Rice false smut caused by Villosiclava virens is a serious rice disease in Japan. To develop new method to control this disease, converter slag was tested to mix into paddy soil and additional application of simeconazole in 2015-2017. Converter slag was apparently suppressed the disease and additional simeconazole applications before heading enhanced the disease suppression. The result indicates that mixing of converter slag in paddy soil has some effects to soil-contained chlamydospores of this pathogen, and is a novel method to control this disease.
We investigated whether tomato plants developing with bacterial wilt causes Ralstonia solanacearum contamination of soil and whether resistant rootstock restrains the transfer of the pathogen to soil in the field. In a susceptible rootstock, migration of the pathogen with a bacterial population close to the detection upper limit was confirmed in all plots in the upper layers of soil, and the migration was detected in 2/3 of plots even in deep soil layers. There was no significant difference in the results of a moderately resistant rootstock from those of a susceptible one. In a resistant rootstock, the migration of the pathogen was detected from only a few plots, and the bacterial population was lower by two orders of magnitude compared with those of a susceptible rootstock. However, it was confirmed that the pathogen transferred to the deep layers of soil even from a resistant rootstock.
For detection of melon necrotic spot virus (MNSV) from infected soils, enzyme-linked immunosorbent assay (DAS-ELISA) has been applied to root samples of melon seedlings, pot-cultivated in the soil for three weeks in a growth chamber at 25°C in 16-h light / 8-h dark conditions. In order to increase the detection accuracy, it was shown that the incubation of sample seedlings should be carried out at 18°C or 20°C. Moreover, MNSV was detected by DAS-ELISA from all samples incubated for two weeks at changing temperature conditions (25°C or 30°C in light and 15°C in dark) showing that the test period was shortened by one week compared to plants incubated at a constant temperature condition (25°C in light and dark).
Fruit reddish tear stain of Citrus flaviculpus ‘Syonan Gold’ has currently become the major disorder in Kanagawa, Japan. From the symptom, a Colletotrichum sp. was constantly isolated. Our pathogenicity test showed that this fungus produced the original symptom, and we thus determined as the causal agent of the disease. On the basis of morphological characteristics and molecular analyses of the actin, calmodulin, chitin synthase, glyceraldehyde-3-phosphate dehydrogenase, rDNA-ITS and β-tubulin regions, the pathogen was identified as Colletotrichum gloeosporioides sensu stricto.
Stem base rot, wilt and blight were found on seedlings or growing plants of Glycyrrhiza uralensis cultivated for experiments in Hokkaido since 2013. Stolon pieces for propagation of the plant rotted from vascular bundles and then bore white molds on both their ends in 2017. Similar fungi were often isolated from the damaged stem base and stolon pieces. The symptoms were reproduced by inoculations with representative isolates from stem and stolon to stem bases of healthy seedlings, and similar fungi were re-isolated from the diseased seedlings. Both isolates formed colonies with white aerial mycelia and yellowish brown to brown reverse side on PDA. Their microconidiophores were straight or slightly curved, smooth, hyaline, septate, sometime blanched, elongated obclubate to cylindrical, with monophialides on the apices, 70.5 - 133.9 (- 160.1) × 2.9 - 5.5 (- 6.9) μm in size. Microconidia were hyaline, 1 or 2-celled, smooth ellipsoid to boat-shaped, 6.0 - 15.9 (- 18.9) × 2.3 - 4.9 (- 5.5) μm in size. Macroconidia were mostly 3-septate, hyaline, smooth, falcate, 25.3 - 40.9 × (3.4 -) 4.2 - 4.9 (- 5.8) μm in size. Chlamydospores were hyaline, thick walled, 1 or 2-celled, sub- spherical to ellipsoid, smooth or verrucose, 7.0 - 11.3 (- 13.3) × 5.8 - 10.4 μm in size. Both isolates were identified as members of the Fusarium solani species complex based on the morphology and rDNA-ITS sequences. We propose the name, Base and stolon rot‘ ( kabugare byo’in Japanese), for this disease new to Japan.
The zoophytophagous insect Nesidiocoris tenuis was released on the garden verbena variant Verbena × hybrida ‘Sunmaref TP-V’ as a banker plant. Verbena plants were planted into the ridges formed by soil-cultured tomato plants in a greenhouse, and the number of N. tenuis present on tomato plants were monitored in 2016 and 2017. Insect numbers were much higher on tomato plants near verbena plants, and also showed an increasing trend over time. These results suggest that verbena plants should be planted densely among tomato plants in order to promote the rapid distribution of N. tenuis throughout the greenhouse.
Conservation biological control (CBC) is the most important strategy for recent integrated pest management systems. For open field cultivations, it is the first step in CBC to clarify the ecological characteristics of native natural enemies by case. In this study, we investigated the occurrence and species compositions of Orius spp. on various types of vegetation from spring to early summer in Hiratsuka City, Kanagawa Prefecture in central Japan for 3 years. Orius spp. occurred firstly on broad-leaved dock and then white clover. The occurrence on eggplant was later than that on zucchini in the same field. Species composition also varied among the types of vegetation. These results suggested the high value of broad-leaved dock and white clover for CBC with native Orius spp. in this area.
Okra Abelmoschus esculentus (L.) Moench is expected to be used as an‘insectary crop’for Orius spp., which are effective natural enemies of thrips in conservation biological control (CBC). In order to obtain basic information, we investigated seasonal occurrences of Orius spp. on some varieties of okra. Orius spp. were observed on every variety of okra. The number of Orius spp. were different among varieties although the effect of their characteristics, such as fruit shape and color, was not clear.