Citrus bud mite—Eriophyes sheldoni
Severely deformed blossoms, foliage, or fruit are generally the first clues that this eriophyid mite (family Eriophyidae) is present. It is an occasional pest on lemons any time of year near the coast and less frequently in interior southern areas. It rarely or never is a pest in the Central Valley or desert areas or on citrus varieties in California other than lemons. Note that numerous species of mites can occur on plants.
Citrus bud mites are about 1/100 inch (0.25 mm) long and a magnification of at least 20× is needed to see them. They are carrot or wedge shaped, tapering toward the rear. Adults and nymphs have 4 legs at the front (wider) end near the mouth. Their coloration is pale green, pinkish, or yellowish. The spherical eggs are translucent to whitish.
Where bud mites have previously been a problem, examine the buds at leaf axils on green twigs from midspring through autumn. A leaf axil is the narrow or inside angle where a leaf petiole attaches to a stem and new buds (axillary buds) commonly develop at this location. Dissect some axillary buds and examine them with a 20× hand lens or dissecting binocular microscope with good lighting to estimate the percentage of buds infested with 1 or more live eriophyid mites.
An alternative detection method is to collect axillary buds and place them in a container with 90% ethyl alcohol. Shake this for about 10 seconds so buds are thoroughly coated and any eriophyids are killed and dislodged. At a magnification of at least 20×, examine the fluid for pale, elongate eriophyid mites.
Citrus bud mites develop through 4 life stages: egg, protonymph, deutonymph, and adult. During her life span the adult female lays about 50 eggs mostly in the bud scales of new growth. Eggs are deposited singly or in groups of several. After hatching, nymphs and adults feed protected inside buds or between where a bud and leaf petiole touch. Egg to adult development is about 10 to 15 days when temperatures are warm.
Citrus bud mites are a pest of lemons mostly along the California coast. Their feeding inside the buds kills them and sometimes blackens them. Its feeding causes a rosettelike (bunchy) growth of the subsequent foliage and distortion of flowers and fruit. Fall blooms, and the fruit that develop from them, are most likely to suffer damage.
Treatment thresholds for bud mite has not been established. Even as high as 80% of buds infested with this mite may not cause consistent or predictable damage to the developing fruit.
In gardens and landscapes, predatory mites are believed to help keep bud mites under good control. Black hunter thrips and predaceous mite midges also feed on citrus bud mite. To improve the effectiveness of biological control, control ants, minimize dust (e.g., periodically hose off small trees), and avoid the application of broad-spectrum, persistent insecticides and miticides for all citrus pests. See Protecting Natural Enemies and Pollinators for more suggestions.
Once fruit is set, damage has already occurred and cannot be prevented or corrected. If a reduction in bud mite populations is desired, apply a miticide 2 to 3 months before bloom. Horticultural (narrow-range) oil sprays applied prior to bloom may provide some control of citrus bud mite. Late-fall oil sprays may also help to control the mites.
The most effective products for this mite are only available by hiring a professional applicator. For how to get the services you want, consult Pest Notes: Hiring a Pest Control Company.
For more information see The Citrus Bud Mite, Eriophyes sheldoni Ewing and An Illustrated Guide to Plant Abnormalities Caused by Eriophyid Mites in North America .
Adapted from the publications above and Integrated Pest Management for Citrus, University of California Statewide Integrated Pest Management Program (UC IPM).