Biological control has emerged due to the side effects of chemical control such as residual and toxicity. One of the biological controls is entomopathogenic fungi. The entomopathogenic fungus used in this study was first detected in the insectary. The fungus was identified as Lecanicillium sp. based on the sequences of the ITS1 and 2 regions. Lecanicillium sp. infects aphids, scale insects and whiteflies, especially Myzus persicae and Aphis gossypii. In this study, we characterized the fungal phenotype, growth condition, and pathogenicity against green peach aphid. Mycelial growth of Lecanicillium sp. was 12.79±0.46 mm diameter during 7days on potato dextrose agar at 25℃. In addition, the fungus was able to annihilate 100% green peach aphids, after 8days of inoculation. Ultimately, this study would be provide new information on Lecanicillium sp. and suggest the potential utilization of this fungus as a biological control agent.

The development of entomopathogenic fungi has received increasing interest as part of integrated pest management strategies as biocontrol agents. It is reasonable to assume that entomopathogenic fungi might produce secondary metabolites modulating juvenile hormone for their survival against defense mechanisms of host insects. In this study, acetone extracts of 189 entomopathogenic fungi cultured on unpolished rice medium were screened for their juvenile hormone antagonist (JHAN) activities using the yeast-two hybrid system. Among 14 extracts showing JHAN activities, extract of the F-145 showed high level of insecticidal activities against both Plutella xylostella and Aedes albopictus. This isolate was identified as Lecanicillium attenuatum. These results suggested that the Lecanicillium attenuatum could be useful for development of eco-friendly insecticides.

Entomopathogenic fungi have been widely studied for their potential as the effective biological control agents. They produce variety of secondary metabolites with insecticidal activities, and it is reasonable to assume that entomopathogenic fungi might produce secondary metabolites modulating juvenile hormone for their survival against defense mechanisms of host insect. In this study, acetone extract of the Lecanicillium spp. cultured on unpolished rice medium showed juvenile hormone antagonist (JHAN) activity in the yeast-two hybrid β-galactosidase assay and high insecticidal activity against Aedes albopictus and Plutella xylostella. In addition, to compare bioactivities of secondary metabolites from solid and liquid culture, the Lecaniciilium spp. strain cultured on unpolished rice medium or PDB medium were serially extracted with acetone and ethyl acetate respectively. Both extracts showed JHAN activity and high insecticidal activity against A.albopictus. Theses results suggested that secondary metabolites of entomopathogenic fungi could be useful for development of novel IGR insecticides.

Cultural characteristics Lecanicillium lecani Btab01 and its insecticidal activity against tobacco whitefly (Bemisia tabaci) were investigated. On potato dextrose agar, tryptic soy agar and SDA+Y media, mycelial growth of L. lecani Btab01 was best at 20~25℃ and suppressed above 28℃. Both solid culture and liquid culture of L. lecani Btab01 showed high insecticidal activity, 93.9 and 98.3% respectively, against nymph of tobacco whitefly, but there is no significant difference. When culture of L. lecani Btab01 was treated at the concentration of 10⁵, 10⁶, 10⁷ and 10⁸ cfu/ml, their insecticidal activity were 5.8%, 33.8%, 77.3% and 98.5% respectively, and LT<SUB>50</SUB> values were 16.1 days, 7.3 days, 5.1 days and 3.5 days respectively. When nymphs were treated by the cultures of L. lecani Btab01 and maintained under saturated condition for zero hour, 24 hours and 168 hours, their control activities were 0%, 20.3% and 100% respectively. Spore germination of L. lecani Btab01 was increased about two times by adding edible oil. When L. lecani Btab01 was treated to control nymph with 0.1% edible oil, it showed high control activity (98.6%) compared to single treatment of L. lecani Btab01 (79.9%).

Sweet potato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is a serious pest of many economically important crops. The insect has developed resistance to chemical insecticides. Therefore, the development of microbial agent such as entomopathogenic fungi, Lecanicillium lecanii is necessary. Spores of L. lecanii Btab01 was collected after cultivation on solid PDA and liquid RB (rice bran amended with 2% molasses) media. The bioassay was carried out with B. taabci nymphs for 7 days at 25℃ and 60% relative humidity. Further, mortality was corrected with appropriate controls. The results revealed that spores obtained from RB medium caused high mortality (98.31%) compared to PDA medium (93.94%). Spore concentrations 105, 106, 107, and 108 colony forming units (c. f. u) ml-1 caused 5.81, 33.80, 77.27, and 98.54% mortality, respectively. The mortality (100%) was observed for 4 days when L. lecanii spores was mixed with 0.1 - 0.3% soybean oil. Hence, it is concluded from this study, L. lecanii Btab01 cultivated on RB medium can be recommended to control the nymphs of B. tabaci. Spore suspension can be expected to high efficacy when soybean oil was blended.

Sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), is a serious pest of many economically important crops. The insect has developed resistance to chemical insecticides. Therefore, the development of microbial agent is necessary. Among the several entomopathogenic fungi, Lecanicillium lecanii Btab01 which has high insecticidal activity was carried out this experiments. To develop mass culture, we subcultured L. lecanii Btab01 on PDA, TSA, SDA+Y, RA and GSA media at 25℃ incubator to select the optimal solid culture medium. Hyphal growth was measured every 3 or 4 days. L. lecanii Btab01 grew fastest in RA, followed GSA, SDA+Y, PDA and TSA. L. lecanii Btab01 was cultured on PDB, TSB, SDB+Y, RB, GSB media at 25℃, 180rpm shaking incubator to select the optimal liquid medium. Spore germination was measured by spread plate method every 12 or 24 hours. Spore germination appeared 7.8×108 CFU/ml after 4 days in RB, followed GSB (5.5×108 CFU/ml), SDB+Y (2.7×108 CFU/ml), TSB (1.7×108 CFU/ml) and PDB (0.6×108 CFU/ml).