Tal Hanuny and Moshe Inbar - Department of Evolutionary and Environmental Biology, University of Haifa, Mount Carmel, Haifa 31905, Israel

We determined the pest status of the bulb mite, Rhizoglyphus robini, on young onion plants with and without the presence of different fungal species. First, we analyzed the degree of attraction of the mite to various fungi found on onion. We then assessed the effects of selected fungi and the mite on the germination and subsequent survival of young onion seedlings. Finally, we examined how the interactions between a weakly pathogenic fungus and the mite would affect the onion seedlings. The mites were always more attracted to colonized PDA plugs versus non-colonized PDA (except in the case of binucleate Rhizoctonia AG-A). Onion seedling survival was significantly reduced by the fungi; the most pathogenic being the Fusarium moniliformae white strain and the least being F. moniliformae purple strain. Onion sprouts colonized by this fungus were significantly more attractive to the mites than healthy sprouts. At two days post-mite infestation, the effects on onion sprout length of the mites and the F. moniliformae purple strain and their interaction were significant. Mites had no effect on sprout length in the absence of this fungus, in contrast, in its presence, mites significantly reduced sprout length, more than the fungus alone. The importance of host-plant, fungi and mite interactions are discussed.