Showing papers on "Leaf spot published in 1969"

Curvularia leaf spot of maize

Abstract: The causal agent of a leaf spot of maize in S.W. Nigeria is identified as Curvularia pallescens and its pathogenicity to maize is demonstrated by inoculation experiments. The symptoms are described and contrasted with those of the other locally abundant leaf spot, caused by Helminthosporium maydis .

Spraying for leaf spot and liming increase yam (dioscorea alata l.) yield

Abstract: When yams were not sprayed to control leaf spot disease caused by Colletotrichum sp. essentially no yams were produced regardless of lime rates. When leaf spot was controlled by spraying, yam yields increased with increasing lime rates up to 36 t/ha, the highest level tested. The combined effect of spraying and liming increased yields from 1.4 to 30.6 t/ha. Yields were increased threefold when Al saturation of the soil exchange capacity was decreased from 37% to 0 by liming. Yields were decreased by 30% when Al saturation of the soil was increased only from 0 to 9%, a level at which most crops will not show a response to Al. This decrease illustrates the extreme sensitivity of yams to exchangeable Al in the soil. Composition of the leaves 6 months after planting was affected neither by lime rates nor spraying. The pH, Al saturation percentage of the soil exchangeable capacity, and lime rates applied were closely correlated with yam yields.

Reaction of Dry Bean Genotypes to Natural Infection of Foliar Diseases in the Dominican Republic.

Abstract: Seventeen dry bean genotypes were tested in 18 field trials on small farms and experiment stations in the Dominican Republic in the 1981-1982 growing season, and 20 bean genotypes were tested in 10 trials in the 1982-1983 growing season to measure the reaction of promising dry bean genotypes and standard cultivars from the Dominican Republic to natural infection of foliar diseases, and to determine the frequency and intensity of foliar diseases when dry beans are generally grown in the Dominican Republic Bacterial blight [ Xanthomonas campestris pr phaseoli (Smith) Dye] was the most serious disease during the September plantings Rust [ Uromyces phaseoli (Reben) Wint] was the most prevalent disease when beans were planted in January, which is a drier month There was little difference among the dry bean genotypes in reaction to bacterial blight All of the genotypes developed at least a moderate level of infection of bacterial blight following the September plantings However, several genotypes expressed high levels of resistance to rust Among the standard red mottled cultivars, Pompadour developed the lowest level of rust infection Angular leaf spot ( lsariopsis griseola Sacc) and chaetoseptoria leaf spot ( Chaetoseptoria wellmanii Stevenson) also were observed in several experiments One genotype, 5B-42-2-1, expressed a low level of infection to angular leaf spot having an average score of 15, whereas all genotypes were found to be susceptible to chaetoseptoria leaf spot

Effect of fungicide on disease incidence and yield of bean (Phaseolus vulgaris L.) infected with Isariopsis griseola Sacc. and Ascochyta phaseolorum Sacc.

Abstract: Two foliar diseases of beans, Phaseolus vulgaris L., namely angular leaf spot and ascochyta leaf spot, caused by Isariopsis griseola and Ascochyta phaseolorum , respectively, were effectively controlled with chemicals. Biweekly applications of mancozeb and chlorothalonil (1.12, 2.48 and 4.48 kg/ ha) effectively protected the foliage of bean cultivars Bonita and Naranjito against attacks by both pathogens. Cultivar Bonita responded better to treatments than cv. Naranjito in terms of yield. Some dosages of mancozeb and chlorothalonil increased yield of cv. Bonita affected by angular leaf spot. Yield increases in plots treated with benomyl increased only when the highest rate of this chemical was used. Even at the lowest dosages, the three chemicals tested increased yield in cv. Bonita affected by the ascochyta leaf spot disease.

Bacterial leaf spot of pigeon pea in Puerto Rico

Abstract: A leaf spot bacterium was isolated from diseased leaves of Kaki pigeon pea ( Cajanus cajan ). The lesions were minute, necrotic and surrounded by a yellow halo, eventually coalescing to form larger area approximately 1 to 2 mm. in diameter. The bacterium is a Gram-negative bacillus, motile, forming butter-yellow, mucoid, and shiny colonies. The bacterium hydrolyzes gelatine, starch, fats, casein, and esculin. It also acidifies glucose, sucrose, and maltose but not salicin, and uses citrate and malonate. When artificially inoculated on healthy pigeon pea, bean ( Phaseolus vulgaris) and pea ( Pisum sativum ), the characteristic lesions were reproduced in their original host only. On the basis of its biochemical characteristics and confirmation by recovery from artificially inoculated diseased pigeon pea leaves, the organism was identified as Xanthomonas campestris pv. cajani . This is the first record of the disease in Puerto Rico.

Diseases caused by Pseudomonas spp in some cultivars in Puerto Rico—an updating

Abstract: A revision of the species of Pseudomonas affecting cultivars of economic importance in Puerto Rico is presented The pathogen has been isolated from various vegetables, fruits and ornamentals Studies of the isolates include affected plants, cultural characters, hypersensitivity reaction and other pathogenicity tests Some saprophytic Pseudomonas spp producing leaf spot disease in some cultivars are reported herein for the first time

First report of algal leaf spot caused by cephaleuros virescens kunze on longan trees in puerto rico

Abstract: FIRST REPORT OF ALGAL LEAF SPOT CAUSED BY CEPHALEUROS VIRESCENS KUNZE ON LONGAN TREES IN PUERTO RICO