Bermudagrass & Zoysiagrass Mites
Bermudagrass mite, Aceria (Eriophyes) cynodoniensis, and zoysiagrass mite, Aceria (Eriophyes) zoysiae, are very small mites, measuring approximately 1/100 inch long, and cannot be seen with the naked eye. With magnification, they are worm-like or sausage-like and creamy white. Since they are eriophyid (gall-making) mites, they have only two pairs of legs in both nymphal and adult stages.
Adult mites infest protected tissues of the grass plant (primarily under the leaf sheath). Eggs are deposited in these areas. The life cycle (egg to adult) can be completed in five to seven days and there can be many generations per year. Bermudagrass and zoysiagrass mites are active primarily in late spring and summer.
Bermudagrass is the only known host of bermudagrass mite and zoysiagrass is the only known host of zoysiagrass mite.
Damage from bermudagrass mite may be first noticed in early spring as bermudagrass breaks dormancy, although injury may become more severe later in the growing season. Injured grass has extremely shortened internodes, which produces a typical rosetting and tufted growth, or a witch’s-broom effect. With severe infestations there is almost no green regrowth, and the turf is a mass of large knots which often die, leaving brown areas in the lawn. Infested turf usually thins, allowing weed development. Well-fertilized bermudagrass appears to be more attractive to mites than starved grass, and injury is more pronounced during dry weather when grass is under stress.
Zoysiagrass mite is more damaging to its host than is bermudagrass mite because zoysiagrass is slower growing. The appearance and life history of zoysiagrass mite are similar to bermudagrass mite. Damage occurs once grass breaks dormancy. Infested leaves have pale white or yellow streaks and plants are stunted. The upper leaf surface is “rolled up” and becomes caught within the older twisted leaves, creating an arch which is termed “buggy whipping”.
Inspection & Control
Look for plants with a stunted, rosetted, or tufted appearance. Pull leaf sheaths away from the stems and examine the exposed area with a 10x to 20x hand lens or a dissecting microscope. Look for mites and spherical, transparent eggs.
Most varieties of common bermudagrass (Cynodon dactylon) are highly susceptible to bermudagrass mite damage, but varieties such as “Midiron”, “Tifdwarf”, “Tifgreen”, and “Tifway” with African bermudagrass (Cynodon transvaalensis) parentage are highly resistant to the mite. Of these, “Midiron” is highly recommended for use in Oklahoma and “Tifgreen” and “Tifway” can be used in some areas.
Zoysiagrass varieties differ widely in susceptibility to zoysiagrass mite. The variety “Meyer”, which is widely planted in Oklahoma, is one of the most susceptible to attack by zoysiagrass mite. The varieties “Royal” and “Emerald” are highly resistant, and “El Toro” has intermediate resistance.
Management practices appear to have an important influence upon the severity of mite infestations. Bermudagrass turf that has been “over-seeded” with a winter grass is more severely damaged in spring and early summer than turf that is not over-seeded. Other factors such as the amount of thatch, irrigation, soil fertility, summer temperatures, and shade appear to affect the extent of mite damage at different times during the growing season.
Chemical control measures are not always dependable and repeat applications may be necessary. Treatment combined with nitrogen fertilizer in spring may give both a significant reduction in injury caused by the mites and an increase in the green appearance of the grass. Treatment in fall sometimes gives a distinct reduction in the amount of mite-infested grass the following spring.