Hi all, I just moved into an urban home in Portland last fall that has a big plum tree (trunk is perhaps 10 inches diameter and tree is 20 feet tall) that provides a screen between my backyard and a small apartment house. I did notice that the leaves were dotted with tiny holes before they dropped for the fall. During the winter I pulled up the black plastic layers under the tree and replaced it with mulch. In the spring, I pruned out dead wood, suckers, rubbing branches, and branches which headed inwards. I was told not to take more than 20% each year. I hoped that the tree would be much happier and healthier, but alas, it seemed to have made little difference. If the tree feels happier with this attention, it has not communicated it through greater health or productivity, although the spring bloom was pretty. It once again has the tiny brown spots and pinholes in the leaves, which seem too thin and papery, and has only a very little amount of green fruit (which I understand may just mean it needs a pollinator). It had plenty of blossoms. Since it is close to my back neighbor's fourplex balconies and patios (in fact some of what I cut out was actually intruding into one neighbor's balcony by several feet), I am hesitant to do a spray (especially here in Portland). What else can I do to help revitalize my plum tree? fertilizer? bt? I inspected today and don't see aphids and don't know what else I should be looking for. I had thought that because of its size, it should be able to fend for itself for nutrients, but maybe in its current condition I should try a fruit tree fertilizer. Are the holes a fungus or some other disease? I would think a chewing insect would notch the edges of the leaves more than make this little pinholes and this seems like it is the brown spots that are just maturing and dropping out, leaving the holes. Can anyone give me advice as to what to do please?
I'm no expert, but this article may be of some help for you: http://www.gardeningknowhow.com/problem ... fungus.htm
I talked to the master gardener service and they said basically the same thing as this article. It is a fungus which can be controlled by spraying with bordeaux in the fall, but there is nothing I can do this time of year other than keep leaves cleaned up and make sure the tree has enough air circulation. It is throughout all the leaves on a large tree, so not an option to "remove infected leaves" but I guess I'll figure out what Bordeaux is and go forward.
I too have a plum tree with shothole. I read the article and it corresponded with the conditions my tree has to deal with (soaking wet Clackamas County OR). I will be spraying it next fall, like you. And pruning to remove anything that looks "funny" to see if I can save it. The article did give treatment suggestions but it didn't sound too optimistic about success.
The only thing I do know is the answer to your question about bordeaux mixture. It's a fixed copper spray, I mixed mine using the copper sulfate powder; you have to be cautious with mixing it so it doesn't aerosolize - you could breathe the dust. I used to use it on two peach trees that committed suicide - I was not able to control the leaf curl. But one year I sprayed leftover Bordeaux mix on a wimpy apple tree that seemed never to be healthy and the following spring it was a miraculous result. The apple looked gorgeous.
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