As a result of increasing concerns regarding environmental safety, increasing costs of chemical controls, and potential resistance of ticks to pesticides, biological controls are becoming a sought-after strategy for tick population management. The use of biological controls for tick management is relatively new and is primarily in its research phase. A number of predators, parasites, and pathogens are currently being evaluated for their potential as effective tick biological controls.
Ticks have a variety of natural predators including ants, spiders, and birds, though most are generalists that only occasionally feed on ticks. As such, these generalist predators tend to be ineffective at significantly reducing tick populations. Guinea fowl and chickens are commonly promoted as tick controls, though research indicates that their tick consumption is minimal and is not effective in reducing local tick populations. Additionally, as guinea fowl wander around a property they can become hosts to ticks themselves, further reducing their value as a biological control. An increase in wild turkey populations has led to questions regarding their impact on tick numbers. Though turkeys will consume ticks on occasion, turkey foraging has not been found to reduce tick abundance and they too can become hosts to a number of tick species.
Research and limited releases of a tiny parasitic wasp (Ixodiphagus hookeri) have shown some minor potential for reduction of deer tick populations. Unfortunately, this wasp requires extremely high tick densities to persist, limiting its usefulness as a biological control in most settings. Nematodes, a type of tiny roundworm, are also being examined as a potential tick control, though they may be too sensitive to colder temperatures to be effective in Maine.
The use of pathogenic fungi is perhaps the most promising biological control for ticks. These fungi penetrate the tick’s cuticle, or outer covering, move into the body, and ultimately kill both nymphal and adult stages of the tick. Commercial products containing these fungi are available for both granular and spray applications. The fungus Metarhizium anisopliae is registered in Maine for tick control.