As. J. Food Ag-Ind. 2009, Special Issue, S145-S154 Asian Journal of Food and Agro-Industry ISSN 1906-3040 Available online at www.ajofai.info Research Article Efficacy of Xenorhabdus sp. (X1) as biocontrol against for controlling mushroom mites (Luciaphorus sp.) Siriphan Sobanboa 1 , Prapassorn Bussaman 1* and Angsumarn Chandrapatya 2 1 Department of Biotechnology, Faculty of Technology, Mahasarakham University, Mueang District, Maha Sarakham 44000, Thailand. 2 Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkaen, Bangkok 10900, Thailand. *Author to whom correspondence should be addressed, email: prapassorn.c@msu.ac.th Abstract We investigated the efficacy of symbiotic bacteria to control the mite (Luciaphorus sp.) which is a pest of several mushroom species. Six species of symbiotic bacteria, Xenorhabdus sp. (X1), X. nematophila (X2), X. poinarii (X3), Xenorhabdus sp. (X4), Photorhabdus luminescens (P1) and P. luminescens akhurstii (P2), were evaluated. A cell suspensions (1x10 8 cells/ml) of Xenorhabdus sp. (X1) caused 82.5% mite mortality. Mortality varied with bacterial culture age, 2-day old culture had 82.5% mortality and 3- day old X1 bacterial cultures had 74.17%. In addition, the bacterial culture when grown at an optimal temperature (30 ๐ C) killed mites at a mortality rate of 83.33%. The cell-free supernatant of X1 was also found to effectively kill the mushroom mites at a rate as high as 90.83%. Furthermore, the cell-free supernatant of 2- and 3- day old X1 culture resulted in mites mortality of 87.5 and 78.33%, respectively. In conclusion, this study has shown that all symbiotic bacteria tested appeared to have miticidal activity. Both the cell suspensions and the cell-free supernatant of Xenorhabdus sp. (X1) bacteria has miticidal properties and has the potential as a biocontrol agent for controlling mites infesting the cultivated mushrooms. Keywords : Xenorhabdus sp., Luciaphorus sp. and biological control Introduction Luciaphorus sp.(Acari: Pygmephoridae) is considered to be one of the most destructive pests of several commercial mushrooms species, including Lentinus squarrosulus, L. polychrous, Auricularia auricula and Felmularia velutipes, These mushrooms are widely cultivated in the North and the Northeast of Thailand (Bussaman et al., 2004). This mushroom mite can be