Effects of tannin-rich host plants on the infection and establishment of the entomopathogenic nematode Heterorhabditis bacteriophora Itamar Glazer a,⇑ , Liora Salame a , Levana Dvash b , Hussein Muklada b , Hassan Azaizeh c,d , Raghda Mreny c , Alex Markovics e , SergeYan Landau b a Department of Entomology and Nematology, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel b Department of Natural Resources, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250, Israel c The Institute of Applied Research (Affiliated with University of Haifa), The Galilee Society, Shefa-Amr 20200, Israel d Tel-Hai College, Upper Galilee 12208, Israel e Kimron Veterinary Institutes, P.O.B. 12, Bet-Dagan 50250, Israel article info Article history: Received 3 December 2014 Revised 5 February 2015 Accepted 9 February 2015 Available online 29 April 2015 Keywords: Heterorhabditis bacteriophora Spodoptera littoralis Exsheathment Tannins Recovery Parasitic establishment abstract Parasitized animals can self-medicate. As ingested plant phenolics, mainly tannins, reduce strongyle nematode infections in mammalian herbivores. We investigated the effect of plant extracts known to be anthelmintic in vertebrate herbivores on the recovery of the parasitic entomopathogenic nematode Heterorhabditis bacteriophora infecting African cotton leafworm (Spodoptera littoralis). Nematode infective juveniles (IJs) were exposed to 0, 300, 900, 1200, 2400 ppm of Pistacia lentiscus L. (lentisk), Inula viscosa L. (strong-smelling inula), Quercus calliprinos Decne. (common oak) and Ceratonia siliqua L. (carob) extracts on growth medium (in vitro assay). In control treatments, 50–80% of IJs resumed development to J 4 , young and developed adult hermaphrodites, whereas all extracts, except for C. siliqua at 300 ppm, impaired IJ exsheathment and development. The highest concentration of I. viscosa extract (2400 ppm) had the strongest effect, killing 95% of exposed nematodes. Surviving nematodes did not recover, remaining at the IJ stage. Over the whole cycle, I. viscosa extract inhibited recovery to 25% or less, and did not allow full development to adulthood, whereas 65% of IJs in the control treatment recovered and resumed development, 12% reaching complete maturation within 72 h of incubation. When herbiv- orous S. littoralis larvae were fed with different plant extracts in vivo, I. viscosa had the strongest effect at concentrations above 300 ppm, with 90% of insect-invading IJs not developing to parasitic stages, whereas in the control treatment, 85% of IJs resumed development. Exposure to C. siliqua extract also inhibited exsheathment and development of 75% of the IJs. Half of those that resumed development reached full maturation. P. lentiscus and Q. calliprinos extracts also inhibited development of 50% IJs. Our results suggest that H. bacteriophora can be used to study herbal medication against parasites in animals. Ó 2015 Elsevier Inc. All rights reserved. 1. Introduction Parasitic nematodes of invertebrates, animals, humans and plants thrive and reproduce in their hosts, but they also spend a substantial portion of their life cycle outside the host. To cope with different environmental conditions, these parasitic nematodes have a developmentally arrested stage, the infective juvenile (IJ), which is adapted to withstand the unfavorable conditions outside the host (Sommerville and Davey, 2002). This stage is further equipped with mechanisms for allocating, and establishing in, new hosts (Glazer, 2002). A similar life cycle exists in the gastrointestinal trichostrongylid parasites of ruminants (Chiejina, 1986). The eggs of these parasites are excreted in the animal’s feces and hatch under suitable environmental conditions, producing two nonparasitic lar- val stages followed by an infective L 3 that is ensheathed, i.e., retains the shed cuticle from the previous molt, for protection. When infec- tive trichostrongylid larvae are ingested by the host, they exsheath and, depending on the species, enter either the gastric glands of the abomasum or the crypts of the small intestine, where they molt, return to the lumen, and after a fourth molting, become egg-pro- ducing adults. The ability of parasitized animals to self-medicate seems to be ubiquitous in the animal kingdom (Villalba and Landau, 2012): for example, chimpanzees suffering from parasite-related diseases consume the bitter pith of the plant Vernonia amygdalina (Huffman http://dx.doi.org/10.1016/j.jip.2015.02.002 0022-2011/Ó 2015 Elsevier Inc. All rights reserved. ⇑ Corresponding author. Tel.: +972 50 6220290; fax: +972 3 9604835. E-mail address: glazerit@agri.gov.il (I. Glazer). Journal of Invertebrate Pathology 128 (2015) 31–36 Contents lists available at ScienceDirect Journal of Invertebrate Pathology journal homepage: www.elsevier.com/locate/jip