Foliar damage on a none bearing fruit tree needs to be severe to have any effect. Like 50% leaf loss. So unless it gets worse do nothing. But of course check for the culprit and try to decide if it's likely to get worse.

Okay, so just let it do it's thing. Any idea when it'll start bearing fruit?

Yours is likely to be Euro plum. Some are self fertile, some not. If not, do you have another compatible plum to cross pollinate?

Some plum can bear in year 3,. Some a lot longer. What variety is yours?

Our Santa Rosa had fruit this year, about 20 plums and we planted it bare root last year

I just checked there tonight and if my Japanese is correct its labeled "Sugar Prune", fruit matures mid August - late Sept., purple reddish color, does not require cross pollination.

Sugar plum is a Euro plum. In general, most Euro plums take longer time to fruit.

Thanks. I'll try to find a better ID on the variety. Online research seems to indicate there's a very strong showing of Japanese varieties, perhaps this is a Japanese original variety?

Took a closer look at the tree tonight, and it looks like the laugh is on us. Somewhere along the line I think the rootstock took over and the original tree is dead.

Then, go with plan B, grafting preferred varieties on the rootstocks.

Yes, good idea, I now have 2 tough plum rootstocks - 1 here and 1 from a failed peach tree. I'll have to make that new skill jump sometime. Is there a decent simple guide for someone with zero knowledge on grafting?

Alternately, if I cut off all the rootstock growth now (substantial), will it force the leafless plum grafted to it?