Peach Silver Mite, Aculus cornutus (Banks)

I. Introduction: The peach silver mite (PSM) is a member of the rust mite family, with a worldwide distribution, that was first described from peach in Washington, D.C. in 1905.

II. Hosts: Peach, nectarine, and almond.

III. Description: Full grown PSM are light amber to yellow, wedge-shaped, and about 7/1000 inch (0.2 mm) in length.

IV. Biology: Females overwinter on the tree in the buds and bud scales as specialized hibernating forms called deutogynes, which are incapable of reproducing during the season they are formed. Early in the spring, mites will invade the tender growing tips to feed. Feeding and reproduction, resulting in numerous generations, occurs on the leaf surface until hibernating females are again produced in the fall.

V. Injury: PSM cause two types of injury to foliage depending upon the age of the leaf upon which feeding occurs. Mite feeding on young leaves results in injury referred to as "yellow spot", which is characterized by yellow spotting and chlorosis along the veins, with an upward longitudinal folding of the leaf margin. The spots are circular and may be pinpoint to more than 1/16 inch (1.5 mm) in diameter. In severe infestations, spots coalesce resulting in leaves with a mottled appearance. Prolonged summer feeding on mature leaves results in a silvery or reflective appearance that develops late in the season just before leaf drop. This injury has been reported to reduce fruit size and cause premature fruit drop.

VI. Monitoring: With the aid of a hand lens, begin inspecting leaves for PSM at bud break and continue throughout the summer. There is no validated threshold available for PSM, however, populations less than 200/leaf can probably be tolerated under most conditions without economic impact. A low to moderate population is considered advantageous to provide an alternative food source for mite predators when primary prey species may be scarce.

This is taken primarily from a chapter by H. W. Hogmire and D. F. Polk on peach indirect pests, reprinted with permission from Mid-Atlantic Orchard Monitoring Guide, published by NRAES, 152 Riley-Robb Hall, Ithaca, New York 14853-5701. (607) 255-7654.
Back to Virginia Peach page
Back to Virginia Fruit Page