Cross protection is a phenomenon whereby prior infection with one virus (the primary virus) prevents or interferes with subsequent infection by another isolate of the same virus or a closely related virus (the secondary virus), suggesting that cross protection using attenuated viruses appears to offer a promising strategy for biological control of plants viral diseases. A few attenuated viruses have been commercially used as a “vaccine” in Japan. Because cross protection is effective in general, it is necessary to increase good attenuated strains against many severe viruses. To study the underlying molecular mechanism, it is essential to know how the attenuated isolate differs in genome structure from the original virulent isolate.
Seedling damping-off of carrot (Daucus carota L.) was occurred in Ibaraki Prefecture, Japan from August to September, 2008. The causal agent was identified as Rhizoctonia solani anastomosis group (AG) -4 homogeneous group (HG) -I. To the best of our knowledge, this is the first report of this subgroup of R. solani AG-4 as the pathogen of seedling damping-off of carrot in Japan.
Trends in dominant diseases immediately after shifting to lettuce production with or without chemical fertilizers and fungicides, and using conventional or organic cultivation, were investigated in the spring of 2009 to 2011. With organic cultivation, the occurrence of lettuce drop tended to be more severe than with conventional cultivation. Without the application of fungicides, the rates of occurrence of lettuce drop disease in plants cultivated in ultraviolet-absorbing (UVA) film tunnels were lower than in conventional polyolefin film tunnels. UVA film might thus be helpful in controlling this disease in organic cultivation.
Phoma blight and leaf blight of Angelica keiskei occurred in Tokyo. The causal fungi isolated from the diseased plants were identified as Phoma sp. and Rhizoctonia solani AG-2-2 IIIB, respectively. Inoculation tests confirmed that these fungi were the causal agents of the diseases. This is the first report of phoma blight on A. keiskei in Japan and R. solani AG-2-2 IIIB is a new anastomosis group for the pathogen of leaf blight.
Southern blight of winged bean (Psophocarpus tetragonolobus (L.) DC.) occurred on Chichijima in Ogasawara (Bonin) Islands in 2011. A pathogen isolated from the diseased plant was identified as Sclerotium rolfsii Saccardo. An inoculation test confirmed that the fungus was the causal agent of the disease. This is the first report of the disease in Japan.
Cucumber mosaic virus (CMV) was isolated from a tomato plant showing mosaic and systemic necrotic symptoms in Hiratuka, Kanagawa Prefecture, in 2010. In inoculation tests, the isolate (CMV-KT) induced weak mosaic and/or stunt symptoms on tomato, Nicotiana benthamiana, N. tabacum, and Arabidopsis thaliana plants. Sequence analysis of the CP gene suggests that the isolate belongs to CMV subgroup II.
Races of tomato leaf mold fungus were determined which were isolated from tomato leaves in Gunma Prefecture in 2008. Races 4.9 and 4.9.11 isolates were in the eastern region of the prefecture in 2007, and were also from northern and western regions in 2008. Six types of races were isolated at 2008. This result suggests that various races were in the prefecture.
Anthracnose of Kobunagusa, Arthraxon hispidus (Thunb.) Makino. and Lychee, Litchi chinensis Sonn., were found on Hachijo Island of Tokyo Metropolis in 2011. The fungi isolated from the diseased Kobunagusa and Lychee were identified as Colletotrichum destructivum O’Gara and C.gloeosporioides (Penzig) Penzig & Saccardo, respectively. Inoculation tests with the isolates to each host plant showed that the fungi were pathogens of the diseases. These new diseases were named as anthracnose, “tanso-byo” in Japanese.
Verticillium wilt of lettuce (Lactuca sativa L.) occurred in Ibaraki Prefecture in 2009. Isolates from diseased plants were identified as Verticillium dahliae based on their morphological characteristics, mycelial growth response to temperature and sequence analysis of rDNA-ITS region.
Powdery mildew of dandelion (Taraxacum officinale) occurred in Ibaraki Prefecture in June 2010. The powdery mildew already had been known as a disease of the plant. However, this disease had not been reported formally. Hence, we analyzed pathogenicity, morphological characteristics and rDNA-ITS region of the causal agent of the disease, and identified the causal agent as Oidium subgenus Fibroidium. We formally named the disease ‘powdery mildew of dandelion’ as a new disease of the plant in Japan.
Phytophthora blight of southern star (Tweedia caerulea) occurred in Kanagawa Prefecture in September 2008. The causal agent was identified as Phytophthora citrophthora. Phytophthora blight of southern star caused by P. palmivora already had been known. However, symptoms caused by these two pathogens were not distinguishable from each other. Therefore, P. citrophthora should be added as another causal agent of the disease in Japan.
Powdery mildew of Sneezewort (Achillea ptarmica L.) occurred in Tokyo in 2007. The pathogen on was identified as Golovinomyces cichoracearum (de Candolle) Geljuta var. cichoracearum based morphological characteristics. An inoculation test confirmed this fungus as the causal agent of the disease. This is the first report of the disease in Japan.
Bacterial leaf spot by Acidovorax valerianellae is a serious disease for potted hydrangea production in Gunma Prefecture. The effect of temperature and period of high relative humidity on appearance of bacterial leaf spot of hydrangea was investigated. The disease incidence of hydropore at 20℃ and 25℃ were 27.2% and 31.2%, respectively. These incidences were significantly higher than those of 10℃ and 15℃. At 20℃ and 25℃, the disease incidence increased under high relative humidity condition for more than 2 days.
A forecasting method for the emergence of the golden apple snail, Pomacea canaliculata (Lamarck), by using temperature data from the AMeDAS (Automated Meteorological Data Acquisition System), was examined in Chiba Prefecture. The observation of emergence rate of the golden apple snail was carried out at 70 fixed investigation points over the prefecture from 2002 to 2011. The rate of the number of points where more than one individual of the golden apple snail had been observed showed a significant positive correlation (r=0.79, P<0.01)with mean temperature (from December to February). The regression formula, y=2.9557x-10.89 (y: the rate of emergence, x: mean winter temperature), is applicable to forecasting for emergence of the golden apple snail in late May or early June.
Optimum timing of insecticide application for the white peach scale, Pseudaulacaspis pentagona (Targioni), that had infested tea trees was estimated using a simulation method. Fenpyroximate-buprofezin mixture was used as the test insecticide. Mortalities of the larvae (age, 1 to 8 days) of the scale were investigated, after using the insecticide, in a laboratory. In addition, residual activities of the insecticide that lasted up to 4 days after the spraying on the hatched larvae of the scale were investigated in a field and the laboratory. On the basis of these experimental data, and assuming that hatchability is represented as a sigmoid curve, the effects of the timing of the insecticide application on larval mortality in tea fields were simulated. The simulation results showed that larval mortality was the highest at a hatchability of 73.1% and that the optimum application period of the insecticide was 3 days.
Geocoris varius is a native, polyphagous insect predator that attacks many greenhouse pests such as thrips, spider mites and aphids. So far, their pest-control ability was investigated by releasing G. varius nymphs on crops infested with single species of the pests. In this study, we investigated the multiple control efficiency of G. varius on multiple pest species, by releasing their nymphs on watermelon or strawberry plants infested with both thrips and spider mites, or aphids in addition to the two pest groups. In the watermelon fields where thrips, spider mites and aphids occurred simultaneously, G. varius controlled both thrips and spider mites, but not aphids. In the strawberry field where thrips and spider mites occurred simultaneously, G. varius controlled thrips only. Thus, we recommend the use of phytoseiid predatory mites together with G. varius to control spider mites as well as thrips in strawberry fields.
The degree of efficacy and duration period of sterol demethylation inhibiter (DMI) fungicides among many kinds of fungicides against the Japanese pear scab, Venturia nashicola, were investigated through artificial inoculation to Japanese pear (Pyruspyrifolia var. culta) cultivar Kosui grafted seedlings of conidial suspension. Each of the four kinds of DMI fungicides performed with high efficacy, with protective values of 86.7 to 100. A long efficacy duration period was also confirmed, based on the result that there was very little if any occurrence of scab disease as long as 20 days after fungicide application.