EXPERIMENT STATION BULLETINS. 309 



After the spots have turned brown the winter spores are formed, but 

 they do not become fully developed until the following June, when they 

 are found in pustules on the under side of the leaves in elongated asci or 

 spore cases. 



When a leaf has many spots upon it they run together and thus destroy 

 a large part of the tissues. As a result, the leaves drop and the fungus has 

 thus not only robbed the tree of much of its nourishment, but it has deprived 

 it of the ability to assimilate and prevented it from ripening its wood. 

 As the fungus works entirely within the tissues, all remedies must be 

 preventive, but the use of fungicides has been found even more efficacious 

 than might be expected, as Bordeaux mixture, applied as recommended 

 for the rot, will keep the trees free from leaf-blight. For the cherry and 

 plum trees that are not in bearing, it should be applied in July, some- 

 where about the middle of the month and again about the first to the 

 tenth of August. Had this remedy been employed for the past five years, 

 not only would the lives of thousands of plum trees been saved, but the 

 growth of others would have been largely increased. 



PLUM POCKETS {Taphrina pruni, Fckl.). 



The so called "plum bladders " or "pockets" are due to a parasitic fungus. 

 It causes the fruits to enlarge and become hollow, and finally drop to the 

 ground. It is also quite common upon the branches of American varieties 

 of plum, causing swellings to form upon them. 



The fungus is carried over winter in the winter spores in the diseased 

 fruits and branches, and these should be collected and burned. The spring 

 application of copper sulphate will also do much to head ofp the disease, 

 and by the occasional use of Bordeaux mixture during the summer it can 

 be held in check. 



Of the other diseases of the plum, brown rot is most troublesome. 

 It has been described at length under the cherry and peach upon 

 which it also appears. The work of the fungicides can be greatly aided if 

 the diseased fruits are collected and burned. 



Leaf rust or blight, which sometimes attacks the leaves of the 

 plum and causes them to fall during hot, dry summers, is the same as upon 

 the peach {Puccinia pruni-spinosce) . It shows first as small, yellow spots, 

 which soon cause the remainder of the surface to turn yellow and finally 

 brown and they then fall to the ground. The use of fungicides as recom- 

 mended for leaf-spot will generally be sufficient to hold it jn check. 



:Z. INSECTS OF THE PLUM. 



Besides the plum curculio, spoken of under cherry insects, the plum tree 

 suffers considerably from 



THE PLUM-TREE APHIS (Aphis prunifolia Fitch). 



The life history of the plum aphis is similar to that of those on the apple, 

 cherry, and peach which have already been spoken of. When numerous the 

 lice do considerable injury, as they do not confine themselves to the leaves 

 but feed on the tender twigs and stems of the fruit, drawing so much sap 



