Showing papers on "Leaf spot published in 1976"

Distribution, severity, and relative importance of leaf spot diseases of wheat in western Canada in 1974.

Abstract: The leaf spot diseases spot blotch [Bipolaris sorokiniana], tan spot [Drechslera tritici-repentis], and speckled leaf blotch [Septoria avenae f. sp. triticea] caused insignificant damage to wheat (Triticum aestivum and T. durum) in western Canada in 1974, although infections were widespread. Spot blotch and tan spot occurred commonly in Manitoba and Saskatchewan but were rare in Alberta. Speckled leaf blotch, the least common disease, was found in all three provinces. Artificial inoculations indicated that spot blotch symptoms were distinguishable from those of tan spot and speckled leaf blotch, but that symptoms of the last two diseases were difficult to differentiate. Tan spot and speckled leaf blotch killed infected leaves within 2 1 days. The widespread distribution and potential for foliar damage of D. tritici-repentis indicate that it is the most important leaf spot pathogen of wheat in western Canada.

Mycosphaerella species causing banana leaf spot.

Abstract: A new variety, Mycosphaerella fijiensis Morelet var. difformis is described and its relationship with M. fijiensis and M. musicola is discussed. M. musicola is validated by a Latin diagnosis and the election of a type is made, as no original material exists. The Latin diagnosis of M. fijiensis is also included.

Erwinia mallotivora sp. nov., the Causal Organism of Bacterial Leaf Spot of Mallotus japonicus Muell. Arg.

Abstract: Bacterial leaf spot of Mallotus japonicus, first reported by Takimoto in 1930, was recently found in Japan, and the causal agent was studied taxonomically. The pathogen was assigned to the “Erwinia amylovora group.” The bacterium attacked M. japonicus, producing small, dark-brown spots on leaves as well as shoot blight. Japanese pear, peach, apple, plum, Japanese apricot, and chestnut trees could not be infected. The new isolates differed from E. amylovora in gelatin liquefaction and in ability to produce acid from xylose, mannose, cello-biose, glycerol, mannitol and to utilize formate. The new isolates are regarded as belonging to a new species, for which the name Erwinia mallotivora is proposed. Strain AM1 (= NCPPB 2851) is designated as the type strain. E. mallotivora differs from Aplanobacter mollatii (sic) Takimoto, 1930, the validity of which is considered doubtful.

The effects of Cercospora leaf disease on the growth of groundnuts (Arachis hypogaea) in Nigeria

Abstract: SUMMARY Three experiments with five alternately-branched and one sequentially-branched cultivar of groundnuts are described. Spraying to control Cercospora leaf spot disease doubled the leaf area duration and increased the total weight of a plant by about 65 %. Spraying increased the weight of kernels per plant but in the alternately-branched cultivars also increased the weight of stem and leaves. The proportion of the total dry weight in the kernels in the alternate cultivars was hardly changed by spraying. The sequentially-branched cultivar gave the same increase in total dry weight when sprayed but spraying resulted in a larger increase in the dry weight of kernels. The sequentially-branched cultivar, with few initials for vegetative growth, did not give the same increase in leaf growth.

Zonate leaf spot of jowar caused by Gloeocercospora sorghi and its control through fungitoxicants.

Abstract: G. sorghi produced typical zonate leaf spots on Sorghum vulgare and S. bicolor, damaging up to 85% of the photosynthetic leaf area under humid and cloudy weather conditions. Spores germinated freely in distilled water but required an exogenous nutrient supply for rapid germ tube development. They germinated profusely at 30 deg C and pH 7. Both benomyl and bavistin were highly effective against the fungus in vitro. Under field conditions acidulated benomyl was slightly superior to plain benomyl in reducing disease incidence

Angular leaf spot of strawberry, Xanthomonas Fragariae: First record of its occurrence in Australia, and attempts to eradicate the disease

Abstract: R. N. Pitkethley Animal Industry & Agriculture Branch, Department of the Northern Territory, Darwin, N.T. 5790 A disease of myrtaceous tree seedlings caused by the fungus Cyfindrocladium qulnaueseptetum Boedijn & Reitsma (conidial state of Calonectria autnqueseptete Figue iredo & Namekata) occurred in a forestry nursery at Darwin during the 1975-76 summer wet season. Symptoms of the disease comprise leaf spots (Fig . 1), leaf blight and seedling blight. The leaf spots are irregular to circular, mostly 2-6mm in diameter, with brown centres and red margins. Microscopic examination revealed sporulation of the fungus on leaf lesions and on the stems of blighted seedlings.

Experiments with fungicide sprays to control Ramularia beticola in sugar‐beet seed crops

Abstract: SUMMARY A single fentinhydroxide spray at the end of May controlled Ramularia leaf spot in in-situ sugar-beet seed crops and increased seed yield on average by 4%. Sprays controlled leaf spots most effectively in the Cotswolds, but yield increases were larger in Lincolnshire. Benomyl controlled leaf spot as well as did fentinhydroxide; thiabendazole was less effective, and maneb and cuprous oxide gave poor control.

Fungicidal control of Curvularia leaf spot of maize.

Abstract: Curvularia leaf spot of maize is becoming increasingly important in Nigeria. Six fungicides were tested for their effectiveness in inhibiting the growth of Curvularia pallescens Boed. in culture. The fungicides copper oxychloride, copper oxychloride + zineb and benomyl were more effective than mancozeb, zineb or maneb in inhibiting the growth of C. pallescens in culture; however, only copper oxychloride + zineb and copper oxychloride alone effectively controlled Curvularia leaf spot on maize. Four maize varieties were artificially inoculated in a disease-loss field trial. The yield depressing effect of the disease was found to be significantly dependent on the type of variety infected. Regression coefficients (grain yield versus leaf infection) among the four maize varieties were not statistically homogeneous, percentage grain yield reduction ranged from 3.0 for the variety NCBRbu to 33.3 for the variety Igbira.

Effect of septoria leaf spot in spring wheat

Abstract: A natural infection of Septoria tritici first appeared in an ‘Aotea’ wheat trial at tillering (G.S.3), when the disease occupied 10% of the third-leaf area. Fungicide sprays applied at tillering reduced the severity of the disease for up to 6 weeks. Application of mancozeb or benomyl at ear emergence (G.S.10.1) reduced infection on the flag leaf and leaf 2 by 10-20%, and increased the persistence of green leaf tissue. A yield increase of 14% and 17% over that of the unsprayed plots was achieved, but this increase was not significant under the experimental conditions. The increased yields were due to a significant increase in 1000-grain weight.

Fusarium leaf spot of Celosia argentea L. in Nigeria

Abstract: Fusarium leaf spot is a previously unreported severe disease of Celosia argentea Linn, which is prevalent in South-Western Nigeria, principally in Lagos, Kwara and Western States. The fungus was isolated and identified as Fusarium lateritium Nees. In pathogenicity tests it caused both stem and leaf spots. Two- to 3-week-old seedlings are most susceptible but incidence of the disease in the field is more severe on mature than on younger plants.

Marginal Blight of Cucumber Caused by a Strain of Pseudomonas marginalis (Brown) Stevens

Abstract: A bacterial disease was found on matured lower leaves of cucumber grown under vinyl house conditions in winter of 1974. The disease rarely occurred on inmature leaves soon after unfolding. The disease usually started from leaf edges near hydathodes and quickly enlarged to form V-shaped lesions frequently surrounded by chlorotic areas. These lesions finally coalesced to form the severe blight along the whole margin of the leaf. From these symptoms, “marginal blight of cucumber” was proposed as the disease name. The cultural and biochemical characters of the pathogen were compared with those of Pseudomonas lachrymans, the pathogen of angular leaf spot of cucumber. These two bacteria differed in the important characteristics such as production of fluorecin, degree of gelatin liquefaction, levan formation, margarine hydrolysis, arginine dihydrolase reaction, potato rot, and utilization of sucrose, sorbitol and tartarate. The marginal blight pathogen was rather close to soft-rotting pseudomonads in bacteriological properties. Although the similarity was not complete, therefore, we are inclined to identify the present bacterium as a strain of Pseudomonas marginalis (Brown) Stevens based on the detailed survey of pathological, cultural and physiological characteristics. The isolates of P. lachrymans used in the study showed also some conflicts in physiological properties with the description of the type culture suggesting the presence of strains in this bacterium.

Fungicieds for agriculture and horticulture

Abstract: PURPOSE: To prepare fungicides excellently effective against blast, helminthosporium leaf spot and sheath blight on rice plants, gray mold on vegetables or fruits. COPYRIGHT: (C)1978,JPO&Japio

Selenophoma Leaf Spot, a New Disease of Dendrobium in Japan

Abstract: In 1973, a new disease of Dendrobium was found in Mie Prefecture. In the beginning, small tiny brown spots occurred on either side of the leaves. They shortly developed into round to oval or irregular large spots. The diseased leaves gradually discolored, but spots on them left green borders. Eventually these leaves defoliated. Many pycnidia of a species of the genus Selenophoma were formed on old spots.The result of the artificial inoculation indicated that Dendrobium spp. were susceptible to this fungus, while Cattleya sp., Cymbidium sp., Miltonia sp. and Oncidium sp. did not develop any symptom of the disease. On the basis of differences in morphological characters and host range from the hitherto known species of the genus Selenophoma, the fungus was treated as a new species causing the leaf spot of Dendrobium.Selenophoma dendrobii Abiko, sp. nov.Foliicola; maculis amphigenus, primo brunneis, 0.5-1mm diam., dein griseo-brunneis vel cinereus, 5-10mm diam.; pycnidiis amphigenus immersis dein erumpentibus, brunneis vel atro-brunneis, globosis, 72-120μm diam., ostiolatis; conidiophoris simplicis, hyalinis; conidiis (pycnidiosporidiis) hyalinis, continuis, falcatis, 5-8×1-2μm.Hab. on living leaves of Dendrobium Formidible (S. Takagi) Griggs, Tsu, Mie Pref., Nov. 1. 1973, by K. Abiko (Type). Type: Herb. Vegetable and Ornamental Crops Res. Sta. (=Herb. National Science Museum, F-226369)

Brown Leaf Spot of Physocarpus spp. Caused by Cercospora spiraeicola Muller et Chupp

Abstract: The Cercospora causing brown leaf spot of Physocarpus spp. in Japan was identified as C. spiraeicola Muller et Chupp on the basis of their identical morphological characteristics. Among the inoculated plants belonging to Spiraeaceae, the fungus infected Physocarpus amurensis and P. opulifolius, but not Spiraea spp., Stephanandra spp. and Sorbaria kirilowii, even though, C. spiraeicola had been described on Spiraea prunifolia. Conidia of the fungus overwinter on the fallen diseased leaves. They keep well their germination ability throughout winter and serve as the primary infection source from May to June. Incubation period of the fungus is about two months in spring and one month in summer and early autumn. The fungus may not overwinter within winter bud on the diseased bushes. Conidia germinate and mycelial colonies grow at 10∼35C with optimum temperature of 25∼30C. They germinate well under atmospheric humidity above 98%. H-ion concentration has no influence on not only germination of conidia except pH 3, but also growth of mycelial colonies. Colonies of the fungus grow well on malt extract, potato-sucrose, Saito's soy and Waksman's solution agar.

A new bacterial leaf spot on a Magnolia hybrid

Abstract: During the summer of 1974-75 and the following spring, a leaf spot was observed on a Magnolia campbellii x soulangeana cv. Lennei seedling in a garden at Bilpin, on the Central Tablelands of New South Wales. Investigations have shown that this disease is caused by a bacterium which is possibly an undescribed species. Only two published records of a bacterial leaf spot on Magnolia were found in the literature. Both were recorded on M. soulangeana Soul. and were caused by Pseudomonas syringae van Hall (1, 6).