Bacterial rot of soffron is a typical disease of the tubers, roots, sheaths, foliages and flower stalks. The worst damage is due to the tuber lesions. The primary detection of the disease in Japan is at 1909 and the disease has recently become most serious and widespread, The lesion is destructive when successive cultivation is kept on and also when the diseased tubers are transplanted. The causal organism is a peritrichiate bacterium which is described herein as Bacillus croci, n. sp. It grows readily on various culture media, producing white, round colonies. It produces acid but no gas with carbohydrates and is very resistant to high temperatures and tolerable to a high acidity. Isolution of the organism has been accomplished repeatedly from rot-tuber or decayed sheath. Inoculations of healthy tubers or sheaths with pure cultures produce a rapid, soft decay of sheaths and a tuber-rot. The organism remains on the rot part of saffron plant and in the infected soil. The disease is mainly disseminated by transplanting the disease tubers. Although no means of control has been yet worked out, selection of healthy tubers and disinfection of the seed tubers in saturated lime water for half an hour seem to be advisable.
Since 1913, an undescribed bacterial leaf spots of Hibiscus has been under observation in Korea. The most noticeable lesions in leaves are found as irregular black spots which cause the distortion of the leaves. The causal bacteria have been isolated repeatedly and its pathogenicity proved by inoculation with pure culture. The disease is briefly described as follows: Symptoms: The disease affects the cotyledons, especially young leaves when 2-3 leaves are expanded, but reduced when the plants matured. The first signs of the disease are minute circular black spots which enlarge in size gradually and take circular or irregular outlines, then finally the margins become angular limited by the veins. The outer parts of the spots take on obscure whitish yellow colour or water soaked appearance, and when the leaves are severely attacked the whole plants become blackend and dry out. Description of causal organism: Bacterium Hibisci, n. sp. A cylindrical rod with rounded ends, single or pairs usually and chains frequently, 1.2-2. O X 0.6-0.7 μ. in size, motile by means of 1-2 polar flagella, no spore or capsule formed, Grams-negative, and stains well in carbol fuchsin, anilin water gentianviolet, and aqueous methylenblue; in agar plate, the surface colonies are smooth and circular with entire margin, slightly elevated in center, wet shiny and cement-like coloured by reflected light, fine granular in center under magnification; bouillon culture clouded after 20 hours at 25-27°C, and rim produced with heavey precipitate; gelatin slightly lignified, milk slowly peptonized, no gas produced, nitrate slightly reduced, no reaction of indol, thermal death point at 49°C, aerobic. Infection experiments Inoculation by needl puncture with water suspension of 24 hours agar culture resulted characteristic leaf spots but inoculation by spraying failed to give infections. When the seeds soaked with water suspension of agar pure culture are sowed, the germinated young plants showed lesions of bacterial blight on the cotyledons. Our experiment shows that this organism overwinters on seed. In April 1921, the seeds were disinfected for 10 minutes with mercuric chloride (One to 1000 part of water) or hot water treatment (55°C) and then sowed in large tube with sterilized sand. The plants germinated, grew soundly and no disease was observed, but the plants from untreated seeds showed 50 per cent diseased leaves. Control: Our experiments for control during the season of 1919 and 1920 show that the seed disinfection is very effective, application of 5-5-50 bordeaux mixture spray greatly reducing the disease.
1) The present paper deals with the thermal effect on the germination of the conidia, the growth of the mycelium and the formation of the conidia of Helminthosporium Oryzae, and also the thermal death point. 2) The optimum temperature for the germination of the conidia lies between 20° and 30°C., at which temperature the greatest germination percentage (70 percent or more) of conidia is secured. 3) The minimum temperature for conidia germination is 2°C. The germ tubes produced at this temperature, are spherical or elliptical and pronouncedly swell up, and never linear, as those of normal shape are. 4) The maximum temperature for conidia germination is 41°C., at which the germ tubes are also spherical or elliptical, but smaller than those formed at 2°C. 5) The best growth of the mycelium was secured at a temperature between, 27° and 30°C. 6) The maximum temperature for the formation of the conidia is between 35° and 38°C., and the minimum temperature 5°C. 7) Conidia formed at the optimum temperature, are obclavate and curve to one side; those formed at 5°C. are cylindrical and straight and have a smaller number of the septa; and those at 30°C. are shorter and wider than those formed at 20°C. 8) Conidia formed at lower temperature are dark in color, and become lighter with the rise of temperature. 9) The thermal death point (in 10 minutes exposures) for the conidia is 50-51°C.; and for the germinated conidia on hyphae 48-50°C.
1) The present paper deals with the brown shot hole disease of cherry leaves caused by Mycosphaerella cerasella Aderh., which is known as the ascigeuous stage of Cercospora cerasella Sacc. 2) Investigations on the causal organism were carried out chiefly on the morphological characters of its conidiophore, conidium, perithecium, ascus and ascospore by the writer under the directions of Mr. Y. Nisikado, Plant Pathologist of the Ohara Institute. 3) This disease is not only common in Prunus cerasus, but also in Prunus Yamasakura var. typica, Prunus. Yamasakura var. spontanea subvar. hortensisP. Itosakura and P. Itosakura var. subhirtella in the western parts of Japan.' 4) The genetic relation of Cercospora cerasolla Sacc. and Mycosphaerella ferasella Aderh. has been demonstrated by comparative cultural studies of the isolations secured from both ascigenous and conidial stages. 5) The parasitic nature of the present fungus has been ascertaind by successful inoculations carried out on above described five varieties of the cherry (Prunus spp.)
1. The spores of Cercospora beticola kept in dry condition at the laboratory were active for 16 months. 2. The spores infected in the seeds were able to germinate until the end of April (sowing season) of the next year. 3. The spores of diseased leaves kept under caves were not able to germinate in the beginning of May, but sclerotial bodies or mycelia in tissue were alive through the winter. 4. The spores of diseased leaves placed on the soil in the field of Suwon, lose thier vitality in the beginning of May but the sclerotial bodies or mycelia in tissue were very often able to germinate. The same result was obtained in Heijo, but a few spores on the under parts of the pile were able to germinate in the case where beet root were covered with thin layer of soil. 5. The spores of diseased leaves mixed with the wet soil died after 3 to 4 weeks, in the laboratory.