"Plum pockets is another fungal disease that can infect the Japanese-type plums. Infected trees will produce abnormally large misshapened, bladder-like fruit with thick, spongy flesh. The centre of the infected fruit is hollow due to failure of the young seed to develop. The best way to describe the fruit is that it looks like large pea pods. Infections also occur in April as the buds swell and bud scales separate. A spring fungicide application prior to bud swell will control this disease. The fungicide thiram 75WP @
6.75 kg/ha is recommended for commercial plantings with Japanese plum varieties. Lime sulfur can also be used for those persons that have only a few plum trees."From:
formatting link
hope this helps. Sorry I lost the post to reply to.