 thor- 

 oughly. Likewise, control the curculio. No halfway measures will 

 yield satisfactory results in dealing with plum rot. (Treatment 

 Same as for brown rot of peach.) 



Shot-Hole Fungus. This is at times a very destructive disease 

 of the plum. It is due to the same fungus f 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- 



* Manilla fructigena Pers. 

 ICylindrosporium Padi Karst. 



