Efficacy of Heterorhabditis baujardi (Rhabditida: Heterorhabditidae) against Rhipicephalus microplus (Acari: Ixodidae) in presence of susceptible and alternate insect hosts.

This study evaluated the influence of alternate insects hosts Mahanarva spectabilis and Galleria mellonella on the efficacy the entomopathogenic nematode, Heterorhabditis baujardi isolate LPP7, for Rhipicephalus microplus control. In the first experiment, engorged R. microplus females were exposed to entomopathogenic nematode H. baujardi LPP7 with or without the presence of M. spectabilis nymphs or G. mellonella larvae. There were also groups containing only M. spectabilis or G. mellonella exposed to H. baujardi and a control group for each arthropod. In the second experiment, engorged females were exposed to different concentrations of H. baujardi which were reared from M. spectabilis and G. mellonella. Mortality rates of engorged R. microplus females, held together with EPN-infected M. spectabilis or G. mellonella inside, was 100% after five days, while the group containing only ticks reached 86%. EPNs caused reduction (p < 0.05) in the amount of eggs produced by engorged females. In the second experiment, the use of nematodes reared in M. spectabilis and G. mellonella also caused a decrease (p < 0.05) in the egg mass weight of R. microplus. The inhibition rate of egg-laying was greater than 80% for all treatments, reaching 92% in the treatment at a concentration of 800 EPNs/female, with nematodes reared in G. mellonella. We can conclude that, under laboratory conditions, the presence of another host did not reduce the activity of H. baujardi on R. microplus. Infective juvenile of entomopathogenic nematodes reared in M. spectabilis or G. mellonella have similar virulence against R. microplus engorged females. [ABSTRACT FROM AUTHOR]