I did a successful espalier of asian pear 4 variety but this summer orange dots appeared on leaves. Now turned spiky orange with white tips. What is it and what should I do. As can be seen from pics did not affect production of larve fruit.
What you have is Pear Trellis Rust, a fungus disease with pears and junipers as alternate hosts. Someone is likely to have a juniper hedge nearby. There is not a lot that you can do about it, unless you can find and kill the junipers. However, I've found that Asian pears are not bothered by this disease to the same extent as European pears. I have an Asian pear on which I grafted a branch of D'Anjou Pear many years ago. It grew well until a neighbor planted a juniper hedge. After that, the D'Anjou Pear leaves were practically covered with the fungus; and the grafted branch practically died. The Asian pear part of the tree showed scattered signs of fungus on the leaves, but continued to grow and produce fruit. I cut off the D'Anjou Pear graft and haven't tried to grow any European pears since then. So, I expect that your tree will tolerate the presence of Pear Trellis Rust, although it might help to pick off the worst affected leaves.
I was reading on an earlier thread that monthly treatment through the summer with a copper-based fungicide may help to reduce the severity of pear trellis rust, though it won't stop it entirely. I have a 20-year-old Bartlett pear tree that gets orange spots on roughly 20% of the leaves most years; I first noticed this problem about 5 years ago. I use a dormant spray every February, I top-dress with about 1/2 inch of compost each year and use just 2 fruit tree fertilizer spikes each spring rather than the recommended 3-4 per tree. I've been picking off the infected leaves and throwing them in the garbage about once per month, and something must be working because I'm getting quite a lot of nice fruit every year. I have one juniper in my front yard, about 30 m away and on the opposite side of our large house, and it shows no sign of any problems. I haven't seen any other junipers within several blocks, though I suppose it's possible that someone may have one in a fenced back yard that I can't see. I wonder if there is any down-side to spraying the copper-based fungicide once per month, but I'm inclined to try to see if it helps. I haven't seen any for sale in local garden centres, though it is readily available in Bellingham and I don't see any regulations prohibiting the use or sale of it in Canada.
