Some of the oak trees in our complex are infested with powdered mildew and it looks like it is spreading. The trees are about 13 years old. Is there anything that can be done or do we just have to wait and see what happens. I would appreciate some info please. I have never seen it on such big trees. Thank you. Babs
English oak (Quercus robur) prone to this. Soaking the roots might help a little. Spraying would probably have to be done before it appeared and would have to cover the whole tree, quite an operation if these are at all large.
Thanks Ron, yes they are quite large. Our garden centre in town thinks they might have to be cut down eventually. Is that so? or do they get healty again? Thank you again Babs
Your garden centre does not have a clue, they should be ashamed of themselves for even suggesting that the trees may have to be removed. Assuming that the trees are otherwise healthy then one year of powdery mildew is not a problem. If there are other problems with the trees then looking at improving tree health. This means improved soil conditions via decompaction (air spade maybe), addition of mulch and compost, application of compost tea to soil and leaves and maybe pruning if dead wood is present. Healthy soild make healthy trees which are better able to withstand disease and insects.
Agree with mrtree. The nursery are probably hoping to get some work in planting replacements! Powdery mildew on English Oak is common here where it is native, and it doesn't do any significant harm to the trees.
Many mildews appear in summer because that is when conditions suit them. Only thing I would do to soil that might seem to be relevant is re-moisten it. Repeatedly spraying tops of trees (in morning) with water might also have some effect. Many (most?) mildews are favored by leaves being dampened, as when moistened by summer fogs or dews, but are inhibited by washing. http://www.puyallup.wsu.edu/~Linda ...al Myths_files/Myths/Compost tea 3rd time.pdf
