Tree Fruit Research & Extension Center

Orchard Pest Management Online

 

Brown mite

Bryobia rubrioculus (Scheuten)

(Acari: Tetranychidae)

-- Elizabeth H. Beers
  (Published online December 2007)

Gallery

Brown mite adult (E. Beers)

This mite species was a well-known pest for most of time tree fruits have been grown in the Pacific Northwest, but has become quite uncommon in the past few decades. A few Washington apple orchards with recurring populations of brown mite were noted in the early 2000s, and it is currently listed as a pest of pear in California. Both the decline and return of brown mite as a pest are likely due to shifts in orchard pesticide programs, but the exact causes are unknown.

In older literature, there is frequent mention of the clover mite, Bryobia praetiosa occurring on tree fruits. This used to be considered a species complex with variations in life history and host plants. B. rubrioculus has been considered a biotype of the complex, which specializes on fruit trees, but work in the mid-1950s declared the forms on tree fruits a separate species (B. arborea a synonym for B. rubrioculus).

 
Hosts

Hosts include all deciduous fruit trees and almonds.

 
Life Stages

Brown mite egg (E. Beers)

Egg: The overwintering eggs are slightly larger than those of the European red mite, but about the same color (dark brick red). Eggs are laid singly.

Brown mite larva (E. Beers)

Brown mite immature (E. Beers)

Immatures: The larva resembles the larva of European red mite to a large degree (reddish color). At this stage, the long front legs which characterize later stages are not apparent.The protonymphs begin to take on a more distinctive appearance, but still lack the long front legs. The deutonymph (final immature stage) resembles the adult in body shape and color, with long front legs.

Adult: The adult female has a characteristic appearance that makes it readily distinguishable from the other common tree fruit tetranychids.The body color is a dull reddish brown with dark orangeish markings, and somewhat flattened. The integument has a striated appearance, with the striations running horizontally across the dorsum. The front legs are very long, over twice the length of the other legs, and extend forward from the body. The eyes are distinct red widely spaced on the cephalothorax.

 
Life History

Brown mite resting on twig (E. Beers, July 2007)

This species overwinters as a diapausing egg, much the same as European red mite; however, the eggs of brown mite hatch up to several weeks earlier than those of European red mite (late delayed dormant). Egg hatch continues through April, peaking at pink. Newly hatched forms feed on buds, and later on leaves. Unlike other tree fruit spider mites, brown mites do not spin webs, and they often leave the leaf surface and congregate on twigs, sometimes molting there. Their feeding is thought to be mostly nocturnal. Summer (non-diapausing) eggs are laid on leaves, twigs and spurs. Females live for 2-3 weeks, and lay about 30 eggs. The spring generation immatures molt primarily on the twigs (>90%), while the first summer generation immatures molt primarily on the leaves. There are three to four generations per year. A summer generation begins in July and females of this generation lay aestivating eggs; by late summer the population is composed primarily of the egg form. These eggs remain in diapause through the winter.

 
Damage

Damage is similar to that caused by other spider mites. All motile stages feed on the leaves and remove chlorophyll. Leaves become stippled from feeding marks, and may become pale or bronzed; however, defoliation is less likely with this species.

 
Monitoring

Monitoring the first generation must take into account this species habits of congregating on the twigs, thus early samples should be consist of buds, and later leaves and twigs. Sampling later generations can be done with leaf samples using the same method as for other tetranychid species.

 
Biological Control

Brown mite has a number of natural enemies, including predaceous mites, lady beetles, anthocorids, and predatory mirids. However, the relative impact of biological control agents is little studied in Pacific Northwest orchards, and they not considered to be very effective.

 
Management

There is no current research on this pest, however, older literature suggests that pink sprays are most effective. Specific miticides which are effective for control of other spider mites should also be effective on brown mite.

 
References Consulted

Anderson, N. H., and C. V. G. Morgan. 1958. Life-histories and habits of the clover mite, Bryobia praetiosa Koch, and the brown mite, B. arborea M. & A., in British Columbia Can. Entomol. 90: 23-42.

Elkins, R. B., R. A. Van Steenwyk, L. G. Varela, C. Pickel, D. Gubler, and C. L. Elmore. 2002. UC IPM pest management guidelines: Pear. University of California Statewide Integrated Pest Management Program.

Jeppson, L. R., H. H. Keiffer, and E. W. Baker. 1975. Mites injurious to economic plants. University of California Press, Berkeley, CA.

Madsen, H. F., and C. V. G. Morgan. 1970. Pome fruit pests and their control. Ann. Rev. Entomol. 15: 295-320.

Madsen, H. F., and J. C. Arrand. 1966. The recognition and biology of orchard insects and mites in British Columbia. Publ. 66-2, British Columbia Department of Agriculture.

Newcomer, E. J. 1966. Insect pests of deciduous fruits in the west. Handbook 306, United States Department of Agriculture, Washington, DC.

 
Gallery

Photo Gallery

 

Orchard Pest Management, is copyrighted by the Washington State Fruit Commission. Soft cover copies are available for purchase.
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