Kew York Agricultural Experiment Station. 203 



Gum Pockets 'in the Fruit. — The plum like tlie otbei* 

 stone fruits is often subject to gumming, due to various causes. 

 We have observed only one case which is worthj- of mention. 



During the past four years the fruit on five prune trees in the 

 vicinity of Rochester has been seriously affected with gumming 

 as follows: The trouble begins about the middle of July, It 

 first appears as an irregular spot of a darker green than the nor- 

 mal color of the fruit skin. The spots vary in size, but are usu- 

 ally from one-fourth to one-half inch across, with somewhat 

 indefinite outline. In the early stages the skin of the fruit is 

 unbroken. The tissue underneath is brown and there is a rift 

 or cavity filled with liquid gum. At this time, the discolored 

 tissue has no communication with the pit or with the outer 

 world. Frequently, gum continues to collect in the cavity until 

 the skin bulges prominently. The bulged portion is circular in 

 outline. Finally, a crescent-shaped crack, like a curculio wound, 

 appears at the boundary of the bulge and the gum exudes. The 

 exuded gum hardens and stands out in large drops as on curcu- 

 lio-infested fruits. A conspicuous bulge indicates a large gum 

 pocket. After the exudation of the gum the bulge subsides. In 

 some cases there is no bulging of the skin and no exudation of 

 gum. In advanced stages the skin often takes on a purple color, 

 and one-half or more of the fruit may be involved in disease. 

 Then the injury extends to the pit; in fact, the gum pocket may 

 be in actual contact with the pit. Within the fruit the diseased 

 portion is very irregular in outline and not sharply separated 

 from the healthy tissue. Spots may occur on any part of the 

 fruit but are least common about the stem end. The affected 



« 



fruits show a tendency to fall prematurely and those which do 

 ripen have hard spots in the flesh. The disease never takes the 

 form of soft rot. 



The five trees were heavily loaded and almost every fruit was 

 affected at the time of our visit, July 20, There were no gum 

 pockets on the trunk or branches and no gum exudation of any 

 importance anywhere except on the fruit. The trees were 12 

 years old and standing in a garden where the soil was a rich^ deep 



