Insect-proof nets are one of the best safeguards to inhibit Tomato yellow leaf curl virus (TYLCV) infection by Bemisia tabaci (Gennadius). Nets with more cross meshes prevent B. tabaci invasion but growth of tomato seedlings can be affected. Insect-proof nets with 3 mesh sizes were compared and nets with a 0.4×0.4mm mesh did not affect seedling growth. On the other hand, a net with 0.4×0.4 mm mesh size was less effective than neonicotinoid granules in preventing infection of TYLCV and invasion of B. tabaci Q biotype but a combination of the two methods significantly inhibited TYLCV infection. This combination was the most effective for inhibiting infection during tomato seedling growth.
群馬県内のオクラ苗立枯れ症状発生圃場の菌種を調査したところ，17圃場中13圃場でPythium ultimum var. ultimum が分離され，本菌がオクラ苗立枯病の主要な病原菌であることが判明した。本菌汚染圃場において，5月播種の平坦部露地栽培条件下で，2週間おきに播種期を違えてオクラを播種したところ，地温が低い上旬に播種すると発病が多く，健全株が少なくなることが確認された。さらに，オクラ播種後に長繊維不織布（商品名：パオパオ90）を2週間程度べたがけ被覆した結果，無被覆に比べ地温が高くなり，発病が抑制され，健全株が多くなった。
Downy mildew of sweet scabious (Scabiosa atropurpurea) occurred in Chiba Prefecture in November 2004. The causal agent was identified as Peronospora knautiae. This is the first report on sweet scabious in Japan.
Rhizoctonia rot of sultan snapweed (Impatiens sultanii ) occurred in Kanagawa Prefecture on September 2008. The causal agent was identified as Rhizoctonia solani AG-2-2 IIIB. This anastomosis group is added to the pathogens of Rhizoctonia rot of sultan snapweed in Japan.
Myrothecium leaf spot of hybrid bouvardia Bouvardia × hybrida occurred on Oshima Island of Tokyo Metropolis in 2008. The causal fungus isolated from the diseased hybrid bouvardia was identified as Myrothecium roridum Tode:Fries. Inoculation tests showed that this fungus was the causal agent of the disease. This is the first report on the disease in Japan.
A bacterial disease on leaves of potted hydrangea (Hydrangea macrophylla (Thunb.) Ser.) has occurred in Gunma Prefecture. Twenty bacterial isolates from the affected hydrangea were identified as Acidovorax valerianellae by investigating bacteriological properties and by analyzing the sequence of 16S rRNA. The isolates associated with the bacterial leaf spot of hydrangea were pathogenic to H. scandens ssp. chinensis, H. paniculata f. grandiflora (Sieb.) Ohwi and melon in addition to H. macrophylla as the original host.
Imidacloprid and related neonicotinoid insecticides have been used since 1995 in tea fields in Shizuoka Prefecture against tea green leafhopper, Empoasca onukii Matsuda. Field control tests on E. onukii using imidacloprid or related neonicotinoids have been conducted in our research center every year. These results showed injury prevention rate on new shoots were over 97% until 2002, although the results showed rates less than 50% since 2004. The explanation for this is that the pesticide resistance to neonicotinoids of E. onukii populations in tea fields increased since around 2003.
On August, 2006, at a tea field in Saitama Prefecture, some larvae of ground beetle were observed in the colonies of tea tussock moth Euproctis pseudoconspersa caterpillars. The beetle larvae were collected and reared on the caterpillars in the laboratory. After the adults emerged, they were identified as Parena cavipennis. In the field, a significant positive correlation was observed between the density of caterpillar colonies of tea tussock moth and that of P. cavipennis (r=0.7171, p<0.01). In the area of 100m2, 20 caterpillar colonies occurred on average, and about 3 individuals of the ground beetle were observed. The coloration of the beetle larvae is yellow and white with black spots on the dorsal abdomen, which resembles the tea tussock moth caterpillar. In addition, it was observed in a tea field that the caterpillars did not flee from the beetle larvae, even if the beetle larvae existed in the caterpillar colonies. Thus, I speculate that the coloration of the beetle larvae is a mimic coloring and camouflage to avoid the escape of the moth larvae.
It is necessary to control Bemisia tabaci (Gennadius) Q biotype for inhibition of Tomato yellow leaf curl virus (TYLCV) infection. In a test with insecticide applied to growing tomato seedlings, nitenpyram and dinotefuran soluble powders were useful for control of B. tabaci Q biotype but were not able to prevent TYLCV infection. On the other hand, granular formulations prevented TYLCV infection far more than soluble powders even if the same chemical agent was applied. However, the granulars did not provide acceptable inhibition of TYLCV with B. tabaci Q biotype, so it is necessary to consider other methods to prevent TYLCV infection.