Showing papers on "Leaf spot published in 1971"

Effect of intensity and quality of light on peroxidase activity associated with Septoria leaf spot of tomato

Abstract: Extracts of tomato (Lyeopersicon esculentum Mill. cultivar Heinz 1350) leaves infected by Septoria lycopersici Speg. were examined for peroxidase activity throughout the period of infection and disease development. These experiments were made to determine whether peroxidase activity was influenced by light, and, if so, the degree of effect of various wavelengths and intensities, other environmental conditions being constant. Consequently, paper electrophoresis scans of peroxidase isozymes showed a bimodal pattern of a conspicuous increase in staining intensity reflecting a high level of enzymatic activity of major components in leaves 4 days after their inoculation with the fungus. At 6 days minimal values were obtained, whereas somewhat enhanced isozyme activity occurred at later stages in the progression of the disease and the maturation of pycnidia and pycnospores. As well, decreased light intensity increased both the severity of the disease and the peroxidase activity in the infected leaf. This effect...

Methods of assessment celery leaf spot (Septoria apiicola) in relation to fungicide evaluation

Abstract: SUMMARY Six criteria for evaluating fungicides for control of celery leaf spot (Septoria apiicola) were compared. Two of these criteria consisted of yield measurements, of which marketable yield gave better statistical separation of the fungicides than gross yield. Of the other four criteria, assessment of leaf spot on a whole-plot basis was the most valuable. Overall disease rating on individual intact plants, rating of each petiole and numbers of diseased petioles per plant were less useful assessment criteria.

Corynespora leaf spot of brinjal

Abstract: Corynespora cassiicola (Berk and Curt) Wei, incitant of leaf spot of brinjal, survives at the room temperatures (28–30° C) for a period of 4 months in infected dry leaves, in infected dead stems for 10 months, and for 11 months in chicken mesh wire house where natural diurnal fluctuating temperatures prevail. Masses of bulbous conidiophore bases appearing like sclerotial bodies, conidiophores and chlamydospores may also help in the survival of the fungus. The weed hostsCroton sparsiflorus Mor.Leucas aspera Spr,Ocimum sanctum L.,Solanum nigrum L., andDigera arvensis Forsk, may act as additional reserviors of inoculum for the disease spread. The fungus survives on chilli crop during summer and this may also serve as primary source of inoculum in July for brinjal crop.

Wheat Leaf Blight and Blotch --- Losses and Control

Abstract: The author discusses two leaf spotting fungi commonly found to cause slight to severe damage to the foliage of spring, winter and durum wheat varieties in North Dakota, Pyrenophora trichostoma, causes a disease called leaf blight, tan spot or yellow leaf blotch, and Lepfosphaeria avenaria f. sp. triticea, which causes a disease called blotch or septoria leaf spot. Both diseases appear as brown spots that spread on susceptible wheat varieties and eventually kill entire leaves. Both the leaf blight and blotch fungus live through the winter in wheat stubble and straw. A study conducted in 1971 to quantitatively chart factors influencing leaf spot severities and wheat loss was conducted at the North Dakota Agricultural Branch Experiment Stations.This is presented. Results indicate that grain farmers can reduce disease severeity and related yield decline by removing infested wheat stubble and growing wheat varieties which are resistant to these diseases. It was concluded that each of these control measures (protective fungicides, removal of stubble and selection of resistant varieties) requires further study.

Perpetuation of Protomycopsis Species Causing Purple Leaf Spot of Legumes in India

Abstract: Protomycopsis patelii Pavgi and Thirumalachar causing angular black spot of Phaseolus mungo L. and P. radiatus L., and Protomycopsis thirumalacharii Pavgi causing purple leaf spot of Sesbania grandiflora Pers. are perpetuated from one season to another through desiccated but viable, heat-resistant chlamydospores in the host residue and those developed in vitro in the soil. The heat-resistant mycelium is later consumed in forming the resting chlamydospores in the soil, thus adding another dimension to the initial soil-borne inoculum potential of the disease.

Banana Leaf Spot caused by Haplobasidion musae

Abstract: (1971). Banana Leaf Spot caused by Haplobasidion musae. PANS Pest Articles & News Summaries: Vol. 17, No. 3, pp. 315-317.

A mycosphaerella leaf spot disease on avocado and its control

Abstract: Summary Avocado trees in Huauchinango, Puebla were affected by an epiphytotic leaf spot disease in the summer of 1968. It caused extensive losses due to a severe defoliation which resulted in the sunburn of the fruit, and undoubtedly in a great reduction of the crop next year. The causal organism was isolated and identified as Mycosphaerella sp. (=Septoria sp.). Field observations of its life cycle revealed that primary infections usually occur in May but the maximum degree of incidence takes place during the rainy season. In order to develop a method of chemical control, two experiments with fungicides were carried out. From the results it can be concluded that with 3 sprays, at monthly intervals, of either Bordeaux Mixture. Captan, Maneb, or Tribasie Copper Sulfate the disease can be satisfactorily controlled.