The yellow spotless ladybug (YSL), Illeis koebelei is a kind of aboriginal ladybug in Korea. YSL feed on the fungi and extraordinary prefer to powdery mildew (PM). This study was conducted to investigate the developmental characteristic and the biological control effect on the cucumber PM by the YSL from 2010 to 2012. YSL were detected on the 12 species of host plants infected with PM. and occurrence was observed from the early of July to the early of November in Gyeonggi area. The feeding amount of YSL on the cucumber PM was in order of 4th larva, adult, 3rd larva, 2nd larva and 1st larva. The optimum developmental temperature and photoperiod for YSL was 20∼25℃ and 16L:8D respectively. Three species of fungi were selected as the short term substitution feed for YSL. Control effect on cucumber PM under 2.5% of occurrence rate was linearly increased in proportion to increased numbers of 3rd larva were applied. Combination treatment of the fungal agent with YSL enhanced suppression of cucumber PM more than either agent used alone. The safety agricultural chemicals were selected harmless to the survival of larva and adult of YSL. The survival rate of pupae and adult was over 80% after storage at 10∼12℃ for 30 days. Five species of banker plant were selected for maintenance of YSL during growing season in greenhouse.

Although the greater part of Coccinellidae are all pure entomophagous insects (Weber and Lundgren, 2009), many species of phytophagous, mycophagous and polyphagous ladybirds have been reported in worldwide. This study was conducted to investigate the morphological characteristics of mouthparts of mycophagous ladybird, I. koebelei, comparison with aphidophagous species, Propylea japonica (Coccinellidae: Coccidellini), and developmental charicteristics of I. koebelei at different temperature under incubation conditions. Four species of powdery mildews that I. koebelei fed were observed, and their host plants were pear tree, persimmon tree, red pepper and cucumber. The most conspicuous elements of I. koebelei mouthparts is the mandible. The distal incisor region of the mandible of both species is formed by two teeth, giving them a bifid apex. and the terminal teeth spilt near top and the ventral tooth is smaller than the dorsal one. but the ventral tooth of I. koebelei divided into a row of additional teeth was different with P. japonica. Furthermore, while the inner mandibular cutting edge of P. japonica is smooth, that of I. koebelei is covered in minute teeth, forming a comb. These structures are presumed to help I. koebelei rake fungal spores growing on leaf surface. The developmental period and reproduction ability of were significantly different according to temperature conditions when I. koebelei was fed the powdery mildew from cucumber leaves. The optimum temperature for I. koebelei rearing was from 23 to 25℃ that is the similar condition of cucumber powdery mildew occurrence.