How large were the plums when you sprayed them? Were the small fruit bigger than a marble? Smaller? If bigger than a marble, how much larger? Did 100% of the fruit drop? 50%? More or less than that?

Also, was the tree carrying a heavy load of fruit and, if so, had you thinned the fruit yet? Do you remember how much time had elapsed between the petal fall of the flowers and the time you sprayed?

Finally, did the fruit look perfect or did you see black marks or scars on some of it?

Also, around the time you sprayed, or after you sprayed, did your temperatures drop down to or below freezing?

I have a couple of ideas for why this might have happened but need my questions answered so I can narrow down the possibilities. I have grown both Ozark Premier and Methley here since either 1999 or 2000 and all the fruit does not spontaneously abort like that without a good reason. We just need to narrow down the possibilities for what the reason might be.

The plums were 1/2 size of marbles, and as these trees were just planted last spring barefoot and was nice shape and root system was very fiberous. They seemed to have a nice crop but over abundance. Now my peaches l have thinned!

Here is a Grey area, just can't remember if I sprayed before petal fall. No black marks but this spray was well after young plums were formed. No freezing night's here, just 40 miles north of Durant, peach's and apples just fine.

Thanks Bob

Plum trees are notorious for dropping fruit and sometimes it is hard to figure out why it occurs. With Santa Rosa, in particular, there are years where it seems like every single flower was pollinated and set fruit and you have to thin aggressively. In a great plum year, I've had to remove 90% or more of the Santa Rosa plums when thinning.....and I'm talking maybe 2000 tiny plums were thinned off one tree. It took me forever to get it done. I'd rather have a couple hundred big plums than 2000 tiny ones that are mostly all pit and no meat. If you don't thin the fruit, the tree eventually will thin the fruit itself to some degree because it knows when it is carrying more fruit than it can support. Having said that, I do not necessarily think that is what happened to your plant because mine don't start aborting fruit until they are about the size of green seedless grapes if I haven't started thinning them yet.

Sometimes plums drop due to a lack of pollination. Santa Rosa is at least partially self-fruitful but sets fruit better with pollination from the flowers of another variety. The fact that your fruit dropped while so young and small might be an indicator of a lack of pollination or of only partial or incomplete pollination.

Since your peaches and apples are fine, I agree with your assessment that it wasn't freezing temperatures.....and I am west of you in Love County, midway between Marietta and Thackerville. We haven't had any temperatures here cold enough either to cause the fruit to abort and we are in a cold microclimate where late cold spells often knock off the fruit, so I would have expected it to happen to my fruit more so than yours, and it didn't even happen to mine.

The reason I asked about black or maybe brown spotting or scars on the fruit was that I was thinking it might be plum curculio damage. To prevent that, I believe you have to spray at or just after petal fall but I garden organically so lack experience with the use of those chemicals, having never used either of them. I've never sprayed my trees with anything and don't have plum curculio damage so am relying on my memory of plum curculio damage on my family's plum tree from back when I was a kid and my dad did spray some years but not others.You can look at the aborted fruit to see if you see the little brown sort of crescent-shaped scars that are indicative of plum curculio.

Because it happened after you sprayed, I can't help wondering if the two are linked, but I've never heard of that happening before, and some of the other local gardeners who live near me spray their plants every year and it doesn't knock their fruit off the plum trees.

This is just a guess, but it might be the young age of your plum trees. My plum trees dropped all of their fruit the first 2 or 3 years and I wondered if that was because the trees just weren't mature enough yet to support a heavy load of fruit. Since then, I've only lost fruit to late freezes, large hailstones or strong winds in excess of 50 mph when the fruit was still small and hadn't been thinned yet. I don't think peaches drop fruit as much as plums do, so that would explain why you saw the fruit drop on one type of fruit tree but not another. Sometimes it seems like plums drop their fruit if you look at the trees funny and offend them----that's how prone they are to drop fruit. In some parts of the country it is called June drop or June fruit drop, but our trees are much earlier here and it is more common in April or May in the years when it happens. It could be just a coincidence that the fruit dropped after you sprayed.

If you want to talk to the fruit tree experts to see what they say, go to the Fruit and Orchards Forum here at Garden Web and ask your question there.