To evaluate the effect of a reflective net (Slimwhite®45) and timing of insecticide application on suppressing lisianthus (Eustoma grandiflorum ) necrotic ringspot disease caused by Iris yellow spot virus (IYSV), the incidences of vector thrips (Thrips tabaci ) and necrotic ringspot disease were examined in Karatsu City, Saga Prefecture, Japan in 2007. In a survey plot with reflective net, the total number of captured T. tabaci on a sticky trap outside and inside the greenhouse were lower than those without reflective net. The incidence of necrotic ringspot disease was lower when insecticide (acephate) treatments were timed with the emergence of viruliferous T. tabaci. The disease incidence was drastically reduced when the adjusted insecticide treatments and reflective net were used together.
Gentian tumorous symptoms have been known in Nagano, Iwate and other prefectures since 1985. Previously undescribed virus-like particles were found in gentian (Gentiana spp.) plants collected in Iwate Prefecture that had galls or tumors on stems and roots. In transmission electron micrographs of ultrathin sections of tissue from symptomatic plants, virus-like isometric particles about 60 nm in diameter, which had dense cores about 40 nm in diameter with less dense outer shells, were scattered or aggregated in small masses in the cytoplasm of phloem parenchyma cells and in the sieve tubes of galls or tumors. Virus-like particles were observed in stems, crowns and roots but not in leaves and petals. Similar particles were detected by negative staining using uranyl acetate or phosphotungstic acid (pH 7.0) in homogenates of roots fixed with glutaraldehyde.