By Jodi Zirbel
What does it look like?
Incredibly small, Eriophyid mites are 1/100 of an inch long and typically require a microscope or hand lens to see them. Although color varies, most types of Eriophyid mites are white or yellow, feature an elongated body, and have two pairs of anterior legs.
Host material and range
Eriophyid mites describe several species of mites, all of which are plant parasites. Named for the type of damage they inflict on the host plant, the Eriophyidae family includes gall mites, bud mites, rust mites and blister mites. These mites are found in all parts of the United States and feed on both coniferous and deciduous trees and shrubs.
In addition to using the wind as transport, the mites also rely on birds and flying insects to move from plant to plant. Closer to the ground, the mites rely on people to move infected plant material into and throughout the home’s outdoor landscape.
Although Eriophyid mites rarely cause plant death, their presence does result in unsightly damage. The mites invade plant cells and feed on the plant’s cellular content. As a result, the plant forms a protective tissue barrier in the area where the invasion occurs, resulting in a gall or other abnormality.
Every plant responds differently to the type of mite invading it. In addition, because the mites are so minute, the infestation is normally detected by the type of damage caused rather than the mite causing it.
For example, the most prevalent Eriophyid mite, the gall mite, causes individual galls that serve as protected areas where the mites can feed. Depending on the type of mite, the gall can be a variety of shapes and sizes, and some are even covered with hairs. On the contrary, bud mites feed on the fruits and developing buds of fruit trees, causing the buds to swell and the fruit to be deformed. Still other mites, as a result of their feeding frenzy, cause the leaf surface to blister.
Most plants can handle large populations of mites, so their presence is rarely fatal. However, plant deformities and leaf stunting are likely to occur.
Preventative treatments aren’t usually recommended, however a variety of techniques can be employed once damage is detected.
Very often, one of the best ways to control Eriophyid mites is by removing and subsequently destroying infected plant material. When inspecting trees and shrubs, look for leaf blistering, bronzing and galls. If detected, prune the infected areas and use a horticultural oil to kill the over-wintering female mites.
Pesticide applications are rarely recommended to treat Eriophyid mites because the treatment window has often lapsed by the time feeding damage has occurred. However if an insecticide application is used, look for products containing abamectin. Plan for foliar treatments of abamectin in the spring about a week before the buds break. Another option, if the preference is not to spray, is the use of a trunk injection application containing abamectin.
Once the damage symptoms appear, plan treatment options for the following season. In addition, a late-season application of horticultural oil may control adult mites ready to over-winter, and help limit the number of plant abnormalities the following season.
What can you do?
Monitor trees early in the growing season to look for signs of infestation. If detected, quickly remove those isolated feeding areas where the mites reside.
Jodi Zirbel is with Epic Creative, Wis. Article provided by Mauget, a leader in micro-injection and micro-infusion tree care. Contact Mauget or visit www.Mauget.com to learn more about Eriophyid mites.