MORPHOLOGICAL CHARACTERISTICS AND INSECT KILLING POTENTIAL OF A SOIL DWELLING NEMATODE, ACROBELOIDES CF. LONGIUTERUS FROM SRI LANKA

Abstract

A free-living nematode was isolated from soils of coastal areas of Northern Sri Lanka using an insect-baiting technique. The morphometrics and the potential of the nematode to control the insect pest, red flour beetle (Tribolium castaneum) and white grubs (Phyllophaga ephilida) were evaluated. The female nematode had a mean body length of 720 µm longer than male (607 µm) with an annulated cuticle and narrow stoma with rhabditoid esophagus. Female with monodelphic, dextral, reflexed with post uterine sac and protuberance vulva at the mid-body, showed sexual dimorphism with male which had a single and reflexed testis. The identification of the nematode was confirmed as Acrobeloides cf. longiuterus (Nematoda: Cephalobidae). The propensity of this nematode to kill insect pests was subsequently tested against T. castaneum and P. ephilida under laboratory conditions. In Petri dish trials, the nematode caused significant mortality of larvae, pupae and adults of T. castaneum within 48 hours. LC50 for larvae ranged from 3.85.9 infective juveniles (IJs)/larva 1.1 and 7.1 IJs/insect for pupae and adults respectively. In soil-based bioassays, the LC50 for T. castaneum larvae was 69.46 IJs/larva, LT50 (Larvae) under the exposure time assay was 4.43 hours, whereas in pot experiment mortality of P. ephilida was recorded 69%. The experimental results showed that A. cf. longiuterus is a potential biocontrol agent and further studies are suggested in this regard.