Environmental Entomology, 49(2), 2020, 412–421 doi: 10.1093/ee/nvaa014 Advance Access Publication Date: 10 March 2020 Insect-Microbial Interaction Research Entomopathogenic Nematodes as Potential Biological Control Agents of Subterranean Termite, Microcerotermes diversus (Blattodea: Termitidae) in Iraq Jawad B. Al-Zaidawi,1 Javad Karimi,1,3, and Esmat Mahdikhani Moghadam2 Downloaded from https://academic.oup.com/ee/article-abstract/49/2/412/5802319 by guest on 15 April 2020 1Biocontrol and Insect Pathology Lab., Department of Plant Protection, Ferdowsi University of Mashhad, Mashhad, Iran, 2Department of Plant Protection, Ferdowsi University of Mashhad, Mashhad, Iran and 3Corresponding author, email: [email protected] Subject editor: Angel Acebes-Doria applyparastyle "fig//caption/p[1]" parastyle "FigCapt" Received 5 September 2019; Editorial decision 5 February 2020 applyparastyle "fig" parastyle "Figure" 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 NList_dot_numeric2=HeadC=NList_dot_numeric=HeadC efficacy of these strains were evaluated to test the feasibility of indigenous EPNs to be used in a biological control NList_dot_numeric3=HeadC=NList_dot_numeric1=HeadC program. The biological traits examined included pathogenicity, penetration, and reproduction of EPN species. NList_dot_numeric2=HeadD=NList_dot_numeric=HeadD Filter paper and wood bioassays were conducted using six concentrations: 25, 50, 100, 200, 400, and 600 IJs/termite. NList_dot_numeric3=HeadD=NList_dot_numeric1=HeadD In both tests, all strains were virulent against M. diversus workers. The LC of S. carpocapsae in both petri dishes NList_dot_numeric2=HeadE=NList_dot_numeric=HeadE 50 and in containers with sawdust was (57.9 and 15.7 IJs/termite) less than both indigenous (274.2 and 60.8 IJs/termite) NList_dot_numeric3=HeadE=NList_dot_numeric1=HeadE 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 ofM. diversus workers. Key words: Entomopathogenic nematode, Heterorhabditis bacteriophora, Microcerotermes diversus, Biological control One of the most common social insects documented in many coun- to manage subterranean termites in Iraq mainly includes application tries around the world are termites, which are reported as economic of chemical pesticide (Al-Jassany 1996). The main insecticide fre- and destructive pests, especially in Iraq. Some species of termite at- quently used in the country to control this subterranean termite is tack wood sources above the soil surface, while others cause damage Chlorpyrifos 48% TC. Estimates of the cost to import Chlorpyrifos to trees or crops underneath the soil (Josens 1983). The most eco- in 1998 and Fipronil in 2001 into Iraq were 1.1 and 2 million USD, nomically important termite species in agricultural areas of Iraq is respectively (Al-Zubaidy and Al-Jassany 2013). The ingredients of Microcerotermes diversus (Silvestri) (Blattodea: Termitidae). This these compounds have adverse environmental effects. For example, species can attack fruit trees and agricultural crops in various re- the use of high concentrations of chemical pesticides for a long time gions, as well as buildings causing massive property damage. could contaminate the crops and may cause a serious problem to Furthermore, the termite tunnel on stem trees causes weakness to the human and their agro-ecosystem (Rola and Pingali 1993, Potter and stems by consuming the carbohydrate ultimately causing collapse of Hillery 2001). Another method conducted to control the termites trees (Al-Jassany 1996). in Iraq was commercial formulation of fungi Metarhizium aniso- Currently, several control approaches are applied against this pliae which was used effectively to protect olive trees against termite costly pest, including cultural, botanical, and chemical controls. Of species such as M. diversus (Hussain et al. 2011, Al-Zubaidy and these methods, chemical control involves the use of synthetic insecti- Al-Jassany 2013). Because of concerns about the side effects of pro- cides such as bifenthrin, fipronil, cypermethrin, and deltamethrin longed pesticide application and positive results of using biocontrol (Wagner et al. 2003). Currently, the most common method applied agents, it is crucial to reduce these applications by finding alternative © The Author(s) 2020. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: [email protected]. 412 Environmental Entomology, 2020, Vol. 49, No. 2 413 approaches to control subterranean termites, including the use of they were allowed to warm up to room temperature (25 ± 1°C) for entomopathogenic nematodes (EPN) (Gouge 2005). The cryptic 2 h. Also, their viability for motion was checked using dissected habitat of subterranean termite nesting and foraging primarily in microscope. the soil provides suitable conditions for application of EPNs (Epsky and Capinera 1993). Collection and Maintenance of Termites The families Steinernematidae and Heterorhabditidae (Poinar The termite species (M. diversus) were collected from infested trees 1990) are widely available commercially and have been used com- in citrus and palm orchards in central Baghdad. The termite colony monly to control a number of different soil insect pests (Kaya and used in this study was transferred to laboratory and maintained in Gaugler 1993, Kaya et al. 2006). These are obligate lethal parasitic plastic containers (80 × 70 × 70 cm) with pieces of wood in a dark pathogens of insect pests. The ‘infective juveniles (IJs) of the nema- chamber at 25 ± 1°C and 65–70% relative humidity. For the experi- todes’ live symbiotically with bacteria of the genera Xenorhabdus ment, a modified aspirator was used to collect the termite workers and Photorhabdus, respectively (Poinar 1990, Ciche et al. 2003). from the colony. The nematodes can enter the target insect pest through natural openings such as mouth, anus, and sometimes via the cuticle causing Downloaded from https://academic.oup.com/ee/article-abstract/49/2/412/5802319 by guest on 15 April 2020 Laboratory Bioassay mortality of pests (Grewal et al. 2005). The EPNs are widely distrib- EPNs’ Efficacy, Reproduction, and Penetration in G. mellonella uted in soils throughout the world (Kaya 1990). Moist, cool, and Three isolates of EPN were used in the experiments. The applied dark conditions of termite’s habitat are ideal conditions for the sur- isolates were commercial strains of S. carpocapsae (Capsanem) and vival and movement of Steinernematid and Heterorhabditid nema- H. bacteriophora (Larvanem) supplied by Koppert B.V. (Berkel en todes (Lewis et al. 1992; Kaya and Gaugler 1993, 1997; Glazer et al. Rodenrijs, the Netherlands) and H. bacteriophora IRQ.1 strain 2001). Preliminary studies have indicated that some termites are sus- (Al-Zaidawi et al. 2019). All strains were reared under laboratory ceptible to Steinernema species (Chouvenc et al. 2011). Indigenous conditions with IJs being collected. The bioassay was conducted to natural enemies are highly recommended and important to save the determine the lethal concentration of EPNs against last instar larvae time of adoption and importation of new species as well as to avoid of G. mellonella under laboratory conditions. Five concentrations possible side effects on nontarget species. For example, native EPNs of EPNs (100, 200, 400, 600, and 800 IJs/larva) were inoculated in isolated from Iran have been used effectively against fruit fly Dacus Petri dishes (9 cm in diameter) with wetted filter papers. Four rep- ciliates Loew (Diptera: Tephritidae) which was the most serious pest licates (10 larvae) per treatment (concentration) and untreated con- of cucumber, melon, musk melon, and other related fruits (Kamali trol were used in this bioassay. Each replicate received 1 ml of EPNs et al. 2013). Although applying nematodes against various insect suspension. Larvae mortality was recorded 48 h postinfection. Half pests all over the world is considered as a safe and successful control of the infected larvae were dissected under a stereomicroscope after method, the use of biological control agents against termites is still rinsing with distilled water. Next, the number of IJs found per larva very limited and more research is required to establish which biocon- was counted to evaluate the penetration of each EPN species. The trol agent is effective under which conditions (Yu 2009). other half of the infected larvae