Rhizoctonia solani Kuhn AG-1 IA causes sheath blight of rice (Oryza sativa) worldwide, seriously lowering yields and quality. Weakly virulent binucleate Rhizocctonia (BNR) isolates sfw-21 from Persicaria longiseta and sfw-26 from Echinochloa crus-galli var. formosensis, collected from nearby paddy fields, were evaluated as biocontrol agents of rice sheath blight. BNR-inoculated rice seeds were tested as a biocontrol treatment after seeds were placed on a 4-day-old culture of BNR for 0 (control: non-inoculated) for, 6, 12, 24, or 48 h before adding to the soil. At the ripening stage, 73–99% of plants had culms with lesions, and lesion height (%) on culms reached 12–23% of the plant height after treatment with 0–12 h-inoculated rice seeds, while culms with lesions (%) was 6–13% and lesion height (%) was 1–2% after treatment with 24–48 h-inoculated seeds, respectively. When plants were treated with BNR at the maximum tillering stage, then inoculated with R. solani AG-1 IA at the heading stage, culms with lesions (%) and lesion height (%) were 5–7% and 1%, compared with 99% and 23%, respectively, for the non-inoculated-BNR treated plants (control). Seedling height (cm) at the initial growth stage, the number of panicles per hill, number of grains per panicles, 1000-kernel weight (g), ripened grain (%) and plant height (cm) at the ripening stage were almost the same regardless of the seed incubation duration with BNR, with a few exceptions. These results indicate that the two BNR isolates have less effect on initial rice growth and yield, and are highly effective in lessening the severity of sheath blight.

To establish a direct PCR method to diagnose Pseudomonas syringae pv. theae (Pst), Acidovorax valerianellae (Av) and A. avenae subsp. avenae (Aaa), that cause browning of tea leaves, we modified previously reported primers specific for Pst and designed primers to specifically amplify sequences from bacterial species that cause bacterial spots and hypersensitivity reactions. The method detected the causative bacteria responsible for browning of tea plant leaves based on the size of the amplified PCR fragment. This technique is convenient for simple diagnosis of bacterial diseases of tea plants.

Cuttings of ‘Reikoudai 1 gou’ line, Ficus erecta, cultivated fig varieties and existing resistant varieties were grown in soil, then a suspension with Ceratocystis ficicola, causative agent of Ceratocystis canker, was poured onto soil, to test whether ‘Reikoudai 1 gou’ was as resistant as F. erecta. After 180 days, 64–100% of cultivated figs and existing resistant varieties were dead; none of ‘Reikoudai 1 gou’ including wound-inoculated, or F. erecta were dead. Thus, resistance to C. ficicola of ‘Reikoudai 1 gou’ is equivalent to that of F. erecta regardless of inoculation method.

In 2019, sweet pepper with wilt and root rot was found in an experimental field of Gifu University. Oospores were observed in the roots, and three rapidly growing isolates with coenocytic hyphae were obtained from the roots and identified as P. aphanidermatum based on morphological features and rDNA-ITS and coxI sequences. This is the first report of this Pythium species as a causal agent of root rot of sweet pepper in Japan.