Posts Tagged "Bumps on maple"
Maple Gall Mites
A common concern with maple owners is Maple Gall Mites, tiny little red or green balls on their maple leaves. According to the University of Wisconsin, “Maple leaves frequently develop growths or swellings known as “galls”. These are caused by microscopic mites. The form and color of the gall indicates which species of mite is the culprit. If a tree is heavily infested, its foliage becomes distorted and drops prematurely. But usually the injury is only temporary, and the tree’s vigor does not deteriorate significantly.” Maple Galls can be noticed in early May as a green color, eventually turning into a pinkish red and finally into a black.
Red Maple Gall Mites on Maple
What do the mites do?: The adult mites become active very early in spring, just as buds begin to open. As they feed on the developing leaf tissue, growth regulating chemicals produced by the mites interact with plant hormones causing an abnormal stimulation of cell growth. This abnormal growth forms the galls that gradually enclose the mites. Each mite species produces slightly different substances, resulting in the different characteristic gall shapes. The mites get nutrients from the inner gall tissue and are protected from natural enemies (University of Wisconsin).
How many types of gall are there?: There are three types of gall; maple bladder, maple spindle, and erineum gall mites.
How can I control Maple Gall?: Although control is not required, and damage done by maple galls is neither significant and/or long lasting… the following are options a tree owner can take (Ohio State University)
Strategy 1: Use Resistant Maples – Norway maples and some of the named cultivars of maples with outstanding red or yellow leaf color appear to be resistant to these gall mites and midges. Talk to the plant supplier to see if the tree cultivar has a history of leaf gall problems or not.
Strategy 2: Dormant Oils – Use of dormant oils on maples is discouraged because leaf and twig damage can result unless the tree is truly dormant. However, some reports of success have been made where the trunk has been drenched with dormant oil to kill the overwintering stages of the bladder gall and spindle gall mites.
Strategy 3: Standard Insecticide/Miticide Sprays – Several insecticides and miticides are registered for control of gall mites (eriophyid mites) and gall midges. If these products are to be used, they have to be applied precisely when the new leaf buds are opening. Most sprays have little, if any, effect because the window of opportunity is very short. Once the gall has formed, it is too late to make an application.
Strategy 4: Systemic Insecticides/Miticides – Several systemic pesticides (sprayed, soil injected or trunk injected) have been recommended as useful in controlling these gall forming pests. However little evidence of success has been found in the current literature. Once the gall has formed, it is too late to make an application.
Resources and Additional Reading: http://learningstore.uwex.edu/pdf/A2691.pdf, http://ohioline.osu.edu/hyg-fact/2000/2004.html, http://www.ca.uky.edu/entomology/entfacts/ef404.asp, http://www.hort.wisc.edu/mastergardener/Features/insects/maplegallmite/maplegallmite.pdf, http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note04/note04.html