Iowa State University Extension & Outreach pamphlet number ENT 0039 has been revised and expanded to include color photos of the most common insect galls found on trees and shrubs in Iowa. The hundreds of unique galls are distinctive swellings or abnormal growths of leaves, stems, twigs, branches, trunks and roots caused by insects and mites present on the plant at the time of tissue development. Galls cannot be cured after they have formed and identifying common galls is an important step in recognizing that galls do not generally affect the health and vigor of trees and shrubs.
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