I found mature worm and little young worm inside my plum, I assume they both are PCs. Couldn’t think other worms burry inside of plum besides the PCs. It looks like the young worm hatched not very long a ago. If assume PC life cycle is roughly 2 month then the mature worm should come from the eggs deposited in the plum sometime in June. But the young worm looks just a week old so, it should be deposited sometime in July. Will its parents be the first generation of PC? I read somewhere PC only have one generation a year in cold area. If it is OFM, will OFM started in July?
Did they crawl away or roll around. If they crawled, they are OFM. With this late damage, I would suspect OFM. My 2n OFM attacked my trees about 2 weeks ago.
PC has only one generation in colder zones in ours. In my area OFM has 3 generations. I guess your area may have at least 2-3 generations, too.
I do have PC and OFM attacking plums. In fact, some years, some of my plums had both types of worms inside.