Abstract
Differences in population growth of the Robine bulb mite (Rhizoglyphus robini CLAPAREDE) were observed using three types of rakkyo (Allium chinense G. DON) bulbs; healthy, injured (by mechanical cutting), and Fusarium-infected bulbs. Within the short period of 14 days, bulb mites penetrated the infected bulbs and showed and exponential population growth. On the other hand, few mites could penetrate healthy bulbs and population increase was low even at 35 days after release. It required 60 to 90 days for the mites to finally penetrate the healthy bulbs and show an exponential population growth. On the injured bulbs, the population increase of mites was higher than on the healthy ones, but much lower than that on the fungi-infected bulbs. These results suggest that earlier penetrations of mites result in a faster population growth of subsequent infestations.
