Q. I have a large Maple tree. Last year small (ball bearing size) round empty bright orange pods started growing in clusters on the leaves. I took a leave to Peninsula Gardens and nobody there knew what they were. When the leaves fell off we raked all of them up off the ground hoping that it would’nt happen again this year. Well, they are all over the tree again. They start out with a pale green color and then turn bright orange. They are hollow. What is on my tree? Gina Forbush – Gig Harbor, WA
A. These sound like tiny galls. Galls are irregular growths that can appear on plants. They can be biotic (caused by insects or microorganisms or abiotic (caused by environmental factors). If you have a red or silver maple most likely cause by an insect called the maple bladdergall mite (Vasates quadripedes). A chemical excreted by the organisms that acts like a growth regulator creates biotic galls. This is because this chemical(s) gives the host cells different “instruction”. Sometimes insects can be found inside the gall since the gall is formed to protect it. In the case of the maple bladdergall mite it is thought to be an enzyme the mite produces when feeding. The female also lays its eggs in the gall. The eggs hatch and the offspring feed in the gall until large enough to venture out on their own. Then new galls are produced where the offspring feed. This year’s offspring are now finishing feeding and will move back into the bark of the tree to hide in cracks and crevices by the end of July. Since the mites are small (less than 2mm long) there are plenty of hiding places on a maple tree. Fortunately the maple bladdergall mite damage does not pose a threat to the overall health of the tree. On smaller trees you can pick off infected leaves and dispose of them to reduce the future population. This will only work if you remove the leaves before they move to the trunk and branches in July. Then in late winter/early spring before bud break you can use a dormant oil spray to smother the overwintering mites. Be sure to get full coverage of the trunk and all the branches.