Lumps on leaves and bumps on stems have your landscape plants looking like something from a horror movie.
No need to worry about these bizarre growths, they are just the plants’ response to insect feeding. As leaves and twigs expand in spring, mites, adelgids, psyllids and other insects feed on them causing a proliferation of growth. The plant forms these fuzzy red patches, tall green spindles, orbs and other strange often colorful growths that encapsulate the insects.
These galls are not harmful, just annoying to the gardener. So there is no need to treat. In fact spraying when you see the galls does no good since the insects are safely protected inside the gall.
Weather and natural predators will help keep these gall causing insect populations under control in the future. So relax and let nature take care of this pest for you.
A bit more information: Crown gall on euonymus is an exception. These gall appear near the base of the stems on the euonymus. The growths are caused by a soil-borne bacteria. As the galls grow, they weaken the stem and can cause stunting and tip dieback. It is believed that this bacterium also causes galls on forsythia, viburnum, highbush blueberry, American elm, hickory, maple, oak, and privet. The only control is pruning beneath the gall and disinfecting your pruners between cuts. Unfortunately, this usually means ground-level pruning since the galls most often occur at the base of the stems.
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Ebert's Greenhouse Village
Wisconsin State Fair
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Mequon Nature Preserve