Pythium root-rot of Sandersonia aurantiaca Hook. occurred on the island of Hachijo, Tokyo, between 2000 and 2001. Two species of Pythium isolated from the diseased plants were identified as Pythium irregurale Buisman and P. splendens Braun. Inoculation tests showed that these fungi were the causal agents of the disease. This is the first report of the disease in Japan.
Gray mold and leaf tip blight of Ruscus hypoglossum L. occurred on the island of Hachijo, Tokyo, in 2000. A Botrytis species isolated from the infected plants with gray mold was identified as Botrytis cinerea Persoon: Fries, while a Cladosporium species isolated from the infected plants with leaf tip blight was identified as Cladosporium cladosporioides (Fries) de Vries. Inoculation tests showed that these fungi were the causal agents of the associated diseases. This is the first report on these diseases in Japan.
Leaf spot symptoms occurring on the plants Calathea louise Gagnep., C. zebrina (Sims) Lindl., Ctenanthe oppenheimiana (E. Morr.) K. Schum., Maranta leuconeura var. erythroneura Bunt., M. leuconeura var. kerchoviana E. Morr., and M. leuconeura var. leuconeura E. Morr. were detected on the island of Hachijo, an administrative area of the Tokyo metropolitan government. The pathogen isolated from leaf spots present on the above plants was a fungal species in the genus Bipolaris. Calathea, Ctenanthe and Maranta plants inoculated with the Bipolaris sp. produced the same disease symptoms. The inoculation test demonstrated that this fungus was the causal agent of the leaf spot of these plants. This is the first report of this disease in Japan.
Root rot of Eustoma grandiflorum was reported on the Island of Izu-Oshima, Tokyo in 1998-1999. A Pythium species isolated from diseased plants was identified as Pythium irregulare. Inoculation experiments showed that the fungus was the causal agent of this disease for Eustoma grandiflorum.
Viral symptoms with necrotic spots and necrotic ring spots were found in cyclamen (Cyclamen persicum) and exacum (Exacum affne) plants in Tochigi prefecture. The double-antibody sandwich enzyme-linked immuno-absorbent assay with antiserum to Tomato spotted wilt virus (TSWV) gave a negative reaction. Spherical enveloped particles were observed with electron microscopy in infected cyclamen leaves. Degenerate primers specific to the nucleocapsid genes of Impatiens necrotic spot virus (INSV) and TSWV were designed for reverse transcription-polymerase chain reaction (RT-PCR). RT-PCR gave the expected PCR products of approximately 540bp and 440bp. Sequence comparison of the PCR products showed 99.1% and 98.8% homology with INSV (NL-07) in nucleotide and amino acid, respectively, indicating that the causal agent of necrotic spot diseases of cyclamen and exacum was INSV.
Detailed observation of ovipositional lesions made on leaf sheaths of rice plants by rice planthoppers revealed that the mean lesion length on the epidermis was significantly longer and the mean number of injured parenchymal tissue walls was significantly larger in Sogatella furcifella than in Nilaparvata lugens. Formation of watery lesions that have a close bearing on the ovicidal response of rice plants was induced by Sogatella-type and Nilaparvata-type artificial injury made on leaf sheaths at the rate of 55.2 and 65.5%, respectively. This result gives the first evidence for the induction of an ovicidal response in the absence of chemical substances derived from planthoppers.
Thrips palmi Karny is the most serious pest of greenhouse melon in Japan. The predatory mite, Amblyseius cucumeris Oudeman, was released in melon greenhouses during the summer growing season to control T. palmi. In trial 1, approximately 100 A. cucumeris per plant were released on melon leaves 3 times; 3, 4 and 5 weeks after planting. The density of T. palmi in released greenhouses were 25% of that in the unreleased control greenhouses, and the injury index of leaves was 40% of that in the control 4 weeks after the first release. In trial 2, A. cucumeris was released on soil at the base of each plant. The predatory mites were released 2, 7 and 14 days after planting at a density of 100 mites per plant. The density of T. palmi in released greenhouses was 6% of that in unreleased greenhouses 5 weeks after the first release, and the injury index of leaves was 33% of that in the control 7 weeks after the first release. These results suggest that A. cucumeris was effective in reducing the numbers of T. palmi on greenhouse melon, and that the most effective timing of first release was just after planting.
Adult females of Thrips palmi Karny given 6 powdered sugars as a nutrient source and distilled water were able to survive for longer periods of time in the presence of each of the sugars than in the presence of distilled water alone. The results suggest that T. palmi is able to consume powdered sugars. The percentage of T. palmi surviving after 15 days was greatest with glucose at 56% followed by fructose at 40%, maltose, sucrose, and trehalose in decreasing order of survival. Raffinose had the lowest survival of thrips at 12%.
Thysanopteran species collected on the islands of Ogasawara from 1983 to 1992 were identified to 8 species of Thripidae that belong to Elixothrips, Selenothrips, Heliothrips, Hercinothrips, Thrips and Scirtothrips, and to 3 species of Phlaeothripidae belonging to Haplothrips. For some of these species, new locality records were given.
White blemishes occurred on the rind of Satsuma mandarin fruits cultivated in greenhouses of Numazu City, Shizuoka Prefecture in 2000. Blemished fruits were present in 21 greenhouses (70% of all greenhouses within the city) with an area of 134 a (81.2% of total greenhouse area). All insects collected from 7 damaged Satsuma mandarin fruits were identified as Thrips tabaci. This species accounted for 95.2% of all insects, 720 individuals, collected on yellow sticky-traps from 25 May to 7 June in a greenhouse. Experimental infestation of T. tabaci adults collected from leek caused the same kind of damage on ripe Satsuma mandarin fruits. T. tabaci made minute vacant spaces in the rind by piercing and sucking the surface tissues and the blemished part became whitish.
Adult western flower thrips, Frankliniella occidentalis Pergande, were given 6 sugar solutions of various concentrations as the sole nutrient-source to investigate the sugars that are metabolized. Fifty-percent or more of the adult thrips given the majority of the sucrose solutions of 1-45% (w/v%), glucose solutions of 5-30%, fructose solutions of 5-30%, maltose solutions of 10-25%, and trehalose solutions of 15-25% survived for 15 days on each of the respective sugar-solution concentrations. Adult thrips given only distilled water were all dead within 6 days. These results are evidence that western flower thrips utilize the 6 sugars.
Pot studies on the effects of methionine (Met) and fungivorous nematode, Aphelenchus avenge (Aa) on plant growth and pathogens' propagation in tomato-Meloidogyne incognita (Mi)-Fusarium oxysporum f. sp. lycopersici (Fo) pathosystem were carried out using a multi-factor factorial experiment design of 24. Regarding interactions between Met and Aa on pathogens' propagation and their damage to tomato plant, a synergistic effect was detected for final populations of Mi juvenile and an interference effect for Fo densities 49 days after planting, but there were no evident interactions for root-knot index or number of fallen leaves that were affected most by Fo treatments. Interactions between Met and Aa on tomato-growth-characters were evident for the dry root weight only but not for the shoot length, shoot weight, number of flowers or total fruit weight. Met as such significantly (p≥0.05) contributed to reduce the Mi juvenile population and root-knot index 70 days after planting and Fo densities for both 21 days and 49 days after planting. Fruit weight was significantly improved (p<0.05) by Met treatment when the soils were inoculated with Mi. Aa alone did not contribute significantly to the improvement of tomato growth, Fo and Mi control or root-knot index. Results led to the conclusion that the combined application of Met and Aa may be impractical for the simultaneous control of Mi and Fo on tomato.