My guess, sadly, is Pear Psylla. How old is the tree? What rootstock is it on? Has it occurred before? What is the overall health of the tree?
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Thanks everyone for the feedback! I should’ve probably given more background information. The tree is a new Ambrosia pear I bought from Gurney’s. It was bareroot, and on calleryana roots. I sprayed it with Kocide while it was still dormant when first planted. Our weather has been all over the place the last 2 months, but it has been mostly mild to very warm, and we’ve lacked good rain all spring. I haven’t observed any noticeable bugs on it even with a magnifying glass.
I went and sprayed it with streptomycin to see if that helps. These are pretty bad prospects for it surviving longterm here if fireblight is the problem. None of my other 10 pear trees have had any strikes yet this year 
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With a little luck, if it is pear Psylla it came infected. Hopefully theyll cycle out and not come back. They are so small, to see them you need a magnifying attachment.
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@Richard @7catcmom I think you guys were right about fireblight. The streptomycin spray I applied seems to have stopped it. It isn’t getting better but isn’t get worse at least. Maybe it’s working on its roots for the time being.
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Look like Euro pears have started to give you a headache, Andrew. The blight on this variety and the issue with Harrow Sweet fruitlets.
My Potomac pear also has similar disease symptoms as Harrow Sweet. Glad I have 7 Asian pear trees that seem much healthier. All are carrying a huge load of fruitlets so far.
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Will you be about to send sample to Penn State extension service for diagnosis? It would be good to find out for sure what was the cause.
I used to think growing pears was easy.
That’s a good idea. However, I wonder if my sprays will affect their ability to identify the pathogen(s). It might make things harder if I killed it off.
East Asia is more of a climate cognate to East NA than Europe. Sometimes I wonder if the Asian pears are more adapted to East NA environment than Euro pears.
Something along those lines was mentioned in this article about growing Asian pears in the Mid-Atlantic. @sockworth
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At least from the look of the damaged Harrow Sweet, I wonder if Penn State lab could tell if it’s scab, blossom blight or other pathogens.
You could let them know what chemicals you sprayed the fruitlets and the leaves with.
I wonder if @scottfsmith has encountered this issue. He has Harrow pears and lives quite close to you.
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Thanks for mentioning this, I’m beginning to think I need to get rid of my European pear ambition, if I can get one Asian pear to fruit, I would be happy.
In my experience asian pears are as hardy as European pears but not hardier. Hybrids of both and other pears such as hybrids of siberian are hardier than all the others. When new genetics are introduced some wonderful things come out of the mix. Southern pears like kieffer, ayers, hood etc. are hybrids. They are far more resistant to fireblight. There is signifigant effort being put into testing in that area https://extension.psu.edu/a-new-fire-blight-resistant-pear-bell
https://www.ars.usda.gov/ARSUserFiles/20721500/catalogs/pyrcult.html
Pyrus bretschneideri an interspecific hybrid of Pyrus pyrifolia x Pyrus ussuriensis
Normally when i see blackened tips of a tree it is one of several things eg. weather issue excess wind, sun or water, bacterial damage such as fireblight, fungal damage, or insect damage. If you sprayed for fungus and insects we can eliminate those 2. Fireblight would progress or not in 17 days. That leaves weather related issues. Considered other possibilities that were brought up, which is an insect resistant to your management. That is possible but unlikely if you have a good management system. Last year i received fireblight strikes on my harrow delight and harrow sweet has got them before as well. They are specifically bread to handle fireblight. Last year i was interested in the disease progress on the tree. The disease made it 8" on the tree and stopped. First sign of infection looks similar to your issue but progressed rapidly. Harrow sweet as sn example is highly resistant to psylla. Do you have a current picture?
25 Harrow pear varieties
What was the fresh cut im seeing in the photo? My guess is the ambrosia fell into one of the possibilities i brought up. Most of my orchard is highly disease resistant. I discussed thoroughly what penn state pear research had resulted Bell Pear aka US84909-391 . I would highly recommend looking at these varieties in the highly fireblight resistant type.
California weather cognate is more like coastal western Europe (Portugal for example).
The study @PharmerDrewee linked was in Maryland–in east coast USA it’s way more humid and rainy than California in summer.
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I may have the same problem here. I’ve already got one Asian pear tree dead because of fireblight, in fact that’s how I discovered growingfruit in the first place. I think I stick to grow something that will grow here without spraying, or shall I say I pare down my pear ambition, growing pears is a pain here.
Sure, a lot of local factors are at play as well. Sources for disease could be greatly magnified based on what’s being planted in your immediate surroundings by neighbors.
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I’m the only one who has a lot of fruit trees here.
There’s are many ornamental trees that share the same disease / pests as fruit trees.
Once the disease / pest establish a life-cycle in a location, it could stay there indefinitely coming back every year as long as its required hosts are alive.
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