Banks grass mite,
Banks grass mites are common in Colorado and can be destructive pests of turfgrass. These mites are very small and light in color. Banks grass mites are paler in younger life stages but green for most of the season. Sometimes these mites turn bright red when food is scarce. Unlike some spider mites, the Banks grass mite does not have elongated forelegs.
• The Banks grass mite is a pest of turfgrass in Colorado. It is also considered an agricultural pest.
• Drought stressed turfgrass is highly susceptible to mite feeding injury. Chemical control is usually not warranted in healthy turfgrass.
• Banks grass mites are a species of spider mite. All spider mites are in the family Tetranychidae and produce webbing.
Banks grass mite adult. The Banks grass mite is destructive to turf and is also a pest of wheat and corn grown in Colorado. Drought-stressed turfgrass is the most susceptible, therefore it is encouraged to keep grass adequately watered year-round. Image credit: F.C. Schweissing, Bugwood.org
Banks grass mite adults dispersing from the tip of a grass blade. Image credit: Whitney Cranshaw, Colorado State University, Bugwood.org
Life history and habits
Banks grass mites overwinter as adults in soil, dead leaves, and weeds. These mites are most active in late spring through summer. Cream-colored eggs are laid in clusters on stems and leaves. Banks grass mites can produce multiple, overlapping generations each growing season. A protective webbing of silk is produced when populations are high.
Banks grass mite feeding causes chlorotic spots to form on leaves and may cause the entire leaf to die back if feeding is continuous. The early stage of feeding injury is characterized by stippling, and sometimes slight purpling of the injured grass blade. Severe injury can progress rapidly and is almost always related to drought stress. When grass is dead, it becomes stiff and brown to yellow in color.
The underside of leaves should be inspected near the base of the plant, with extra attention given to leaves with symptoms of feeding injury. Look for the presence of webbing and the presence of mites, which appear as small moving dots. Shaking foliage over a white piece of paper will dislodge mites from the host plant and make them easier to spot.
Problems due to Banks grass mite are often avoided when plants are adequately watered. Adequate watering is encouraged year-round since control of Banks grass mite is often ineffective under drought conditions.
There are many natural enemies of the Banks grass mite including predatory mites, thrips, and pirate bugs. Therefore, when chemical control is warranted, broad-spectrum pesticides should be avoided to help protect natural enemies.
Chemical control is often unnecessary in healthy turf. Please consult the Utah State University factsheet for recommendations on chemical management of Banks grass mite.
Brewer, M., 1995. Banks Grass Mite: Oligonychus pratensis. University of Wyoming: Department of Renewable Resources. Available https://wyoextension.org/parkcounty/wp-content/uploads/2016/03/Banks-Grass-Mite.pdf
Cranshaw, W. 2013. Clover and Other Mites of Turfgrass. Colorado State University – Extension. Available https://extension.colostate.edu/topic-areas/insects/clover-and-other-mites-of-turfgrass-5-505/
Texas A&M University (n.d.). Insect Pests of Sorghum. Texas A&M Agrilife Extension. Available https://agrilife.org/sorghumipm/insect-pests/banks-grass-mite/
Utah State University. (n.d.). Bank’s Grass Mite: Oligonychus pratensis. Utah State University: Extension. Available https://extension.usu.edu/pests/ipm/turf-pest-guide/ar_banks-grass-mite