Insect Note #B-4

Prepared by:
Kenneth A. Sorensen, Extension Entomologist

Dated 8/94
Placed on the Web 4/95 by the Department of Entomology, NCSU

Blueberry Bud Mite and Its Control

Acalitus vaccinii (Keifer) Eriophyidae, Prostigmata

The blueberry bud mite, Acalitus vaccinii (Keifer) is an important pest of cultivated blueberries in North Carolina. Early varieties including Wolcott are the usually more severely infested than late varieties.

Appearance

The mite is whitish, elongate and very small. It is about 1/125 of an inch long and, therefore, is invisible to the unaided eye. In the field, rather than examining plants for the mite itself, the presence of the pest is established by looking for the characteristic injury. This injury is most obvious in late April and May.

Habits and Injury

The mite feeds under the bud scales on the developing leaf and floral parts within the blueberry bud. Mites remain almost continuously within the protective confines of the bud for several generations and expose themselves for a short time during migration to new growth in the spring. Plant parts fed upon become roughened and warty in appearance, usually with red discolorations. Persistent feeding by large number of mites results in death of plant tissues and failure of the buds to expand and produce flowers, thereby reducing fruit yield. This injury, though characteristic, often times is confused with winter injury. Ironically, more mite injury results following mild winters.

Control

Control can be obtained with two applications of endosulfan (Thiodan), applications of a 70 second superior type summer oil, or two applications of 0.67 ethion in oil on the young infested buds. Mix 1 quart of endosulfan 25% EC, 2 gallons of oil, or 2 gallons of 0.67 ethion in oil with each 100 gallons of water. One application should be made in July and another application in August. Since the mites are well protected under the bud scales, it is essential that an adequate amount of spray material be applied at a rather high pressure so that proper coverage and penetration occur. Good coverage may require up to 400 gallons per acre of spray, depending on plant size. Approximately 200 pounds of pressure per square inch should be maintained while spraying.

Pruning out old canes also helps reduce bud mite populations.

A fungus parasite, Hirsutella thompsonii, of the blueberry bud mite reduces populations during the summer months. However, climatic conditions from November through May hinder development of the fungus.

The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsements by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. All pesticide recommendations provided in this publication apply to pest control in North Carolina. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain information about product usage in your locale and examine a current product label before applying any chemical. The information presented on pest biology is based on conditions in North Carolina and may not be applicable to your locale. For further information, we recommend that you contact the Cooperative Extension Service office in your county.