This study was conducted to develop economic injury level (EIL) and economic threshold (ET) of onion thrips, Thrips tabaci on welsh onion (Allium fistulosum L. var). The changes of welsh onion biomass and T. tabacci density were investigated after introductions of T. tabacci at different densities and days: By the results of the experiment in the early welsh onion cultivation periods (30d after transplanting), the biomass of welsh onion significantly decreased with increasing the initial inoculated density of T. tabacci. The relationship between cumulative insect days (CID) and yield loss (%) of welsh onion was well described by a nonlinear logistic equation. Using the estimated equation, EIL and ET of T. tabacci on welsh onion were estimated at 24 and 20 CID per plant, respectively. By the results of the experiment in the late cultivation periods of welsh onion (about 120d after transplanting), the welsh onion biomass was also significantly different inoculation thrips densities to welsh onion. The EIL and ET were calculated as 35 and 28 thrips per welsh onion plant. Until a more elaborate EIL-model is developed, the present result may be useful for T. tabacci management during the cultivations of welsh onion.

This study was conducted to evaluate the effects of temperature and nematicides on endospore attachment characteristics of 2 Korean isolates of nematodeparasitic bacteria, Pasteuria penetrans. P. penetrans CJ-1 and 98-35 isolates and 3 species of root-knot nematodes in U. of Florida were used ; Meloidogyne incognita (MI), M. arenaria (MA), and M. javanica (MJ). Three nematicide levels of 2, 4, and 6 ppm were compared by treating Vydate and Nemacur in the endospore containing soils. The endospores were attached to the root-knot nematode juveniles by centrifugal method. Reproduction of the isolates was checked by observing root-knot nematode females harvested from inoculated tomato roots. 1. Among the two Korean isolates, 98-35 showed attachments to MI, MA, and MJ juveniles, but it could not reproduce in any species. CJ-1 reproduced on all the 3 tested root-knot nematode species. 2. Endospores pretreated in -14°C showed higher attachment rate than those pretreated in 4, 24, and 40℃. 3. Nemacur treatments significantly suppressed the attachment of the endospores to the juveniles, while Vydate treatment effects were negligible.

A storage mite (cheese mite), Tyrophagus putrescentiae, is known as the pest in storing grains and common health pest species in the dust around home. The mite directly affect our well-being as parasites, vectors of disease, and producers of allergens. But recently we found damages in horticultural crops especially in greenhouses. It is very difficult to diagnose the damage by the mite because of the tiny size of the mite. And the symptom is not clear at the beginning stage. In this study, observations were done on the mite and the crop damage symptoms in several horticultural crops under dissecting microscope and scanning electron microscope (SEM). The mite body size was 0.3~0.5㎜ and they had long hairs all around their body when observed under SEM. The characteristic damage symptoms in some horticultural crops are as follows. In phalaenopsis, the flower buds became yellow and the lower side of the leaves had white spots. The surface of young cucumber fruits became shiny and soft at the early damage stage. In the crops, the damaged surfaces became corky as the plants grew up. In peach tree, whole the trees lost vigor and flower drops were observed when the mite density was very high in greenhouse cultivation.