First report of Steinernema longicaudum and its bacterial symbionts, Xenorhabdus species, in pummelo orchards of Davao region, Philippines

  • Leslie Ubaub University of the South Pacific–Alafua Campus
  • Patricia Stock University of Arizona, Tucson
Keywords: entomopathogenic nematodes, pummelo, Steinernema longicaudum, Xenorhabdus ehlersii, bacterial symbionts


Davao region is the largest pummelo-producing area in the Philippines. Like other tropical fruits, pummelo is infested with several insect pests which consequently lead to the application of synthetic chemicals as deterrent. One potential alternative control measure is the use of soil-dwelling, entomopathogenic nematodes (EPNs), each with its own suite of preferred host, which can be used to control a wide range of insect pests. A survey and soil samples were collected to isolate and identify EPNs in ten pummelo orchards in the Davao region. EPNs were extracted from soil samples using the insect-baiting technique, and were found in only two of the ten sampling areas. EPN isolates were subjected to molecular identification using the 28S ribosomal DNA (rDNA) while its bacterial symbionts were identified using 16S rDNA genes. Both EPN isolates were identified as Steinernema longicaudum. This is the first report of S. longicaudum isolate in the Philippines which can be used as biological control agent against insect pests of pummelo such as citrus rind borer and flower thrips.