Clover mites (Bryobia praetiosa) are minute, reddish-brown arachnids that feed on plant sap from grasses and clovers. They are classified as nuisance pests because they enter buildings in large numbers, particularly in the spring and fall. They do not bite people, transmit diseases, or damage household furnishings. The primary issue is the red-orange stain they leave when crushed, which is the pigment from their body fluids. Understanding the natural enemies of this pest is important for homeowners seeking to manage outdoor populations and minimize indoor invasions.
Specialized Mite and Insect Predators
The most effective biological control of clover mites comes from other mites and small insects that specifically hunt and consume them. Predatory mites, particularly those in the families Anystidae (whirligig mites) and Phytoseiidae, are the primary microscopic agents of control in the landscape. These specialized hunters are often found in the same dense vegetation that clover mites prefer, exerting consistent pressure on the population.
The whirligig mite, Anystis baccarum, is a notable example, recognized by its rapid, erratic running. While Anystis is a generalist predator of many small arthropods, it is a voracious consumer of pest mites, including the clover mite, and is active across all its life stages. Other mites, including Bdellidae and Cunaxidae, are also documented predators of Bryobia praetiosa in the soil and on plants.
Minute pirate bugs (Orius species) are also significant predators, despite their generalist feeding habits that include thrips and aphids. These true bugs use piercing-sucking mouthparts to consume the body fluids of their prey. Both the nymph and adult stages are known to feed on spider mites and their close relatives, which include clover mites. Larvae of lacewings, often called aphid lions, are also important, as they are non-selective hunters that will readily consume any small, soft-bodied arthropod, including clover mites and their eggs, when encountered on foliage.
Generalist Arthropods and Other Consumers
Beyond the specialized hunters, a wider variety of generalist arthropods contribute to clover mite control as part of their varied diet. Common garden spiders, such as jumping spiders and cobweb weavers, will opportunistically capture and consume clover mites that stumble into their hunting range or webs. Their widespread presence in the landscape means they contribute to background suppression of pest numbers.
Other small, mobile arthropods like harvestmen (daddy longlegs) and various species of ground beetles also feed on clover mites they encounter in the litter layer and on the soil surface. Their feeding is less targeted than the specialized mites but helps to reduce the population of mites moving between the lawn and the foundation of a home. Larger animals, such as certain birds and lizards, may incidentally consume clover mites while foraging, but their impact on localized infestations is minimal compared to the concentrated feeding of micro-predators.
Encouraging Natural Control in the Landscape
Supporting the natural enemies of clover mites is the most sustainable approach to long-term population management. The primary action is avoiding broad-spectrum insecticides, which kill beneficial predators more effectively than the pest mites they are meant to control. Allowing a diversity of plant life in the yard also helps, as it provides pollen and nectar sources that sustain generalist predators like minute pirate bugs and lacewing adults when mite populations are low.
Maintaining a small, vegetation-free barrier, typically 18 to 24 inches wide, around the home’s foundation can reduce the chance of indoor invasions. This barrier forces mites to cross an inhospitable, sun-exposed zone. This is effective since clover mites prefer moist, cool conditions. Ensuring the soil around the foundation is not overly dry, which can be achieved through supplemental watering in exposed areas, discourages mite activity and helps to maintain the habitat preferred by many beneficial soil-dwelling mites.