Lethal and sublethal effects of Iranian isolates of Steinernema feltiae and Heterorhabditis bacteriophora on the Colorado potato beetle, Leptinotarsa decemlineata

Abstract

To determine the LC 50 values of two entomopathogenic nematodes against Leptinotarsa decemlineata Say (Coleoptera: Chrysomelidae) prepupae, different concentrations of the nematodes were tested in soil. Because of the different temperature requirements of the two nematode species, bioassay experiments were conducted at 20 ± 1°C and 27 ± 2°C for Steinernema feltiae Filipjev (Rhabditida: Steinernematidae) and Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae), respectively. Both the isolates were effective against L. decemlineata. LC 50 values of H. bacteriophora against progeny of field-collected adults and laboratory-reared adults were estimated as 8.5 and 7.6 IJ per prepupa, respectively. For S. feltiae the value was calculated as 51.2 IJ per prepupa against offspring of laboratory-reared adults of L. decemlineata only. Cellular encapsulation of both nematode species was observed. Sublethal nematode concentrations caused wing deformation and delayed metamorphosis which may affect Colorado potato beetle adult fitness.

Effect of an entomopathogenic nematode,Steinernema carpocapsaeon haemocyte profile and phenoloxidase activity of the Colorado potato beetle,Leptinotarsa decemlineata

“…Cellular encapsulation of the EPNs has been reported in CPB (Armer et al, 2004;Ebrahimi, Niknam, & Dunphy, 2011;Ebrahimi, Niknam, & Lewis, 2011;Thurston et al, 1994) and, in part may decrease THC. Plasmatocytes and granulocytes are the main haemocytes involved in encapsulation response of the insects against EPNs.…”

“…PO activation in nematode-injected CPB larvae is expected since cellular encapsulation and capsule melanisation are common responses of CPB against EPNs (Armer et al, 2004;Ebrahimi, Niknam, & Dunphy, 2011;Ebrahimi, Niknam, & Lewis, 2011;Thurston et al, 1994).…”

“…Cellular encapsulation of EPNs as an immune response of different insect species has been well documented and different interactions of the bacterial, nematode and host genotypes are responsible for variable efficacy of this immune reaction (Li, Cowles, Cowles, Gaugler, & CoxFoster, 2007;Walter, Dunphy, & Mandato, 2008;Wang, Campbell, & Gaugler, 1995;Wang, Gaugler, & Cui, 1994). CPB larvae also have efficient immune responses against EPNs in which melanisation and cellular encapsulation are described (Armer, Rao, & Berry, 2004;Ebrahimi, Niknam, & Dunphy, 2011;Ebrahimi, Niknam, & Lewis, 2011;Thurston, Yule, & Dunphy, 1994). Prophenoloxidases (proPO) are the inactive form of phenoloxidases (PO) and are synthesised primarily by haemocytes, then released into plasma by cell lysis (Kanost & Gorman, 2008).…”

“…Offspring of the beetles were used for establishing the greenhouse colony (Ebrahimi, Niknam, & Lewis, 2011). In all experiments, three-day-old fourth instar larvae were used.…”

Nematode Pathogenesis of Insects and Other Pests

“…In 2000 Saffari, Madadi, and Karimi (2013) In another study, Ebrahimi, Niknam, and Lewis (2011) assessed the lethal and sub-lethal effects of two isolates of S. feltiae and H. bacteriophora against the prepupae of CPB in soil at two different temperatures. Their results revealed that both isolates were effective against L. decemlineata although H. bacteriophora was more effective at lower concentrations than S. feltiae.…”