Jeffrey Turner wrote:

EV wrote:
Pat Kiewicz wrote:
EV said:

The prune plum is a whole other story. ...
Last year it bore heavily, but dropped about a third of it's fruit
before it ripened. I lost half of what was left to various bugs in
various stages. And some of the fruit had what looked like crystallized
loops and nubs and dribbles of sap on them. What is that?

This year the tree fruited even more heavily, but has dropped about 2/3
of its fruit, either green and shrivelled, purple and shrivelled, or
purple and hard. The crystallized stuff is on many of them too, and I
can see bumps and punctures on much of the fruit. If I get a dozen
edible plums, I'll be lucky. So much for the plum jam and the galettes.

Where are you located? In eastern North America this is most likely
plum curculios, a type of weevil.

I'm in Toronto, Ontario.

http://ohioline.osu.edu/hyg-fact/2000/2043.html

It's one of the few bugs I haven't seen in the garden this summer. Lots of Black
Vine Weevils though. Had a bunch of pear slugs on the cherry after it bloomed and
removed them all by hand.

Just a guess, but the bumps may be some type of scale insect.
The crystallized stuff might be "honeydew," their excrement.

Thanks for your comment.

Actually, I have seen scale insects, I think, here and there, but the bumps on the
fruit seem to be under the skin. I think that the crystallized stuff is too big to be
honeydew. I've put a picture of it up he

http://www3.sympatico.ca/great/viralbynature.html

That one's up near the fruit stem, but they can be anywhere on the fruit.

I've gathered a few fallen fruit specimens and will 'autopsy' them to see if there are
clues inside. :-)

EV