Since the beginning of the twentieth century investigators have documented numerous potential tick biological control agents, including pathogens, parasitoids and predators of ticks (Jenkins, 1964; Mwangi, 1991; Mwangi et al., 1991; Samish & Rehacek, 1999; Kaaya, 2003; Ostfeld et al., 2006). Several authors have reviewed specific groups of natural enemies of ticks, including pathogens (Lipa, 1971; Hoogstraal, 1977; Chandler et al., 2000), nematodes (Samish, Alekseev & Glazer, 2000a, 2000b; Samish & Glazer, 2001), parasitoids (Cole, 1965; Trjapitzin, 1985; Davis, 1986; Mwangi & Kaaya, 1997; Hu, Hyland & Oliver, 1998; Knipling & Steelman, 2000) and predators (Barre et al., 1991; Mwangi, Newson & Kaaya, 1991; Kok & Petney, 1993; Samish & Alexseev, 2001).
In practice, ticks are controlled at present mostly by chemical acaricides (see Chapter 18). However, biological control is becoming an increasingly attractive approach to tick management because of: (1) increasing concerns about environmental safety and human health (e.g. the gradual increase in use of chemical insecticides in several countries is stimulating the growing market of ‘organic’ food); (2) the increasing costs of chemical control; and (3) the increasing resistance of ticks to pesticides. To date, biocontrol has been targeted largely at pests of plants, with only a few efforts to introduce biocontrol agents for the control of ticks. Nevertheless, the knowledge and experience accumulated in plant protection will aid in the development of tick biocontrol methods.