Ethanolic extracts of Inula viscosa, Salix alba and Quercus calliprinos, negatively affect the development of the entomopathogenic nematode, Heterorhabditis bacteriophora – A model to compare gastro-intestinal nematodes developmental effect

Heterorhabditis bacteriophora can represent a model system for herbal medication against gastro-intestinal strongylid parasites in determining the recovery and development due to their unique parasitic infectious cycle. The fact that plant extracts impair nematode development is known but their differential impact on stages of the life cycle of H. bacteriophora has never been investigated. We examined the developmental stages resumed from eggs, young juveniles (J_1–3), infective juveniles (IJs), young and adult hermaphrodites of H. bacteriophora upon exposure to crude ethanolic extracts of Inula viscosa, Salix alba, and Quercus calliprinos at concentrations of 600, 1200, and 2400 ppm. Our results showed that plant extracts were highly toxic to the survival of the eggs and young juveniles J₁ to J₃ at all concentrations. The plant extracts inhibited their development and were associated with low reproduction parameters (i.e. fecundity and viability of eggs). The IJs, J₄, young and developed hermaphrodites displayed concentration-dependent negative effect on development with less egg count, poor vulval muscle development, loss of egg laying capacity and progeny development by matricidal hatching. Plant extract of I. viscosa at low (600 ppm) concentration did not impair vulval development. These results suggest that these plant extracts show potential for the control of parasitic rhabditids.