Entomopathogenic nematodes as control agents of developmental stages of the black-legged tick, Ixodes scapularis

Thirteen species or strains of entomopathogenic nematodes of the genera Steinernema and Heterorhabditis were tested in vitro against unfed and engorged larvae, nymphs, and adults of the black-legged tick, Ixodes scapularis. Nematodes were pathogenic to engorged female ticks, but not to unfed or engorged larvae, nymphs, males, and unfed females. Steinernema riobravis (355) and Heterorhabditis megidis (M145) killed ticks most rapidly, with mean day of death postinfection of 2.5 and 3.5 days, respectively. However, all nematode strains and species were lethal to engorged female ticks within 7.5 days. Development of juveniles and reproduction of nematodes did not occur inside the tick cadavers, because no infective juveniles (IJs) emerged from cadavers after 40 days, and no nematode life-cycle stages other than the primary IJs could be isolated from cadavers. Egg masses were produced by 4 of 702 nematode-infected, engorged females. Egg masses produced were not significantly smaller than masses produced by control ticks; however, only 1 of the 4 egg masses hatched, whereas all of the egg masses produced by the control ticks hatched. Entomopathogenic nematodes may be useful as an alternative management method for I. scapularis populations, and may be more acceptable than acaricidal chemicals for use in infested areas.