Entomopathogenic Nematodes as Potential Biological Control Agents of Subterranean Termite, Microcerotermes diversus (Blattodea: Termitidae) in Iraq

Abstract

Abstract The infectivity of three species of entomopathogenic nematodes (EPNs) such as Steinernema carpocapsae Weiser (Rhabditida: Steinernematidae), Heterorhabditis bacteriophora Poinar (Rhabditida: Heterorhabditidae), and H. bacteriophora Poinar (IRQ.1 strain) were examined against subterranean termite Microcerotermes diversus (Silvestri) (Blattodea: Termitidae) that is the most economically destructive termite in Iraq. Laboratory and field efficacy of these strains were evaluated to test the feasibility of indigenous EPNs to be used in a biological control program. The biological traits examined included pathogenicity, penetration, and reproduction of EPN species. Filter paper and wood bioassays were conducted using six concentrations: 25, 50, 100, 200, 400, and 600 IJs/termite. In both tests, all strains were virulent against M. diversus workers. The LC50 of S. carpocapsae in both petri dishes and in containers with sawdust was (57.9 and 15.7 IJs/termite) less than both indigenous (274.2 and 60.8 IJs/termite) and commercial (139.6 and 52.6 IJs/termite) Heterorhabditis bacteriophora, respectively. In the field, the percent mortality of the tested workers ranged from 22.5–80 ± 8.3%, 37.5–96.2 ± 8.9%, and 28.7–67.5 ± 6.8% for commercial H. bacteriophora and S. carpocapsae and native H. bacteriophora, respectively. All EPN strains successfully penetrated the M. diversus workers under field conditions, while the results showed that there was a significant difference between the three EPN strains. The percent mortality caused by native H. bacteriophora against termites was higher (43.6 ± 2.7%) than both commercial strains of S. carpocapsae (36.9 ± 1.6%) and H. bacteriophora (29.9 ± 1.4 %). These results highlight the efficiency of EPNs for the control of M. diversus workers.