Grass mites are minute, eight-legged arachnids, meaning they are related to spiders and ticks, not insects. These pests cause significant damage to turfgrass by feeding on the plant’s cell contents, which can quickly lead to widespread lawn discoloration. Infestations are often linked to environmental stress, particularly drought conditions, which weaken the grass and allow mite populations to flourish. Because of their microscopic size, grass mites are frequently overlooked, with their damage often misidentified as a disease or simple lack of water. Understanding these tiny turf enemies is the first step toward effective identification and control.
Defining Characteristics and Main Types
Grass mites are generally less than one millimeter in length, making them extremely difficult to see without magnification. They possess four pairs of legs in their adult stage. They feed by piercing the grass cells and sucking out the contents, a process that causes the characteristic visual damage seen in an infested lawn.
Two of the most frequently encountered types are the Banks Grass Mite and the Clover Mite. The Banks Grass Mite (Oligonychus pratensis) is typically yellowish-green, turning bright orange-red when food becomes scarce. This species thrives in hot, dry weather and causes rapid turf decline.
The Clover Mite (Bryobia praetiosa) is reddish-brown to dark green and has a notably long pair of front legs. Unlike the Banks Mite, the Clover Mite is a cool-season pest, peaking in the early spring and late fall. While they damage turf, they are often recognized as a nuisance pest, migrating into homes and leaving a reddish stain when crushed.
How to Spot an Active Infestation
Mite feeding causes a type of damage known as stippling, which appears as tiny yellow or white spots on the grass blades. This occurs as the mites remove the chlorophyll-containing cells from the plant tissue.
As feeding continues, the turf takes on a sickly, bleached straw color, often progressing to a bronzed or brownish appearance. This damage is concentrated in areas that are warmest and driest, such as south-facing slopes or turf adjacent to sidewalks and driveways.
A simple field test can confirm their presence. Place a sheet of white paper on the ground in the affected area, then forcefully sweep the grass blades across the surface. If mites are present, you will see tiny, moving specks that may leave a reddish streak when smeared, confirming an active infestation.
The Mite Life Cycle and Seasonal Activity
The grass mite life cycle includes four stages: egg, larva, nymph, and adult. This cycle can be completed in as little as seven to fifteen days under favorable conditions. This rapid turnover allows populations to multiply exponentially, leading to multiple generations within a single growing season.
Seasonal activity is determined by the species and environmental conditions. Banks Grass Mites are most active during the warmest parts of the year, flourishing in the heat and drought stress of mid-summer. Conversely, Clover Mites are cold-tolerant and are most active in the spring and fall when temperatures are cooler.
Overwintering occurs in the adult or egg stage, often in the soil or at the base of the grass plant. Targeting the active stages with a treatment is necessary, but the presence of eggs requires multiple applications to break the cycle.
Effective Management and Control Strategies
Successful grass mite management relies on a combined approach of cultural practices and, when necessary, targeted chemical treatments. Since mite populations are strongly associated with drought stress, ensuring the turf receives adequate and consistent water is a primary preventative measure. Proper irrigation helps the grass recover quickly from feeding damage and makes the plant less susceptible to infestation.
Cultural practices also involve maintaining proper turf health through appropriate fertilization and mowing height, which promote vigor and air circulation. For Clover Mites specifically, hosing down the sides of buildings or structures where they congregate can disrupt their migration indoors. Removing damaged turf material may also be necessary to encourage new, healthy growth.
When the infestation is severe, chemical control using specialized products called acaricides or miticides is required. General-purpose insecticides are often ineffective against mites, and some can worsen a mite problem by eliminating their natural predators. The active ingredients bifenthrin or lambda-cyhalothrin are commonly used for control, though specific miticides like those containing neem oil or insecticidal soap offer less toxic alternatives. Multiple applications, spaced according to label directions, are necessary to ensure that newly hatched mites are also targeted and the entire life cycle is interrupted.