In the long-mat type hydroponic rice seedling method, rice seeds were soaked into hot water at 60°C or 62°C for 15 minutes to control the bakanae disease instead of using seed disinfectants. Germination rate of the hot-water soaked seeds was 6%-12% lower than the non soaked seeds, but the seedlings grew normally on the seedling beds and field. Using infected seeds, the number of bakanae plants on the seedling beds and field was reduced by the hot water treatment and did not differ significantly from a seed disinfectant treatment. These results suggest that soaking the seeds into hot water before sowing is effective against bakanae disease and could be used in the hydroponically raised seedling method.
Damping-off of celery (Apium graveolens L.) occurred in Hachijo Island of Tokyo Metropolis in 1999. A Rhizoctonia species isolated from the diseased plants was identified as Rhizoctonia solani Kühn. Inoculation tests showed that the fungus was the causal agent of the disease. This is the first report of the disease in Japan.
Phytophthora rot of garden pea (Pisum sativum L.) and Albuca nelsonii N. E. Br. occurred in Hachijo-Island of Tokyo Metropolis in 1999. A Phytophthora species isolated from diseased plants was identified as Phytophthora nicotianae van Breda de Haan. Inoculation tests showed that this fungus was the causal agent of these diseases. This is the first report of these diseases in Japan.
Monoconidial isolates of Venturia nashicola were collected in 1999 from ten pear orchards in Tochigi Prefecture and their susceptibility to the DMI fungicide fenarimol was determined by mycelial growth tests. Results on PDA plates showed that DMI-resistant isolates occured at 5.9% on average and suggested that field performance of this fungicide is still maintained in Tochigi Prefecture.
The occurrence of the black bean aphid, Aphis fabae Scopoli (subsp. fabae) was observed on broad beans in Osaka Prefecture. Since the first record of A. f. fabae in Japan (Hokkaido Prefecture) in 1994, its distribution has not been reported in the western part of Japan. The offspring of parthenogenetic females collected in Osaka Prefecture did not produce any sexual forms under the short day-length (8L16D, 12L12D) and low temperature (10°C, 15°C) conditions which induce sexual generation of this species with holocyclic life cycle. So it was supposed that the aphids of Osaka Prefecture belong to the anholocyclic population. This aphid could be reared on Visia faba, Phaseolus vulgaris, P. angularis, Pisum sativum, Beta vulgaris, Rumex obtusifolius but not on Trifolium repens.