SoutheaSt aSian J trop Med public health 18 Vol 48 No. 1 January 2017 Correspondence: Apichat Vitta, Department of Microbiology and Parasitology, Faculty of Medical Science, Naresuan University, Phitsa- nulok 65000, Thailand. Tel: +66 (0) 55 964653; Fax: +66 (0) 55 964770 E-mail: apichatv@nu.ac.th PRELIMINARY SURVEY OF ENTOMOPATHOGENIC NEMATODES IN UPPER NORTHERN THAILAND Apichat Vitta 1,2,3 , Chamaiporn Fukruksa 1 , Thatcha Yimthin 1 , Kitsakorn Deelue 1 , Chutima Sarai 1 , Raxsina Polseela 1,2,3 and Aunchalee Thanwisai 1,2,3 1 Department of Microbiology and Parasitology, 2 Center of Excellence in Medical Biotechnology (CEMB), Faculty of Medical Science, Naresuan University; 3 Center of Excellent for Biodiversity, Faculty of Sciences, Naresuan University, Phitsanulok, Thailand Abstract. Entomopathogenic nematodes (EPNs) of the genera Steinernema and Heterorhabditis are used as biocontrol agents for insect pests. Survey of indigenous EPNs provides not only the diversity aspects but also the contribution in pest management in local areas. The objective of this study was to survey EPNs in upper northern Thailand. Nine hundred seventy soil samples were obtained from 194 sites in upper northern region of Thailand; of these 60 (6.2%) had EPNs in 2 genera: Steinernema (32 isolates) and Heterorhabditis (28 isolates). Most EPNs were isolated from loam with a soil temperature of 24-38°C, a pH of 1.5-7.0 and a soil moisture content of 0.5-6.8%. Molecular identifcation based on sequencing of a partial region of an internal transcribed spacer was performed for Heterorhabditis and the 28S rDNA for Steinernema. A BLASTN search of known sequence EPNs revealed 24 isolates of S. websteri and one isolate of S. scarabaei were identifed; closely related to S. websteri (accession no. JF503100) and S. scarabaei (accession no. AY172023). The Heterorhabditis species identifed were: H. indica (11 isolates), H. gerrardi (2 isolates) and Heterorhabditis sp (8 isolates). Phylogenetic analysis revealed 11 isolates of Heterorhabditis were related to H. indica; 2 isolates were re- lated to Heterorhabditis gerrardi and 8 isolates were closely related to Heterorhabditis sp SGmg3. The study results show the genetic diversity of EPNs and describe a new observation of S. scarabaei and H. gerrardi in Thailand. This fnding is new and provides important information for further study on using native EPNs in biological control. Keywords: Steinernema, Heterorhabditis, entomopathogenic nematodes, phylogeny orhabditis are found in diverse geographi- cal regions except Antarctica (Hominick, 2002). Steinernema is symbiotically associ- ated with Xenorhabdus bacteria and Het- erorhabditis with Photorhabdus (Boemare, 2002). EPNs have been used as biologi- cal control agents for insect pests since they have symbiotic bacteria that can kill parasitised insects within 48 hours (Smart, 1995; Denno et al, 2008). EPNs have been INTRODUCTION Entomopathogenic nematodes or EPNs of the genera Steinernema and Heter-