Annual Report of The Kansai Plant Protection Society

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In one of our fields, almost all tomato plants were wilted by a bacterial pathogen, Ralstonia solanacearum, if no plant protection treatments were applied. On the field, grafting a cultivar for harvest onto a cultivar tolerant to the pathogen delayed occurrence of wilt. In another hand, we enhanced the water permeability of the soil by mixing with rice chaff and plowing to a depth of 70 cm before sterilizing the soil with hot water (95°C, 250 L/m²). Thus, the percentage of wilted tomato plants decreased to less than 40%. A biocontrol agent, Pseudomonas fluorescens FPT-9601 and FPH-9601, which were mixed in soil for early seedlings, did not suppress the occurrence of wilt. Hot water treatment without enhancing the water permeability of the soil was not effective for plant protection. The temperature of soil at 50 cm depth reached to 60°C when hot water was poured in the soil after enhancing the water permeability; this temperature was sufficient to kill the pathogen. However the temperature at this depth was 35°C when hot water was poured in untreated soil. The density of the pathogen was maintained around or below 10² colony forming units (cfu)/g of dried soil, which is the limit of detection for the pathogen, in the field after enhancing the water permeability of the soil and pouring hot water, but the density was more than 10³ cfu/g in the field without any treatment or with hot water only, before wilt occurrence in each year.

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In 2007, I determined the densities of phytoseiid mites and yellow tea thrips Scirtothrips dorsalis Hood on the windbreaks of bigleaf podocarp trees Podocarpus macrophyllus that surround citrus orchards in Nishiura and Mikkabi region in Shizuoka prefecture. In the Nishiura region, phytoseiid mites such as Amblyseius eharai, Euseius sojaensis, and Neoseiulus californicus were observed on the windbreaks throughout early May to late July. In the Mikkabi region, phytoseiid mites were not detected on the windbreaks in May, but the density of phytoseiid mites increased slowly on the windbreaks from early June to early July. The total number of phytoseiid mites observed between early May and late July on the windbreaks in the Nishiura region was greater than that in the Mikkabi region. And consequently, the number of S. dorsalis larvae and adults observed on the windbreaks between early June and late July in the Nishiura region was smaller than that in the Mikkabi region. These results suggest that phytoseiid mites can lower the density of S. dorsalis on windbreaks of bigleaf podocarp trees.

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The wheat variety "Nishinokaori" showed the highest susceptibility for foot-rot disease caused by Ceratobasidium gramineum among the four wheat varieties cultivated in Mie Prefecture. Increasing of acreage of "Nishinokaori" in Mie Prefecture may be an reason of recent occurrence of foot-rot disease in wheat. The lesion of foot-rot appears in around April. In Mie Prefecture, occurrence of foot-rot was most severe, when "Nishinokaori" was seeded in the early November. The disease was decreased when seeded in the middle November. The disease was hardly shown when seeded in the late November. Seeding later than the middle November was effective in order to control foot-rot disease. Seed treatment of the azoxystorbin was highly effective and practical to control the disease.

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Effect of the predatory mite, Amblyseius swirskii Athias-Henriot on the population of melon thrips, Thrips palmi Karny was investigated on eggplant in greenhouses without a heater in 2009 in Osaka Prefecture. In the released plots in five places, 25-50 A. swirskii per square meter were released for control of the thrips once or twice from March to May, respectively. A. swirskii colonized on leaves and flowers, the population densities of the thrips became lower in the released plots than in the control plots after the releasing. The injury to eggplant fruits by the thrips became lower in the released plots than in the control plots. The results suggest A. swirskii is effective as an agent for controlling the thrips on greenhouse eggplant.

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