and Life History:
Eriophyid mites overwinter as adult females, called a deutogyne. This is a special kind of female mite that is able to go dormant and wait out bad weather and conditions, like winter or extreme heat. Females seek protection in cracks and crevices in the bark, buds or down in leaf litter. Once spring comes and foliage starts to develop, females begin feeding and laying eggs. A female can lay about 80 eggs over a months time producing both male and female mites. Mites hatch and need to pass through two developmental stages. The time of development from egg to adult can take one to two weeks depending on conditions. Mites do not mate with each other; sacs that the male leaves lying around on the leaf surface fertilize the females as she walks around. No wining, dining or song in an Eriophyids lifestyle.
While Eriophyid mites are small, they are mobile and can move around on a plant just fine. However if you are 1/100 of an inch long, how the heck do you get from plant to plant or tree to tree? Eriophyid mites rely on wind, birds, and flying insects to disperse. Eriophyids, along with other arthropods, have been collected blowing in air currents hundreds and hundreds of feet above the ground. For the home landscape, people are also an important mode of transportation for mites. Many introductions into your landscapes are from movement of infected plant material.
Bud mites are specific to infesting the developing buds and fruits of certain plants. Common bud mites found in Whatcom County are the redberry and dryberry mites. Both these mites cause the developing fruit of black berries to be deformed and stunted. Next time you pop a Himalayan blackberry with an undeveloped druplet in your mouth, you probably just ate a world of mites!
Gall mites cause abnormal tissue growth of the plants hairs and leaf cells. The gall forms a pocket that provides a protective area for the small mites to feed and reproduce. These galls can be quite apparent like we see in the Maple bladder gall mite. Galls can also appear as hairy mats called erinea like we see on walnuts infested by the walnut blister mite.
True blister mites cause plant deformations very similar to those of gall mites. The difference is that the pocket is formed in the mesophyll (internal leaf tissue) instead of the outer surfaces of the leaf. Pears in Whatcom County can have infestations of the pear blister mite.
Rust mites are common on apples and pear leaves. Rust mites generally do not cause any extreme deformation of the leaf surface like the other Eriophyid mites. Rust mites feed on the cellular contents of the leaf, which results in a bronzing or silvering effect. Very high populations can cause early defoliation.
Monitoring & Management:
If you dont feel this way, prune off infected leaves and use a dormant oil to smother the overwintering females.
It is only under rare circumstances that a pesticide application is recommended. Eriophyid mites do very little damage to plants and most plants can tolerate huge populations. Apple growers dont even get a little trigger-happy when rust mites build up to over 300 per leaf. In fact, Washington State apple growers enjoy having established populations of rust mites. WSUs own Dr. Stan Hoyt was one of the worlds pioneers in Integrated Pest Management during the 1960s. He found that if growers could tolerate populations of rust mites, spidermites out-breaks happened less frequently. Why? Because rust mites offer a great alternative food source for our friends, the predatory mites. Broad-spectrum insecticides used for controlling codling moth, killed off the predatory mites. This, along with pesticide resistance, caused uncontrollable spidermite out-breaks. Learning this, Dr. Hoyt developed a program to conserve predatory mites by using selective pesticides for codling moth and tolerating rust mite populations. This program allowed predatory mites to build up enough to control spidermite populations as they appeared. Dr. Hoyts efforts paved the way to changing Washington State growers attitudes and contributed to the worldwide adoption of Integrated Pest Management.
So dont be ashamed of your red, pimply maple; this type of tolerance was key to changing pest management practices.
To reach Todd Murray please call (360) 676-6736 or e-mail him at: firstname.lastname@example.org