Showing papers on "Leaf spot published in 1980"
TL;DR: The incidence of leaf spot infection was greater in the spring than in the autumn, particularly during the period of extension growth and early flowering, whereas the incidence of stem canker infections was greater at the end of flowering.
Abstract: SUMMARY
The main source of Leptosphaeria maculans (Desm.) Ces. & de Not. infection on winter oilseed rape in Cambridgeshire was stubble debris from the previous season. Heavy leaf spot infection of seedlings near unploughed oilseed rape stubble resulted in complete crop loss. The fungus actively colonised stubble debris after harvest and perithecia were formed predominantly on tissues colonised during this period. Ascospores were detected throughout the year, mainly from October to April. The degree of leaf spot infection in the autumn was correlated with stem canker infection at the end of flowering and with severe stem lesions at harvest. The incidence of leaf spot infection was greater in the spring than in the autumn, particularly during the period of extension growth and early flowering. Stem canker infections were first seen in March and continued to develop up to and after harvest.
98 citations
TL;DR: Tests in Britain on samples of basic and commercial Brassica oleracea seed between 1976 and 1978 showed that many lots were infected with Alternaria brassicicola, which transmitted the disease but seedling infection was more closely correlated with the latter.
Abstract: SUMMARY
Tests in Britain on samples of basic and commercial Brassica oleracea seed between 1976 and 1978 showed that many lots were infected with Alternaria brassicicola. A. brassicae was uncommon in basic seed in these years and in commercial seed harvested in 1976 and 1977 but was frequent in seed harvested in 1978. Most affected seeds were contaminated by surface-borne spores and mycelium of A. brassicicola but many were internally infected by the fungus situated within the seed-coat and in some seeds in the embryo tissues. Superficial contamination by the fungus declined rapidly after 2 yr in cabbage seeds stored at 10 °C, 50% r.h. but internal infection persisted for up to 12 yr. In some samples, internal infection was commonly associated with small shrivelled seeds. Surface contaminated and internally infected seeds transmitted the disease but seedling infection was more closely correlated with the latter.
74 citations
TL;DR: The hypothesis that cytokinins have a role in suppressing necrosis is supported by the fact that exogenously applied cytokinin also inhibits the necrosis caused by HgCl2.
Abstract: The application of leaf spot inducing bacteria or HgCl2 to lower leaves of Xanthi-nc tobacco, or systemic virus infection by cucumber mosaic virus increased the cytokinin level and induced resistance to tobacco mosaic virus (TMV), the development of local lesions, in the upper leaves. Acquired resistance (protection) induced by different agents was manifested by suppression of the necrotic reaction in the upper leaves after inoculation by TMV, rather than by inhibition of multiplication of the virus. The hypothesis that cytokinins have a role in suppressing necrosis is supported by the fact that exogenously applied cytokinin also inhibits the necrosis caused by HgCl2. Root formation by derooted Xanthi-nc tobacco plants (which had previously been inoculated by bacteria or virus or treated by HgCl2) was strongly inhibited, which also suggests an increase in cytokinin levels in inoculated plants. Stresses caused by treatment of the lower leaves of tobacco plants with viral, bacterial, or with mercuric chloride increase cytokinin levels in the untreated leaves. At the same time, to the necrosis usually caused by TMV is controlled in these leaves.
48 citations
TL;DR: This is the first record of the natural occurrence of the teleomorph (perfect state) of the species in New Zealand.
Abstract: In May 1978 a severe epidemic oflight leaf spot occurred in crops of cauliflowers (Brassica oleracea L. var. botrytis L.), cabbages (B. oleracea L. var. capitata L.), and sprouting broccoli (B. oleracea L. var. italica Plenck) in parts of the Pukekohe district. Conidia produced on lesions associated with the disease were typical of those of Cylindrosporium concentricum Greville, previously reported to be the causal pathogen. Three months later numerous small black apothecia were found on decaying petioles, veins, and occasionally lamina tissue of fallen leaves from these crops. When vegetable brassica seedlings were inoculated with ascospore suspensions obtained from these apothecia typical symptoms oflight leaf spot developed 11-14 days later. The apothecia were identified as those of Pyrenopeziza brassicae Sutton et Rawlinson. This is the first record of the natural occurrence of the teleomorph (perfect state) of the species in New Zealand.
24 citations
TL;DR: Study of the F1, F2, and F3 progenies indicated that PLB 257, carries a recessive gene imparting resistance to angular leaf spot, which is a serious disease of French bean in the hills of India.
Abstract: Angular leaf spot (Isariopsis griseolaSacc.) is a serious disease of French bean in the hills of India and 40 to 70 per cent of the green pods are damaged and rendered unmarketable. Crosses were made between PLB 257, (Phaseolus coccineus L.), a red flowering pole tope, resistant to angular leaf spot, and Contender (Phaseolus vulgaris L.), a highly susceptible commercial cultivar. Studies of the F1, F2, and F3 progenies indicated that PLB 257, carries a recessive gene imparting resistance to angular leaf spot.
22 citations
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TL;DR: Among 49 strawberry varieties tested, Morioca 16 and Robinson were highly susceptible to the disease by artificial inoculation and Catskill, Cyclone, Northwest, Merton princess, Juspa and Daehak I were moderately susceptible whereas 31 varieties were resistant.
Abstract: A new disease of strawberry caused by Alternaria was found in Gim Hae, Gyougnam province, in July 1979. The symptoms of the disease occurred mainly on leaves as showing dark brown spots with circular to irregular, in diameter. The pathogen was identified as Alternaria alternate (Fr.) Keissler which has not been described in Korea as a pathogen of strawberry disease. The common name of the disease was given as Gum un mum byung of strawberry. The conidia shape and size of this fungus varied considerably with culture media. The measurements of conidia and beak on corn meal agar were , respectively, which were shorter than those on strawberry leaf lesions in the field. Among 49 strawberry varieties tested, Morioca 16 and Robinson were highly susceptible to the disease by artificial inoculation and Catskill, Cyclone, Northwest, Merton princess, Juspa and Daehak I were moderately susceptible whereas 31 varieties were resistant. This fungus could also infect the leaf of Common garden sunflower, Double sunflower and Mexican sunflower among the 14 plants species tested.
11 citations
TL;DR: Symptoms and signs on the evergreen and deciduous host species are described in detail and Morphologically, 25 Japanese collections occurring on 9 host species could not be divided into clearly separated groups.
Abstract: Severe leaf spot disease of Pomoideae, Rosaceae caused by a species of Entomosporium has recently been observed in Kyushu and the central to western parts of Honshu, Japan. Symptoms and signs on the evergreen and deciduous host species are described in detail. Morphologically, 25 Japanese collections occurring on 9 host species could not be divided into clearly separated groups. Germination of conidia and growth of mycelial colonies were studied under various conditions.
10 citations
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10 citations
Journal Article•
TL;DR: Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content.
Abstract: (1980). Leaf spot of cherry laurel caused by Pseudomonas syringae. Canadian Journal of Plant Pathology: Vol. 2, No. 4, pp. 235-238.
TL;DR: Responses indicate that inherent resistance or susceptibility expressed by P. pratensis to pathogenesis by D. sorokiniana is regulated in part by leaf age (developmental senescent stage) and by photomorphogenically defined light quality.
Abstract: Photomorphogenic light definitions were derived by mathematical determination of the estimated phytochrome photoequilibrium for each light treatment spectrum. A wide range of photomorphogenic light treatments represented by spectra with estimated phytochrome photoequilibria of 0.45, 0.54, 0.60, 0.67, and 0.71 was utilized to determine the influence of photomorphogenically defined light on resistance of Poa pratensis L. to pathogenesis by Drechslera sorokiniana. Accurate resolution of D. sorokiniana leaf spot development required evaluation of separate leaf ages due to the sequential appearance, development, and senescence of P. pratensis leaves. Disease development (all light treatments) was greatest on leaf 4 (oldest, postmature) followed by leaf 1 (youngest, premature). Low levels of disease occurred on leaves 2 and 3 (mature). Photomorphogenic light defined by estimated phytochrome photoequilibria greater than 0.60 (natural light ≃ 0.60) was most disease promotive on leaf 1. Conversely, photomorphogenic light defined by estimated phytochrome photoequilibria of less than 0.60 was most disease promotive on leaf 4. These responses indicate that inherent resistance or susceptibility expressed by P. pratensis to pathogenesis by D. sorokiniana is regulated in part by leaf age (developmental senescent stage) and by photomorphogenically defined light quality. A hypothesis is presented and discussed which integrates and speculates on these observations with respect to the literature.
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TL;DR: The increase and distribution of resistant strains of the cherry leaf spot fungus in Michigan is reported, including benomylresistant C. hiemalis, which is particularly important economically considering the 4,553 ha of sweet cherries and 16,616 ha of sour cherries grown in the state.
Abstract: JONES, A. L., and G. R. EHRET. 1980. Resistance of Coccomyces hiemalis to benzimidazole fungicides. Plant Disease 64:767-769. Benomyl-resistant strains of the cherry leaf spot fungus (Coccomyces hiemalis) were detected in a sour cherry orchard in 1975, in another in 1976, and in three sweet and four sour cherry orchards and a fruit tree nursery in 1979. Sensitive isolates were strongly inhibited in a disk assay at 1.0 pg/ ml benomyl; resistant strains were weakly inhibited at 800-1,000 /g/ ml. Resistant strains developed in orchards where benomyl had been used exclusively for 3-5 yr and where mixtures of benomyl and nonsystemic fungicides had been applied after 1975, the year a resistant strain was first detected. The isolates were also resistant to carbendazim and thiophanate-methyl. Additional key words: Prunus avium, P. cerasus Cherry leaf spot, incited by the fungus Coccomyces hiemalis Higgins, commonly occurs on sour and sweet cherries in Michigan. The disease is particularly important economically considering the 4,553 ha (11,244 acres) of sweet cherries and 16,616 ha (41,028 acres) of sour cherries grown in the state (1). An annual program of four to six fungicide applications is used to prevent early defoliation of cherry trees from the disease. In 1975, we detected benomyl-resistant Monilinia fructicola (Wint.) Honey on cherries in Michigan and stated, without presenting supporting data, that benomylresistant C. hiemalis was also identified (5). In 1979, leaf spot was a problem in some cherry orchards where benomyl was mixed or alternated with nonsystemic fungicides. Therefore, we sought to determine if benomyl-resistant strains of leaf spot were present in these orchards. In this paper we report the increase and distribution of resistant strains in the state. To our knowledge, benomylresistant C. hiemalis has not been detected in other cherry-growing areas. MATERIALS AND METHODS The techniques used to detect resistant strains were similar to those used for Venturia inaequalis (Cke.) Wint. (6,8). Leaf disks containing single lesions were cut with a number 3 cork borer from This research was supported in part in 1979 by the North Central Regional Pesticide Impact Assessment Program and in 1975 and 1976 by the Michigan Association of Cherry Producers. Journal Series Article 9354 of the Michigan Agricultural Experiment Station. 0191-2917/80/08076703/$03.00/0 @1980 American Phytopathological Society infected cherry leaves and streaked sequentially across divided petri dishes containing potato-dextrose agar (PDA; GIBCO Diagnostics, Madison, WI 53711) in one half and PDA supplemented with 25 pg/ ml benomyl in the other. Fresh stock solutions of benomyl50% a.i. WP were added to the media after autoclaving and cooling to about 60 C. About 30 disks, with no more than two disks per leaf, were cut from leaves taken from a composite sample of leaves collected in each orchard. Conidia that germinated and produced normal germ tube elongation on the benomylamended medium in about 24 hr were considered resistant. Isolates for further study were obtained by transferring single spores from the PDA plates to 60-mm-diameter petri dishes containing PDA or lima bean agar (Difco Laboratories, Detroit, MI 48201). Conidia of each isolate were produced on lima bean agar slants as described by Magie (7). Resistance to other fungicides was determined by dipping sterilized 12.7-mm-diameter assay disks into solutions containing 0, 1, 10, 100, 500, and 1,000 /g/ml fungicide and by placing a saturated disk in the center of each petri dish seeded 5 hr earlier with 0.5 ml of conidial suspension adjusted to about 104 conidia/ ml. RESULTS AND DISCUSSION Benomyl-resistant strains of the leaf spot fungus were detected in a sour cherry orchard in 1975, in another in 1976, and in three sweet and four sour cherry orchards in 1979. One of the sour cherry orchards identified in 1979 was a fungicide research orchard on the Michigan State University campus. Resistant strains were also detected on sour and sweet cherries in a fruit tree nursery in 1979. Most of the orchards were heavily defoliated when the samples were taken and a high proportion of the leaf disks from these orchards yielded resistant spores. Sites with resistant strains occurred in each of the important cherrygrowing areas of the state (Fig. 1). Five of the sites were in the counties surrounding Traverse City, where 78% of the sweet cherries and 49.5% of the sour cherries are grown in Michigan (1). In two cases, resistance was detected on adjacent farms, but the remaining locations were well separated from one another and the benomyl-resistant strains were considered geographically distinct. In 1975, five single-spore isolates of putative resistant strains from one orchard were tested by using the disk assay, and no inhibition zones developed on media amended with benomyl at rates of 0.1, 1.0, 10,20,40, 60, 80, 100,200,400, and 600 Ag/ ml. Small zones of inhibition were noted with three isolates at 800 Ag/ ml and with all isolates at 1,000 Ag/ ml. Inhibition zones were produced with six sensitive isolates at 1.0 4g/ ml. No inhibition zones were noted at 1,000 Ag/ ml with two resistant isolates from the orchard in 1976, although inhibited zones were noted at 1.0 lg/ml benomyl with three sensitive isolates from other orchards. All resistant strains sporulated in the presence of benomyl on artificial media. In limited greenhouse trials, resistant isolates infected cherry leaves sprayed with benomyl 50% a.i. WP at 226.8 Fig. 1. Geographic distribution of benomylresistant Coccomyces hiemalis in Michigan. All but two locations were detected in 1979. (A = site of benomyl-resistant cherry leaf spot.) Plant Disease/August 1980 767 g/ 378.5 L of water, but sensitive isolates were controlled. In a field trial in 1976, benomyl 50% a.i. WP at 226.8 g/378.5 L failed to control leaf spot under light disease pressure (4), and 97% of the leaf disks from benomyl-sprayed trees yielded resistant conidia. Isolates resistant to benomyl were also resistant to carbendazim and thiophanate-methyl in vitro, which agrees with most reports of benomyl-resistant fungi. Fungicide concentrations to 1,000 ug/ ml benomyl, carbendazim, and thiophanate-methyl did not result in inhibition zones with Table 1. Pattern of benomyl use in cherry orchards where resistant strains of Coccomyces hiemalis were detected Total fungicide Benomyl 50% a.i. WP Orcharda applications Application Rateb Fungicides (and rates) Year (no.) (no.) (g) combined with benomyl b Sour cherry, no. 1 1975 1974 1973 1972 Sour cherry, no. 2' 1979 1978 1977 1976 1975 Before 1975 Sour cherry, no. 3 1979 1978
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TL;DR: Although 17 accessions of this forage legume, including commercial cultivars Cunningham and Peru, were moderately to highly susceptible to the pathogen, potential resistance was found in six accession of L. leucocephala and severalAccessions of five other Leucaena spp.
Abstract: LENNE, J. M. 1980. Camptomeris leaf spot on Leucaena spp. in Colombia. Plant Disease 64: 414-415. Camptomeris leucaenae severely defoliated experimental plantings of Leucaena leucocephala in Colombia. Although 17 accessions of this forage legume, including commercial cultivars Cunningham and Peru, were moderately to highly susceptible to the pathogen, potential resistance was found in six accessions of L. leucocephala and several accessions of five other Leucaena spp. This is the first record of C. leucaenae on Leucaena spp. in Colombia and the first report of damage caused by the fungus. Leucaena leucocephala (= L. glauca) is a tree legume native to the subhumid and humid tropics of Central America (5). Its value as a high-quality protein forage in association with grasses is being investigated in tropical Latin America (2), Australia, Hawaii, and other
TL;DR: Six lucerne cultivars were assessed for the Incidence of leaf spot on autumn growth in flood irrigation trials and ‘Saranac’ and “WL318” were the most tolerant, ‘Pioneer 521” and � ‘Wairau’ were moderately tolerant, but ‘AS 13R‚ and ‚Washoe‚ were highly susceptible.
Abstract: Six lucerne cultivars were assessed for the Incidence of leaf spot on autumn growth in flood irrigation trials. Common leaf spot, caused by Pseudopeziza medicaginis, and the most prevalent disease, and cultivars were divided into 3 groups depending on their resistance to it. ‘Saranac’ and ‘WL318’ were the most tolerant, ‘Pioneer 521’ and ‘Wairau’ were moderately tolerant, but ‘AS 13R’ and ‘Washoe’ were highly susceptible. Yellow leaf blotch and Stemphylium leaf spot were also assessed, but these diseases were of minor significance.
Journal Article•
TL;DR: Results depict that antibiotics produced by competing microfungi caused the phenomenon of mycostasis on the leaf surfaces.
Abstract: The effect of fungal staling growth products on leaf-inhabiting microfungi, with special reference to a leaf spot pathogenPestalotiopsis funerea Desm. ofEucalyptus globulus Labill. was studied. Results depict that antibiotics produced by competing microfungi caused the phenomenon of mycostasis on the leaf surfaces.
TL;DR: This is the first record of the disease, brown spot, for New Zealand, and the pathogen can be differentiated from other pseudomonads isolated from diseased bean leaves by a serological test and peach seedling inoculation.
Abstract: The pathogen of a bacterial leaf spot disease of bean (Phaseolus vulgaris L.) was identified as Pseudomonas syringae pv. syringae van Hall 1902.This is the first record of the disease, brown spot, for New Zealand. The pathogen can be differentiated from other pseudomonads isolated from diseased bean leaves by a serological test and peach seedling inoculation.
TL;DR: In dense plantings in the greenhouse, bacterial leaf spot of zinnia caused by Xanthomonas nigromaculans f.
Abstract: STRIDER, D L 1980 Control of bacterial leaf spot of zinnia with captan Plant Disease 64:920922 In dense plantings in the greenhouse, bacterial leaf spot of zinnia caused by Xanthomonas nigromaculans f sp zinniae (= X campestris) was reduced from 100 to 2% diseased plants when infected seeds were treated with captan Control was best using a 30-min seed-soak in 360 g ai captan per liter of water containing the wetting agent Tween 80 Dry treatment with captan 50 WP was not as effective, but the percent diseased plants was reduced from 100 to 124 In plant beds outside the greenhouse, spread was reduced by weekly foliar applications of captan (48 g ai / L of water) Streptomycin was effective but moderately phytotoxic In vitro sensitivity of Xanthomonas nigromaculans (Takimoto) Dowson f sp zinniae Hopkins and Dowson (= X campestris (Pammel) Dowson [2]), the cause of bacterial spot of zinnia, to captan was recently reported (19) That captan has utility in control of bacterial spot of zinnia as a seed treatment and as a foliar spray was hypothesized because 250 Ag/ml ai captan in nutrient agar prevented growth of X nigromaculans f sp zinniae (19) and because captan is commonly used at a much higher rate (1,230 Ag/ml ai) as a foliar spray for control of many fungal diseases (14) Since its development in the early 1940s, captan has been a useful and versatile fungicide (14), but its activity against X nigromaculans f sp zinniae was surprising However, a review of the literature revealed several reports on the efficacy of captan as a bactericide (4-9,11,12,15,16,22) In 1960 Diener and Carlton (7) reported that captan appeared to increase the effectiveness of dodine for bacterial spot control of peach caused by Xanthomonas pruni Daines (4-6) also found that captan reduced the incidence of bacterial spot of peach Shekharvat and Srivastava (15) reported that a 005% captan seed-soak reduced seedling infection of rice by Xanthomonas translucens f sp oryzae A preinoculation spray of seedlings gave reduction of the disease equal to that given by a streptomycin-chlorotetracycline treat
TL;DR: Treatment by Sivanesan and Gibson (1976), that combined all species of Entomosporium into one species E. mespili (DC. ex Duby) Sacc, was supported through the investigation of many exsiccati and fresh specimens.
Abstract: Treatment by Sivanesan and Gibson (1976), that combined all species of Entomosporium into one species E. mespili (DC. ex Duby) Sacc, was supported through the investigation of many exsiccati and fresh specimens.Morphologically, all specimens and isolates of Entomosporium, which had been differentiated into 4 species, could not be divided into clearly separated groups.The fungus has been recorded on 50 host species and the disease is widespread throughout the world.
TL;DR: Antibiotics, besides alteration in pH, and nutrient impoverishment of the staling growth products, may play a major role in the mycostasis phenomenon leading to colonization of staled agar by phyllosphere microfungi.
Abstract: Pestalotiopsis funerea Desm. causing leaf spot ofEucalyptus globulus Labill. failed to coloniz strongly staled agar discs of phyllosphere inocula. Antibiotics, besides alteration in pH, and nutrient impoverishment of the staling growth products, may play a major role in the mycostasis phenomenon leading to colonization of staled agar by phyllosphere microfungi.
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TL;DR: Regardless of the kind of the apple orchards whether received various fungicides application or not Rovral exhibited the most efficient inhibitory effect on the sporulation of Alternaria mali with the spotted leaf disks at the recommended dose at the lower or the higher doses.
Abstract: Regardless of the kind of the apple orchards whether received various fungicides application or not Rovral exhibited the most efficient inhibitory effect on the sporulation of Alternaria mali with the spotted leaf disks at the recommended dose as well as the lower or the higher doses When applied at the recommended doses of Antracol, Dithane M-45, and Dikar, respectively, these fungicides showed complete inhibitory effects on the sporulation At the lower levels of application, they allowed the sporulation of 10,000 to 25,000 conidia/ml Polyoxin and Difolatan, when applied on the leaf disks from the orchard that had received the fungicides application, exhibited low effects allowing the sporulation of around 20,000 conidia/ml On the leaf disks from the orchard that had received no fungicide application, however, both fungicides showed relatively high inhibitory effects of the sporulation The inhibitory effects of Captan, Dakonil, and Spat on the sporulation were lower than those of the aforementioned fungicides Bayleton was the least effective among the fungicides used in the present investigation Benlate showed promoting effect on the sporulation of the apple leaf spot fungus rather tan inhibiting