Boxwood spider mite

The boxwood spider mite, Eurytetranychus buxi, becomes active in late April, early May in Oregon. The mites overwinter in the egg stage.

Description:
These mites are generally tan, sometimes reddish-colored, with two large dark patches on either side of their body. They are slightly smaller than two-spotted spider mites. Adult females are round and robust compared to the smaller, wedge-shaped males which often project two pair of legs forward and two pair of legs backword. Eggs are yellowish-orange and generally found on the underside of the leaves.

Damage
Boxwood spider mite feeding causes fleck-like scratches on the upper leaf surface. Generally there is no webbing associated with this mite.

Monitoring:
Look for yellowing and flecking on leaves. Closer inspection, particularly under the leaves, may reveal spider mites, cast skins, or eggs.

Management
Cultural control: Japanese boxwood is reputed to be less suceptible.

Biological control: In Maryland, researchers assessing abundance of natural enemies on landscape plants found 20 taxa of benefical arthropods on boxwood including green lacewings, lady beetles, harvestmen, and spiders (Stewart et al. 2002). Spiders were the most abundant predator (70.6% of all predators). Mites reared on imidacloprid-treated boxwood was extremely toxic to two predators, Chrysoperla rufilabris and Stethorus punctillum (Creary, 2009).

Chemical control: Dormant oils, particularly aimed at the underside of the leaves, target overwintering mites. Light summer oils and insecticidal soaps are low toxicity materials that may be applied to manage these mites. Good contact is necessary. One trial in Belgium evaluating control of boxwood spider mite eggs showed that all acaricides they evaluated (the list included acaricides with EPA registrations including: clofentezine, fenbutatin oxide, hexythiazox, and pyridaben) controlled 50- 100% of developing winter eggs when applied in April. A mixed population of winter and summer eggs was most effectively controlled with hexythiazox followed by clofentrozine (Hellmans and Goossens, 2000). Boxwood plants treated with imidacloprid has been linked to increased fecundity of boxwood spider mite on those treated plants (Szczepaniec and Raupp, 2013). Check the PNW Insect Management Handbook for additional chemical control options.

 

References

Creary, S. 2009. Indirect effects of imidicloprid on natural enemies of spider mites in two systems. University of Maryland. Master's Thesis.

Hellmans, A. and F. Goossens. 2000. Control of box spider mite (Eurytetranychus buxi). Verbondsnieuws 2000 Vol. 44 No. 15 pp. 27-29.

Steward, C., K. Braman, and B. Sparks. 2002. Abundance of beneficial arthropods on woody landscape plants at professionally-managed landscape sites. J. Environ. Hort. 20(2):67–72. June 2002

Szczepaniec, R. and M. Raupp. 2013. Direct and indirect effects of imidacloprid on fecundity and abundance of Eurytetranychus buxi (Acari: Tetranychidae) on boxwoods. Exp. App. Acar. March 2013. Vol 59 (3) pp307-318.

Useful links.

Russel, H. 2013. Boxwood Insect Pests Michigan State University Extension

Boxwood spider mite. North Carolina State University.

Boxwood Spider mite. Pests of Trees and Shrubs. IPM in Mid-West Landscapes.

Original publication: 5/1/2009
Most recent update. 4/19/2016

Author: R.L. Rosetta, Extension Nursery Integrated Pest Management, Department of Horticulture, Oregon State University