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Ash Flower Galls |
Question:
The extension brief on this topic suggests that ash flower galls remain on the trees for two years. Do the galls return? If so to what degree?
Minnesota Master Gardeners say:
I believe what this means is that the mites that infest the flowers on a male ash tree in one season, may remain in the resulting galls that form for up to 2 years (overwintering there). That does not mean that after 2 years your tree will have no more galls. Typically, insect pests have cycles in which some years they are at a peak population and other years they are less prevalent, so you may see fewer galls forming in some years. If you have had ash galls mites infest your tree in the past, you will probably always be plagued with them to some degree. Even if mites are not present in one year, you may have residual galls remaining on the tree as an eye sore, unless you can prune them out. Mites can only be battled if you spray your ash tree annually 7-10 days before flower buds are expected to open; this is not so easy to time. Recommended products are carbaryl, dicofol, or horticultural oil (always follow the label and check that ash is one of the plants listed).
The Extension publication Insect and Mite Galls in the Landscape is at: http://www.extension.umn.edu/distribution/horticulture/DG6704.html