Red-necked longhorn beetle, Aromia bungii (Faldermann) (Coleoptera: Cerambycidae) is a serious pest of peach and plum tree in China. It has recently invaded into Japan and attacking Prunus trees, such as cherries Prunus × yedoensis 'Somei-yoshino', peaches Prunus persica and ume Prunus mume. The invasion of the beetle was firstly confirmed in 2011 and now it distributes through seven prefectures in Honshu and Shikoku islands. Nine years have passed after its invasion and we have developed some protection methods. Biology and controlling methods of A. bungii are demonstrated in this article.
The symptoms of alternaria leaf spot and leaf blight diseases on welsh onion are similar and cannot be distinguished visually. To research the occurrence of these diseases, brown leaf spots appearing on welsh onions were collected from lower leaves in western areas of Shizuoka Prefecture every month from August to December in 2013, 2014 and 2015. Conidia on the spots were removed with cellophane tape and then observed for disease diagnosis under microscopic observation. The occurrence of alternaria leaf spot was lower than that of leaf blight at rates from 36.4% to 2.6%, except for 60.0% on September 2013. It was proved that the main pathogen of brown leaf spots was leaf blight in the western area of Shizuoka Prefecture.
Sclerotinia rot of Dianella ensifolia Sims and Tetragonia tetragonioides (Pall.) O.Kuntze occurred in Tokyo. Our inoculation test showed that isolates obtained from diseased plants were the causal agent of these diseases. Both isolates were identified as Sclerotinia sclerotiorum. This is the first report of Sclerotinia rot of D. ensifolia and T. tetragonioides, caused by S. sclerotiorum in Japan.
Rice stripe virus (RSV), which causes chlorotic stripes, mottling, and necrotic streaks on rice (Oryza sativa L.), is one of the major causes for yield losses at some places in Kanto area, Japan. Controlling small brown plant hopper (SBPH, Laodelphax striatellus), a vector of RSV, using chemical insecticides is crucial to decrease RSV infection in such regions. To optimize the timing of spraying the insecticides in paddy fields for distinct regions, the emergence date was predicted by the effective cumulative temperature method using temperature data obtained from the Agro-meteorological Grid Square Data System. The predicted dates of the second instar nymph of SBPH in five distinct locations (one each in Mito and Tsukuba, and three in Chikusei) in Ibaraki Prefecture were June 8, May 31, June 5, June 10 and June 1, which were less than 2 days apart from the emergence date determined by surveys in the actual fields. Therefore, this prediction would be effective to reduce the damage caused by RSV.
We investigated the seasonal prevalence of Orius spp., which are widely known as important natural enemies of thrips, in a research field of ‘edamame’ (immature green soybean) in Kawasaki City. The populations of Orius spp. were observed on ‘edamame’ but there was no clear correlation to flowering term as reported previously. The occurrence of Orius spp. followed thrips, and then suppressed their populations. These results are important basic information for conservation biological control (CBC) in the area.
The zoophytophagous bug Nesidiocoris tenuis (Reuter), a promising natural enemy of small insect pests, is known to injure tomato plants under certain conditions by its phytophagy. However, there is little information on damage by this mirid bug to tomato varieties cultivated in Japan. In this study, we evaluated the potential for injury by N. tenuis to Japanese tomato variety ‘Momotaro York’. We exposed one N. tenuis adult for 14–15 days to each part of tomato plants, namely, the seedlings, the growing points, and the trusses with flower buds, flowers, and immature fruits. In the seedlings, wounds and necrotic rings appeared on the leaves and stems, but no damage was observed on the fruits harvested after transplanting. The bugs did not affect the growing points and the trusses of tomato plants. These results suggested the low possibilities for damage by N. tenuis to this tomato variety
We found an infection of Pratylenchus coffeae RFLP phenotype-A nematodes on Chinese yam, Dioscorea polystachya, in 2018 in Chiba Prefecture, Japan. Tubers harvested in a farmer’s field and tubers grown in nematode-inoculated pots both showed the same symptoms of dry rot. The fresh weight (mean±SD) of the tubers of inoculated plants was significantly smaller (13.9±6.3 g) than that of the control (27.7±9.4 g; p<0.05). These results indicate that P. coffeae RFLP phenotype-A can cause surface damage and yield loss in Chinese yam.
The population of the tobacco cyst nematode Globodera tabacum was examined for the ability to reproduce on several rootstocks for eggplant. Although G. tabacum produced many cysts on Solanum integrifolium rootstock cultivar Akanasu, no cysts were produced on S. torvum rootstock cultivars Tonashimu and Torero. We then examined the suppressive effect of S. torvum cultivar Torvum vigor and tomato rootstock cultivar Doctor-K on the population density of the nematode in soil. Torvum vigor and Doctor-K were resistant to G. tabacum. Nematode egg and second-stage juvenile densities in soil were reduced after cultivation with those rootstocks.
The sugar beet cyst nematode, Heterodera schachtii Schmidt, is an economically important pest of sugar beet (Beta vulgaris L.), and the nematodes occurrence had not been confirmed in Japan. However, in September 2017, H. schachtii was detected on roots of Brassica sp. cultivated in a field in Hara Village, Nagano Prefecture, Central Japan. The host plant range of H. schachtii is broad including crops of Brassica, Beta, Rheum and Spinacia spp. The impact of H. schachtii spread is of immeasurable importance in Nagano Prefecture because it is a production area specialized in Brassica crops. Since April 2018, emergency measures to eradicate H. schachtii and to prevent its spread have been implemented with application of lime nitrogen and multiple treatments of fumigants. As one of the measures to prevent recurrence of H. schachtii, the difference in control effects among various nematicides should be examined. In this paper, we report the control effects of nematicides registered on crops mainly produced in the H. schachtii outbreak area. We found that soil fumigants were generally effective. Non-fumigants, which were easy to handle and applied just before planting or seeding also had some control effects although not as highly effective as the fumigants.
From March 2016 to March 2017, we investigated seasonal population dynamics of the exotic predatory mite, Phytoseiulus persimilis estimated to have colonized tea fields in Shizuoka Prefecture, Japan. Species of phytoseiid mites in the tea field investigated were P. persimilis, and native species: Amblyseius eharai, A. obtuserellus, Neoseiulus womersleyi, and Euseius sojaensis. The percentage of P. persimilis in the species composition were 5.6% (2 Jul.) and 26.0% (6 Sept.). P. persimilis adults with eggs were found on 23 Mar for the first time. The two peaks of occurrences were observed on 25 Apr. three weeks after the peak of Tetranychus kanzawai, and on 23 Aug. two weeks after the peak of T. kanzawai. P. persimilis was not observed after the middle of Sept.. Primary dominant species of native phytoseiid mites was A. eharai, they occurred during most of the seasons. The peaks of native phytoseiid mites were observed on 24 May and 9 Sept., after the peaks of P. persimilis. Indices of ω proposed by Iwao (1977) which indicates a special association between two species were calculated among T. kanzawai, P. persimilis and Amblyseius spp. The indices between T. kanzawai and P. persimilis changed plus (coexistence distribution) to minus (exclusion distribution) around Apr. - May. These results suggest that P. persimilis strongly depends on T. kanzawai, while P. persimils does not significantly affect the populations of native phytoseiid mites in tea fields.
Emergence of Eriophyes chibaensis Kadono and the leaf mosaic symptoms caused by the species on Japanese pear, which can be suppressed well by spraying machine oil in early-March, tolfenpyrad in early-May and chlorfenapyr in mid-May, were shown to be suppressed by spraying spirotetramat in late-April even better and for a longer period of time. Sulfoxaflor, which has been reported effective for the rust symptom by the species, was not effective for the leaf mosaic symptoms.
In order to establish a method for testing spider mite susceptibility to acaricides that can be performed easily in agricultural extension centers or field conditions, we devised a method and determined its usability by utilizing body fluid stains of spider mites crushed in an envelope, hence the “Envelope Method”. We examined the relationship between the mortality in the envelope method, which was tested by counting stains of living spider mites and mortality in the conventional spray method. There was a trend for mortality in the envelope method to be lower compared to the conventional method. However both methods were positively correlated. Furthermore, since traces of body fluids of adult female spider mites are easily confirmed by unaided eyes, use of equipment such as a loupe is not necessary in most cases. From these observations, the envelope method was suggested as a simple and efficient method in testing the susceptibility of spider mites to acaricides at agricultural extension centers or field conditions.