Hello! I'm hoping someone can help point me in the right direction. Sorry for the long post - I want to provide as much relevant detail as possible.
Last year I planted a Lapins cherry, bare root, on Gisela dwarf stock. It grew happily to about 1.5m and dropped the last of its leaves in November, then overwintered fine. The cherry was late to flower, but so was everything else around here (snow in April is depressing). When it flowered, it flowered happily, and set about two dozen fruit. I hemmed and hawed over whether to pinch the fruit, but figured the tree would know when it was ready. The tree leafed out fine.
The tree is in a spot very sheltered from north wind and moderately sheltered from west and east winds. The soil here is nice and rich with good drainage, sandy after you dig down enough. The tree is set back from the road - no chance of road salt damage - in the middle of a small lawn, but the lawn has been dug away from the tree to past the drip line of the cherry tree. The tree is mulched, but I've been sure to keep the mulch from touching the rootstock.
Recently we had a hot, dry spell (over 30 C, no rain). The lawn around the tree scorched, and I debated whether to water the cherry as I read that they really don't like wet feet. I noticed some of the leaf clusters on the lowest two branches turning yellow - starting at the tip of the branch, and moving down as the days passed. The branches themselves did not appear discoloured or unhappy. I watered, figuring the tree was dehydrated (other trees in the area have discoloured and dropped leaves, too). The leaves are less droopy, but the leaves on the two lowest branches continued to turn yellow, sometimes a bit orange, and drop. A few leaf clusters stayed on the branches and browned.
I started reading up on it online, which I've learned is like self-diagnosing a human illness. It seems my little tree could have any number of entirely pedestrian, or totally terrifying issues.
A neighbour thought the cherry could have fire blight as some of the leaves turned orange. I looked that up, but none of the leaves have turned black, and the branches never shrivelled or discoloured.
There are no cankers, no oozing sores. The tree has no wet, soft, or brittle spots. It has no holes in the trunk that I can see. The leaves had no aphids or other bugs on them. There are no unusual growths.
I thought maybe it's verticillium as the die-off started with the bottom leaves - and because I like to panic. But, if I'm correct, verticillium would have killed from the trunk out, not from the branch tips in? I may be totally off-base about that...
So, just to be safe, I carefully pruned the two possibly infected branches back 30cm from the possibly infected leaves. The branch cross-sections showed no discoloured rings, which would have suggested something like verticillium. I peeled back the outer bark, and there were dry, brown (not grey, not black) spots on the inner bark around the sites where the now-dead leaf clusters were. The rest of the inner bark was green.
Am I panicking here? Is this just a stressed tree that will bounce back? Should I pinch off the fruit and give it another year before I let it produce? Or could this be something I should be copper spraying/neem oiling/destroying the tree before it spreads some horrible disease to the rest of my plants? Thanks for your thoughts, and sorry for the wall o' text.
Thanks! I've done my best. Because I already pruned the tree, I had to dig the potentially diseased bits out of the trash...
The first picture is of the whole tree. The perspective makes look a bit off; all the leaves are about the same size.
The second picture is of the tip of one of the branches I pruned. Again, this is more than 24 hours after being pruned.
The third picture is of the same branch, where I peeled the outer bark away. Previously it was only brown around where the leaf bud meets the branch (sorry if my terminology is off). The rest was green. Now it's all the same brown colour.