The bulb mite (Rhizoglyphus echinopus) damages garlic, shallot and onion in the bulbs, corms and tubers. It has recently become a serious problem because of the continuous use of acaricides resulting in resistance among bulb mite population. Thus, there is need to find alternative control measures to suppress bulb mite population. Here, we report the screening result of pathogenic fungi for the control of R. echinopus. Initial screenings were performed using 352 isolates of entomopathogenic fungi from Korea soils. As results, 15 isolates of acaropathogenic fungi showed the pathogenicity to bulb mite supporting fungal conidiation. These isolates were identified as 3 isolates of Metarhizium flavoviride var. pemphigi and 12 isolates of Metarhizium pingshaense by microscopic examination and genetic sequencing of the ITS region and elongation factor-1 alpha. Selected 15 isolates were tested for their virulence against adult R. echinopus and the thermotolerance and the activity to UV-B irradiation of conidia. Additionally, the activities of chitinases and proteases produced by M. pingshaense were compared according to the medium. These acaropathogenic fungi would be considered promising for biological control of bulb mite.

The two-spotted spider mite, Tetranychus urticae Koch, is an economically important pest of crops of plant grown in the field or greenhouse worldwide. It has recently become a serious problem because of the continuous use of acaricides resulting in resistance among spider mite population. Thus, there is a need to find alternative control measures to suppress spider mite populations. In this study, we report the screening result of pathogenic fungi for the control of spider mite. Initial screenings were performed using 352 isolates of putative pathogenic fungi from Korea soils. As results, 11 strains of acaropathogenic fungi were isolated from 8 cadavers of spider mite supporting fungal conidiation. These isolated were identified as four isolates of Beauveria bassiana (6, 2R-3-3-1, 2R-4-5, 2R-4-7), two isolates of Metarhizium anisopliae (4-2, 2-2), one isolate of Clonostachys rosea 5-2, one isolate of Lecanicillium attenuatum 4-1, one isolate of Pochonia suchlasporia 2R-3-1, one isolate of Aspergillus flavus 7 and one isolate of Isaria lilacinus 2R-4-6 by microscopic examination and genetic sequencing of the ITS region. Based on the screening results, eleven isolates were tested for their virulence against adult spider mites. All fungal isolates were pathogenic to spider mite but mortality varied with isolates. These acaropathogenic fungi may be useful to develop eco-friendly acaricide to control two-spotted spider mite.

The bulb mite (Rhizoglyphus echinopus) is damage garlic, shallot, onion in the bulbs, corms, tubers. It has recently become a serious problem because of the continuous use of acaricides resulting in resistance among bulb mite population. Thus, there is need to find alternative control measures to suppress bulb mite population. Initial screenings were performed using 352 isolates of pathogenic fungi from Korea soils. As results, 9 strains of acaropathogenic fungi were cadavers of bulb mite supporting fungal conidiation. These isolated were identified as 8 strains of Metarhizium anisopliae (4-1, 4-3-1, 4-3-2, 4-8-1, 4-4-1, 4-14-2, 4-16-1,and 4-31-2), 2 strains of Beauveria bassiana (4-4-2) by microscopic examination and genetic sequencing of the ITS region. However, ITS sequence analysis was consistent with the Metarhizium anisopliae (4-1, 4-3-1, 4-4-1, 4-31-2; a, 4-8-1, 4-14-2, 4-16-1; b, 4-3-2; c). Therefore, genetic diversity of selected in vitro isolates was characterized by Universally Primed (UP) PCR. The divided with Metarhizium anisopliae 4strain by UP-PCR. Of the 5stain isolation tested, 5stain resulted in mortality rates ≥20% within 6 days and all fungal treatment was detected mycosis. Thus these species of acaropathogenic fungi can be considered promising for biological control of bulb mite.