A nematode, which showed entomopathogenicity, was isolated from Exomala orientalis in Korea, and then identified as Rhabditis blumi. Pathogenicity of R. blumi was evaluated against major cruciferous insect pests, including Artogeia rapae, Mamestra brassicae, and Plutella xylostella. In Petri-dish tests, insect mortality was dose and time dependent, which increased with dose (0–80 dauer juveniles/larva) and time increments. In greenhouse tests, P. xylostella larvae were most susceptible to nematodes, with insect reduction rate of 88.0 %. The rate varied with vegetable species and persistence time of live nematodes on vegetable leaves after spraying. The aeration rate was an important parameter for cultivation of the nematode R. blumi. A sufficient DOT level in the culture using an air-lift bioreactor should be maintained. The nematode growth rate increased with an increasing DOT level and/or bacteria uptake rate. The maximum nematode yield of 1.75 x 105 per ml was obtained under an aeration rate of 6 vvm.

Rhabditis blumi, isolated from Exomala orientalis, is a necromenic type of nematode that possesses several attributes of a potential biological control agent such as ease in culture conditions, high rates of reproduction and virulence, short life cycle and rapid multiplication etc. Pathogenicity of R. blumi was tested against 5 coleopteran species and 5 lepidopteran species. All insect larvae were susceptible to R. blumi, showing over 60% mortality except for Holotrichia kiotoensis and Ectinohoplia rufipes. The highest mortality was observed in Plutella xylostella (88%), followed by Artogeia rapae, Exomala orientalis, Spodoptera litura and Anomala rufocuprea (over 70%). Reproductive capacity of R. blumi differed from each insect species, ranging from 17 to 656 dauer juveniles/mg of insect larva. Dauer juvenile production was most in Plutella xylostella larvae, producing 656 dauer juveniles/mg of host body weight, followed by E. orientalis, H. kiotoensis, and A. rapae larvae (over 100 dauer juvenile per mg).