Showing papers on "Leaf spot published in 1968"

Studies of the rice plant on an “Akiochi” soil in Korea

Abstract: So called “akiochi” soils abound in Korea. Rice plants grown on them are severely infected with Helminthosporium leaf spot, high in iron, and low in potassium, magnesium, manganese, and silica in comparison with those growing on ordinary soils (1). These characteristics closely resemble those of the “akiochi” plants in Japan.

Comparison of some apple latent viruses

Abstract: SUMMARY Apple latent viruses were eliminated from, the tips of apple shoots by exposure to a temperature of 36 °C for various periods. The length of treatment needed to eliminate a particular virus differed from plant to plant, but viruses were always inactivated in the same order: first chlorotic leaf spot, followed by stem pitting and finally Spy decline. Quince plants developed sooty ring-spot and bark necrosis when inoculated with buds from some heat-treated apple clones infected with Spy decline virus. Only chlorotic leaf spot virus was transmitted to herbaceous hosts by sap extracts from apple leaves, petals and fruits, and returned from herbaceous plants to apple. This virus, isolated from either apple or cherry, caused a dark green mottle on peach leaves.

Microorganisms Existing on Leaves of Rice Plants and the Occurrence of Brown Leaf Spot

Abstract: In this paper microflora, especially of fungi, on the surface of apparently healthy leaves of rice plants is discussed. The second leaf from the top of variety Nakate Shin-Senbon was used for isolation, and many fungi, such as Candida, Rhodotorula, Penicillium, Alternaria, Aspergillus, and bacteria were isolated. Among them Candida sp. was most frequently isolated. The presence of Candida or other fungi in the conidia suspension of Cochliobolus miyabeanus did not disturb the conidia germination of the latter. However, if the mixed inoculation of Cochliobolus with Candida was performed to rice plants, number of the brown leaf spots decreased, representing about 50 per cent of the control. No microorganism, isolated from leaves of rice plants, inhibited the mycelial growth of C. miyabeanus on agar media.

Leaf spot of bananas caused by Mycosphaerella musicola: action of oil on the life cycle of the pathogen

Abstract: Oil spray reduced germination, germ tube growth, and appressoria formation by spores of Mycosphaerella musicola under field conditions for periods varying from 2 days to 2 weeks. Inhibition occurred only when spores were on the same leaf surface to which oil was applied. Appressoria formation and germ tube growth were reduced up to 33% and 25%, respectively. Conidia and ascospore production and dissemination were not adversely affected by oil spray. However, there were fewer sporodochia and perithecia in spots that were slow to develop as a result of oil spray. Oil application up to 2 weeks before or after infection increased the incubation period and the generation time, and reduced the number of spots. Oil is effective in retarding spot development when applied either before streaks appear or at the yellow streak stage of disease development. Oil, when applied during the incubation period or to yellow streaks, causes a variable amount of reduction in spotting and in only a minority of cases is disease d...

Studies on taphrina maculans butler, inciting leaf spot of turmeric (curcuma longa L.). I. Isolation of the pathogen

Abstract: T. maculans inciting leaf spot of turmeric is difficult to be isolated into a pure culture. The best stage of the spot development on turmeric which yielded successful isolations was either the initial or the middle stage expressing yellowish necrotic areas. The successful course of development of asci, ascospore and conidia has been worked out. By streaking ascospore and conidial suspensions, the spot bearing portions of leaves on the inner side of the lid thus placing them in hanging position above the plates poured with cleared and acidified potato dextrose agar or turmeric leaf decoction agar or by streaking sterile water washings from the chocolate brown spots on these media, it was possible to isolate successfully the pathogenic culture ofT. maculans at 20° C.

Relative Damage of Cercospora Leaf Spot In Sugarbeet Varieties

Abstract: In 1948, Stewart (2)2 reported the results of a spraying ex­ periment to co ntrol leaf spot caused by CeTcospora beticola SacCo Cnder severe and prolonged exposure, the productivity of sprayed populations of the most resistant sugarbeet ,ariety, US 216, was over twice that of the unsprayed diseased population. In 1965, an ("xperiment was undertaken at the Plant Industry Station, Beltsville, Maryland, to reappraise losses caused by leaf spot, particularly the production loss, in the current resistant variety. Summer temperature and humidit) at this station are favorable for the disease. A sprinkler system was used to promote infection during periods of drought.

The causal organism of celery leaf spot, Septoria apiicola

Abstract: Examination of Septoria collections on Apium spp. from world herbaria and fresh collections confirm the findings of Gabrielson & Grogan (1964) , that only one species, S. apiicola Spegazzini, is involved. This conclusion is substantiated by cross-inoculation.

Studies on Taphrina maculans Butler, inciting leaf spot of turmeric (Curcuma Longa L.). II. The disease development and life cycle of the pathogen

Abstract: The course of development ofT. maculans since its entry into the host till the full development of spots together with its morphological characters have been investigated and discussed.

Studies on taphrina maculans butler inciting leaf spot of Turmeric (Curcuma Longa L.). III. Perpetuation and transmission of the disease

Abstract: The pathogenT. maculans inciting leaf spot of turmeric perpetuates in the form of ascospores and conidia and incites first infection on the lowermost leaves, in October and November when the atmospheric humidity prevails about 80 % with 21°–23° C temperatures. The secondary infection is due to availability of large potential of inoculum of ascospores and conidia frequently and periodically produced by the pathogen under cool temperature conditions (20°–24° C) with about 80 % atmospheric humidity. Plant debris, rhizomes etc. of the previously affected crop or soil from the fields where turmeric crop was taken in the previous season do not serve the primary source of infection.