The bulb mite (BM), Rhizoglyphus echinopus, is hard to control in the harvested onion and garlic. Methyl bromide (MeBr) fumigation is the only option to eradicate BM at present. However, MeBr causes phytotoxic damage (index 3) to onion and garlic and highly toxic to fumigators. To replace MeBr, we evaluated ethyl formate (EF) and phosphine gas (PH3) to BM at 5℃ which is current practical fumigation temperature. The >140 g·h m-3 of EF for 24 h could completely control BM and this CT (concentration × time) product was slightly (index 1) phytotoxic to onion and garlic. Fumigation of 2 g PH3 required >120 h exposure to kill 100% of BM without any pyhtotoxic damage. Further researches are being planned to shorten the exposure time with synergistic effect between EF and PH3.

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 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.