Galls are abnormal growth on plants. They are caused by the feeding of living organism, most often insects, but also bacteria, fungi, nematodes and mites, on the plant. Although these growths may be unsightly, they usually do not affect the health or vigor of the host plant.
|Galls on red maple caused by mites.
||Eyespot gall on red maple.
||Poplar twiggall fly: pupa emerging from gall.
|Corky bark disease on quaking aspen.
||Blade spruce gall adelgid.
|Leaf gall caused by Eriophyid mite on plum/cherry.
||Oak apple gall.
||Galls on oak.
Click on images to view full-size
Identification and Control Information (each will open in a new window)
- From the Maine Department of Conservation, Maine Forest Service:
- Gall Mites of Deciduous Shade Trees [HTM][PDF]
- Maple Bladdergall Mite [HTM][PDF]
- Balsam Gall Midge [HTM][PDF]
- Cooley Spruce Gall Adelgid [HTM][PDF]
- Eastern Spruce Gall Adelgid [HTM][PDF]
- Galls on Shade Trees and Shrubs [PDF]—Purdue University Extension
- Insect and Mite Galls [PDF]—University of Minnesota Extension Service
- Insect and Mite Galls [PDF]—Colorado State University Extension
- Insect Galls [PDF]—University of Florida Extension
- Galls on Plants (Oak Apple Gall, Oak Hedgehog Gall, Gouty Oak Gall, Maple Bladder Gall, Maple Spindle Gall, Ash Midrib Gall, Cooley Spruce Gall, Goldenrod Ball Gall, others) [PDF]—Cornell University Insect Diagnostic Laboratory
- Nature Trivia: Plant Galls (lots of good pictures)—Henderson State University
- Bacterial Crown Gall on Ornamentals in the Landscape [PDF]—The Ohio State University Extension
- Gallery of Common Galls—NC State University, Department of Entomology
- Entomological Notes: Galls on Oak [PDF]—Penn State College of Agricultural Sciences Cooperative Extension
[Photos, left to right:
Steven Katovich, USDA Forest Service, Bugwood.org; Clemson University - USDA Cooperative Extension Slide Series, , Bugwood.org; Whitney Cranshaw, Colorado State University, Bugwood.org; William Jacobi, Colorado State University, Bugwood.org; Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org; Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org;
Steven Katovich, USDA Forest Service, Bugwood.org;
James Solomon, USDA Forest Service, Bugwood.org;
John H. Ghent, USDA Forest Service, Bugwood.org]
|It is the policy of the State of Maine to minimize reliance on pesticides. The Maine Department of Agriculture and the Maine IPM Council encourage everyone to practice integrated pest management and to use pesticides only as a last resort. The mention of pesticides in the fact sheets linked to these pages does not imply an endorsement of any product. Be sure that any product used is currently registered and follow all label directions.