Showing papers on "Leaf spot published in 1995"
01 Jan 1995
TL;DR: Simple and effective field screening methods to identify genotypes with resistance toRust and late leaf spot are described, and several reliable sources of resistance to rust and/or late leafspot were identified.
Abstract: Rust and late leaf spot are the most serious fungal diseases of groundnut worldwide, and can cause severe yield losses,
particularly when they occur together. This Bulletin describes simple and effective field screening methods to identify
genotypes with resistance to these diseases. Production of inoculum, sowing and inoculation of test genotypes, and disease
assessment in the field, using a 1-9 scale, are discussed. These methods were used dUring 1977-89 to evaluate ICRISAT's
world collection of over 12 000 groundnut accessions. Several reliable sources of resistance to rust and/or late leaf spot
were identified, and are listed here-124 lines resistant to rust, 54 lines resistant to late leaf spot, and 29 lines with
combined resistance. An extensive bibliography is also presented, for those who require more detailed information on
specific aspects of the diseases.
157 citations
01 Jan 1995
TL;DR: In this paper, the authors describe simple and effective field screening methods to identify groundnut genotypes with resistance to groundnut fungal diseases such as rust and late leaf spot, using a 1-9 scale.
Abstract: Rust and late leaf spot are the most serious fungal diseases of groundnut worldwide, and can cause severe yield losses,
particularly when they occur together. This Bulletin describes simple and effective field screening methods to identify
genotypes with resistance to these diseases. Production of inoculum, sowing and inoculation of test genotypes, and disease
assessment in the field, using a 1-9 scale, are discussed. These methods were used dUring 1977-89 to evaluate ICRISAT's
world collection of over 12 000 groundnut accessions. Several reliable sources of resistance to rust and/or late leaf spot
were identified, and are listed here-124 lines resistant to rust, 54 lines resistant to late leaf spot, and 29 lines with
combined resistance. An extensive bibliography is also presented, for those who require more detailed information on
specific aspects of the diseases.
108 citations
TL;DR: It is demonstrated that an epidemic of onion leaf spot largely depends on the rate of inoculum production inside a crop, and suppression of sporulation on necrotic leaf tissue is a valid control strategy that could be applied by using sporulation suppressing antagonists.
Abstract: In this study, the hypothesis was tested that removal of substrate for sporulation ofBotrytis spp. may lead to a retardation of an epidemic if the majority of the inoculum is produced inside the treated crop. Suppression of sporulation ofBotrytis spp. could be an attractive option for biological control ofBotrytis leaf spot in onions. In a field experiment, necrotic leaf tissue was removed to simulate the effect of a biocontrol agent. By this means, the amount of substrate on whichBotrytis spp. sporulates was reduced. In the experiment, the spore load above the onion plots was significantly reduced and the epidemic of onion leaf spot was retarded. At the end of the growing season, the number of leaf lesions in the green leaf area was lower in plots with substrate removal than in control plots (0.6 and 1.1 cm−2, respectively). The results demonstrated that an epidemic of onion leaf spot largely depends on the rate of inoculum production inside a crop. Thus, suppression of sporulation on necrotic leaf tissue is a valid control strategy that could be applied by using sporulation suppressing antagonists.
56 citations
TL;DR: Management strategies aimed at decreasing levels of inoculum during early infection cycles are suggested as an effective means of reducing the severity of gray leaf spot disease.
Abstract: The epidemiology of gray leaf spot disease (GLS) on field corn (Zea mays) was studied following artificial inoculation with the fungus, Cercaspara zeae-maydis Studies were based on relative differences in selected infection cycle components between a susceptible and a moderately resistant corn hybrid Area under the disease progress curve, apparent infection rate, number of lesions, and sporulation capacity were lower and latent period was longer on the moderately resistant hybrid than on the susceptible hybrid Based on comparisons of disease progress curves, infection cycle components, and rainfall patterns, it is postulated that rainfall and sporulation during early infection cycles have a significant effect on development of GLS Management strategies aimed at decreasing levels of inoculum during early infection cycles are suggested as an effective means of reducing the severity of GLS
42 citations
TL;DR: Three of five sugarbeet fields from two districts in Minnesota had unacceptable levels of Cercospora leaf spot after being treated with the maximum label amount of triphenyltin hydroxide (TPTH) in 1994.
Abstract: Three of five sugarbeet fields from two districts in Minnesota had unacceptable levels of Cercospora leaf spot after being treated with the maximum label amount of triphenyltin hydroxide (TPTH) in 1994. Strains of the fungus with varied levels of tolerance to TPTH were recovered from leaf spots. Mancozeb was effective against the tolerant strains. Strains with resistance to thiophanate methyl also were recovered.
40 citations
TL;DR: A widespread and damaging outbreak of a leaf spot disease of lettuce occurred in the 1992-93 winter vegetable season in southern Florida and disease reactions generally were more severe in cos and butterhead lettuce than in crisphead.
Abstract: A widespread and damaging outbreak of a leaf spot disease of lettuce occurred in the 1992-93 winter vegetable season in southern Florida. Individual leaf lesions were dark brown to black, water-soaked, and greasy in appearance. A yellow-pigmented bacterium was consistently isolated. All 1992-93 lettuce strains and reference strains produced symptoms in greenhouse test plants that were identical to those seen in the field. Disease reactions generally were more severe in cos and butterhead lettuce than in crisphead. Strains were gram-negative rods, and negative for glucose fermentation, nitrate reduction, urease production, and utilization of asparagine as a sole source of carbon and nitrogen. Aesculin was hydrolyzed, gelatin was liquefied, and proteolysis occurred in litmus milk. Cellular fatty acid profiles matched well to library database strains of Xanthomonas campestris pv. vitians.
36 citations
TL;DR: Experiments were done under controlled environment and glasshouse conditions to study the effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brassicae) on oilseed rape (Brassica napus).
Abstract: Experiments were done under controlled environment and glasshouse conditions to study the effects of inoculum concentration, leaf age and wetness period on the development of dark leaf and pod spot (Alternaria brassicae) on oilseed rape (Brassica napus). On leaves of potted oilseed rape plants (cv. Bienvenu) inoculated with A. brassicae conidial suspensions, the severity (number of lesions cm(-2)) of dark leaf spot increased as inoculum concentration increased from 80 to 660 Spores ml(-1) and as leaf age increased from 4 to 14 days. On pods on detached racemes of spring oilseed rape (cv. Starlight), the incidence of dark pod spot (% of pods diseased) increased as inoculum concentration increased from 80 to 10(4) spores ml(-1). Increasing inoculum concentration above 10(4) spores ml(-1) did not increase the incidence but did increase the severity of dark pod spot. A minimum wetness period of 4 h was needed for infection of oilseed rape leaves (cv. Envol) by A. brassicae at 18 degrees C and disease severity increased with increasing wetness period up to 12 h. The length of dry interruptions after 3-8 h of initial wetness affected the severity of dark leaf spot. A second wetness period increased the severity of dark leaf spot if the dry interruption was less than or equal to 6 h and if the first wetness period was less than or equal to 8 h. The incubation period of A. brassicae decreased from 3.5 to 2.5 days as inoculum concentration increased from 80 to 660 spores ml(-1) on leaves (cv. Bienvenu) at 17-25 degrees C and from 3.8 to 1.0 day as inoculum concentration increased from 80 to greater than or equal to 2 x 10(3) spores ml(-1) on pods (cv. Starlight) at 18 degrees C.
36 citations
TL;DR: Asymptotic curvilinear reductions in late leaf spot and area under the disease progress curve were observed with increasing rates of cyproconazole within all levels of chlorothalonil.
Abstract: Field tests were conducted in Plains, Georgia, USA, in 1990 and 1991 and in Tifton, Georgia, in 1991 to determine the effects of cyproconazole (0, 123, 246, 493, 739 and 987 g/ha) and chlorothalonil (0, 210, 420 and 630 g/ha), applied alone and in tank mixes, on late leaf spot (Cercosporidium personatum [Mycosphaerella berkeleyi]), southern stem rot (Sclerotium rolfsii [Corticium rolfsii]) and groundnut yields Asymptotic curvilinear reductions in late leaf spot and area under the disease progress curve were observed with increasing rates of cyproconazole within all levels of chlorothalonil Late leaf spot rating decreased linearly with increasing rates of chlorothalonil within cyproconazole rates of 246 g/ha or lower in 1990 and 493 g/ha or lower in 1991 Quadratic curvilinear reductions in the incidence of stem rot with increasing rates of cyproconazole were observed in both years Chlorothalonil had no effect on incidence of stem rot Yield increased linearly or curvilinearly with increasing rates of cyproconazole, with yields converging with the higher rates of cyproconazole within all rates of chlorothalonil In 1990 and 1991, increases in yield with increasing rates of chlorothalonil diminished as rates of cyproconazole increased When applied with 420 or 630 g/ha of chlorothalonil, rates of cyproconazole required to provide adequate leaf spot control were much lower than rates required for control of stem rot control in fields with moderate to heavy disease incidence In field experiments conducted in Tifton in 1992 and 1993, tank mixes of 34 g/ha of cyproconazole and 420 g/ha of chlorothalonil provided control of leaf spot that was superior to that obtained with the standard recommended rate (126 kg/ha) of chlorothalonil alone Incidence of stem rot and pod yields were similar for those 2 treatments
34 citations
TL;DR: A survey of Chinese-elm hybrids revealed that the same gene is likely to confer a high level of resistance to black leaf spot in interspecific elm hybrids, although other genetic factors may also be involved in the determination of a disease phenotype.
Abstract: Black leaf spot (Stegophora ulmea) is a common foliage disease on Chinese (Ulmus parvifolia) and Siberian elms (U. pumila), two species which have been widely used as sources of Dutch-elm disease-resistance genes for interspecific elm hybrids. A dominant gene controlling resistance to black leaf spot was identified in a population derived from self-pollination of a single U. parvifolia tree. Using RAPD markers, in combination with bulked segregant analysis, we have identified three markers linked to this resistance gene. A survey of Chinese-elm hybrids revealed that the same gene is likely to confer a high level of resistance to black leaf spot in interspecific elm hybrids, although other genetic factors may also be involved in the determination of a disease phenotype.
31 citations
TL;DR: The AU-Pnuts advisory can be used to reduce the number of leaf spot fungicide applications and achieve disease control and yield similar to that with peanuts sprayed on the 14-day schedule.
Abstract: The AU-Pnuts advisory was developed to schedule both the initial and subsequent fungicide applications for control of early (Cercospora arachidicola) and late (Cercosporidium personatum) leaf spots of peanut. The advisory uses the number of days with precipitation greater than 2.5 mm and National Weather Service precipitation probabilities to predict periods favorable for development of early and late leaf spot. Field experiments were conducted from 1989 through 1992 to assess the impact of the AU-Pnuts advisory on early and late leaf spot incidence and yield of Florunner peanut. Use of the AU-Pnuts advisory resulted in a 4-year average of 1.25 fewer fungicide applications than the conventional 14-day schedule. Leaf spot disease control and yields were equivalent to or better than the 14-day schedule. The AU-Pnuts advisory can be used to reduce the number of leaf spot fungicide applications and achieve disease control and yield similar to that with peanuts sprayed on the 14-day schedule.
29 citations
Journal Article•
TL;DR: Host resistance was very effective: in the most resistant cultivars the infection rate was 35% less than that of the susceptible one, and in the least resistant cultivar it was 19%.
Abstract: The effect of nine sugarbeet cultivars with different known levels of resistance in reducing the apparent infection rate of Cercospora leaf spot epidemics compared to a susceptible cultivar, was studied at 18 locations during a three-year period. Host resistance was very effective: in the most resistant cultivars the infection rate, computed over a 30-day period during the progress of epidemics, was 35% less than that of the susceptible one, wheras in the least resistant cultivar it was 19%. Cultivar x environment (years and locations) interaction lead to wide variation in the magnitude of rate-reducing effect.
TL;DR: It is suggested that fungicide spraying initiated at R1 and followed up at R3 is most effective in frogeye leaf spot control and can also result in higher grain yields, than applications made earlier or later in the season.
Abstract: Soybean cultivar Samsoy 1, and the breeding lines TGx 849-313D and TGx 996-26E, grown in a field with a heavy epidemic of frogeye leaf spot caused byCercospora sojina, were treated with double foliar applications of the fungicide benomyl. The treatments were made using four application schedules at six different growth stages, starting from V3 (fully developed leaves, beginning with trifoliate nodes) to R5 (beginning seed_, to determine the effect of the fungucide timing on frogeye leaf spot severity, soybean grain yield and grain quality. Generally, applications at R1 (beginning bloom) and R3 (beginning pod) significantly (P<-0.05) reduced disease severity in the 2 susceptible genotypes, Samsoy 1 and TGx 849-313D. Plot yields of these genotypes were also significantly greater than the untreated controls when the fungicide applications were made at R1 and R3. There was no significant difference in diseave severity or grain yield, between the untreated control and the different times of application, on the resistant genotype TGx 996-26E. Improved seed germination and lower levels of seed infection byC. sojina occurred for all fungicide timings in the susceptible genotypes. The results suggest that fungicide spraying initiated at R1 and followed up at R3 is most effective in frogeye leaf spot control and can also result in higher grain yields, than applications made earlier or later in the season. Control of frogeye leaf spot, however, is best achieved by growing resistant cultivars.
TL;DR: Latent period and maximum percentage of lesions that sporulated were the components most highly correlated with late leaf spot disease development, and using either of these two components to evaluate peanut genotypes for resistance toLate leaf spot may facilitate more rapid selection of lines with improved levels of rate-reducing resistance.
Abstract: Components of partial resistance to late leaf spot (Cercosporidium personatum) and disease progression on 14 peanut genotypes were quantified in field experiments at Marianna, Florida, during 1988 and 1989. The resistance components measured were 1) incubation period, 2) latent period, 3) maximum percentage of lesions that sporulated, 4) lesion size, 5) lesion number, 7) degree of sporulation, and 7) percent necrotic area. Lower area under the disease progress curve (AUDPC) values, reduced apparent infection rates, and lower end-of-season disease levels were observed on genotypes UF81206-1, PI 261893, US29-b3-B, and US202-b2 compared to other genotypes in the study. Both apparent infection rate and AUDPC values were highly correlated with latent period (r = −0.68 to −0.79, P ≤ 0.01) and maximum percentage of lesions that sporulated (r = 0.72-0.81, P ≤ 0.01). Latent period and maximum percentage of lesions that sporulated were the components most highly correlated with late leaf spot disease development, and these two components were highly correlated with one another (r = -0.84). Using either of these two components to evaluate peanut genotypes for resistance to late leaf spot may facilitate more rapid selection of lines with improved levels of rate-reducing resistance
TL;DR: In field experiments, light leaf spot always developed on oilseed rape with a leaf wetness duration of 48 h after inoculation in both 1990/1991 and 1991/1992, but the percentage leaf area affected was less on plants placed in an oil seed rape crop than on those placed in a glasshouse.
Abstract: In controlled environment experiments to study early development of light leaf spot, lesions developed with leaf wetness durations of 16 to 48 h after inoculation of oilseed rape with conidial suspensions of Pyrenopeziza brassicae at 12 or 18°C, but not with leaf wetness durations of 0 to 13h. The incubation period was 21 to 22 days at 12°C and 14 to 18 days at 18°C for leaf wetness durations of 16 to 48 h. The latent period was 21 to 23 days at 12°C and 18 to 19 days at 18°C, and the total number of lesions increased with increasing leaf wetness duration at both temperatures. In field experiments, light leaf spot always developed on oilseed rape with a leaf wetness duration of 48 h after inoculation in both 1990/1991 and 1991/1992, but the percentage leaf area affected was less on plants placed in an oilseed rape crop than on those placed in a glasshouse. Plants moved to an oilseed rape crop immediately after inoculation nearly always developed light leaf spot symptoms when they were inoculated between 19 October 1990 and 1 March 1991 or between 27 September 1991 and 14 February 1992, but plants inoculated between 31 August and 16 October 1990 or on 20 September 1991, when estimated leaf wetness duration was less than 16 h for several days after they were placed in crops, did not develop symptoms. The latent period of light leaf spot on plants transferred to the oilseed rape crop was 15 to 40 days, and there was an approximately linear relationship between 1 (latent period) and mean temperature during this period. The accumulated temperature during the latent period ranged from c. 150 to 250 day-degrees. The severity of lesions on these plants increased with increasing temperature from 5 to 15°C.
TL;DR: Ten Trichoderma isolates studied under greenhouse conditions as potential agents for biocontrol of yam leaf spot, caused by Curvularia eragrostidis demonstrated high efficiency of disease control.
Abstract: TenTrichoderma isolates were studied under greenhouse conditions as potential agents for biocontrol of yam leaf spot, caused byCurvularia eragrostidis. TheTrichoderma isolates demonstrated high efficiency of disease control. Application of the antagonists on the same day asC. eragrostidis inoculation showed the best results. One isolate achieved 75 percent disease severity reduction. The survival of theTrichoderma isolates decreased after its application on the phylloplane with values of 57 and 41 percent at the 49th day, in the absence and presence of the phytopathogen respectively. The antagonism persisted well againstC. eragrostidis, the TN1 isolate praises 89 percent.
TL;DR: The findings suggested that a low incidence of Septoria leaf spot may develop under unfavorable conditions and that leaf abrasion may allow spores to infect in the absence of dew.
Abstract: In order to determine the effects of spore density, leaf age, dew period, and temperature on the susceptibility of tomato to Septoria lycopersici, growth chamber studies were conducted. Depending on the leaf area, 3-5 ml of water containing 10 2 , 10 3 , 10 4 , 10 5 , and 10 6 spores per milliliter were brushed onto the third true leaf up to the seventh true leaf. The log of the disease severity (lesions per square centimeter of leaf) was linearly correlated with the log of the inoculum density (spores per square centimeter of leaf). Older leaves were more susceptible than younger leaves to Septoria leaf spot when inoculum densities were high (10 4 spores per square centimeter of leaf), but younger and older leaves were uniformly susceptible when inoculum densities were low (10 1 to 10 2 spores per square centimeter of leaf). When older leaves were brush inoculated (104 spores per square centimeter of leaf), the number of lesions that developed was highest at temperatures between 20 and 25 C, but lesions still developed at 10 C. When brush-inoculated leaves were incubated for 10 days at 50-6O% relative humidity without any dew period, the number of lesions that developed did not significantly differ from inoculated leaves that had received 16 hr of dew. Disease severity increased when the dew period extended beyond 20 hr. When leaves were spray inoculated, no lesions developed when dew was absent, but lesions did develop on leaves that were given 24 hr of dew. Our findings suggested that a low incidence of Septoria leaf spot may develop under unfavorable conditions and that leaf abrasion may allow spores to infect in the absence of dew
Journal Article•
TL;DR: The responses to temperature for lesion severity and incubation and latent periods appeared to be approximately linear over the temperature range 5-15 degrees C and could be quantified using linear regression analysis.
Abstract: The effects of temperature on the development of light leaf spot (Pyrenopeziza brassicae) on winter oilseed rape were investigated in controlled-environment experiments. The proportion of conidia which germinated on leaves, the growth rate of germ tubes, the severity of light leaf spot and the production of conidia increased with increasing temperature from 5 to 15 degrees C. The time to 50% germination of conidia and the incubation and latent periods of light leaf spot lesions decreased when temperature increased from 5 to 15 degrees C. At 20 degrees C, however, light leaf spot severity and production of conidia were less and the incubation and latent periods were longer than at 15 degrees C. There were differences between P. brassicae isolates and oilseed rape cultivars in the severity of light leaf spot, the production of conidia and the length of the incubation period but not in the length of the latent period. The responses to temperature for lesion severity and incubation and latent periods appeared to be approximately linear over the temperature range 5-15 degrees C and could be quantified using linear regression analysis.
TL;DR: In this article, the level of susceptibility was evaluated based on maximum disease severity and area under the disease progress curve (AUDPC), and 23 strawberry (Fragaria ×ananassa Duchesne) cultivars were ranked based on AUDPC and grouped according to their susceptibility.
Abstract: Seventeen strawberry (Fragaria ×ananassa Duchesne) cultivars and six selec- tions were tested under greenhouse conditions for susceptibility to leaf spot induced by Mycosphaerella fragariae (Tul.) Lindau. The level of susceptibility was evaluated based on maximum disease severity and area under the disease progress curve (AUDPC). The 23 genotypes were ranked based on AUDPC and grouped according to their susceptibility. Cluster analysis for AUDPC gave four groups corresponding to low, moderate, high, and very high susceptibility to leaf spot. 'Annapolis', 'Chambly', 'Glooscap', 'Redcoat', and 'Veestar' consistently showed a low level of susceptibility. The selections SJ89700-1 and SJ8518-11 and 'Tribute' showed a very high level of susceptibility, and the remaining cultivars were grouped as either moderately or highly susceptible.
TL;DR: The Septoria sp.
Abstract: Pathogenicity tests with a Septoria sp. isolated from Lantana camara from Ecuador showed aggressiveness to four L camara selections from Hawaii forests. The initial symptoms of the disease on inoculated leaves were chlorotic spots that appear within 2 weeks, becoming distinctly angular necrotic lesions in 4 weeks, inducing leaf chlorosis and defoliation 6 weeks after inoculation. Inoculum applied at 1 x 10 6 conidia per ml in 2% sucrose-0.5% gelatin solution produced an average of 87 lesions per leaf. Ornamental hybrids of L. camara x L. montevidensis also were susceptible, but these plants had significantly fewer lesions. All selections of L. montevidensis tested were immune. This Septoria sp. from Ecuador is the first pathogen found to be virulent on bush lantana, the most serious ecological threat to Kauai's forest, and its release is presumed to be an effective biocontrol agent for this weed.
TL;DR: It is confirmed that rain is a primary mechanism for spore dissemination and an important factor contributing to the development of Septoria leaf spot epidemics in tomatoes.
Abstract: Tomato seedlings spaced 30 cm apart were placed 30-180 cm from an inoculum source in the field for 24-hr periods on five rain dates and five non-rain dates. The mean number of lesions per leaf on plants exposed on rain dates ranged from 70 to 1,680, whereas only 0.0-0.46 lesions per leaf developed on plants exposed on non-rain dates. The mean number of lesions per leaf was linearly related to millimeters of rainfall during exposure periods (b 0 = −224, b 1 = 528, R 2 = 0.86, P < 0.0001). Percent defoliation within rows of tomato plants increased at the apparent infection rate of 0.282 units per day following spray inoculation of the center plant in each row. The study confirms that rain is a primary mechanism for spore dissemination and an important factor contributing to the development of Septoria leaf spot epidemics in tomatoes
30 Nov 1995
TL;DR: Reports of severe disease infestations are mostly from low lying areas and river bottoms where periods of leaf wetness and high relative humidity are long enough to favor the development and spread of the disease.
Abstract: Gray leaf spot of corn, caused by the fungus Cercospora zeae-maydis, has been known in the United States since 1924 when it was first reported in Illinois. Until the 1970’s, the disease was a minor pathogen with the exception of occasional outbreaks. With the increased use of reduced and notillage practices, gray leaf spot has become a very significant problem primarily in the more humid corn growing areas of the east and Midwest. The disease was first reported in Ohio in 1978 in parts of Pickaway, Ross, Pike, and Scioto counties in river bottom fields. Today, gray leaf spot can be found in all Ohio counties. Reports of severe disease infestations are mostly from low lying areas and river bottoms where periods of leaf wetness and high relative humidity are long enough to favor the development and spread of the disease. Potential yield losses from gray leaf spot generally range between 5 to 40 bushels/acre. Losses as high as 90-100% have been reported. This loss of leaf area results in a loss in sugar production, which translates into less grain. Extreme leaf damage leads to premature death of plants. Premature death lowers the value of the corn as silage and makes the corn more susceptible to stalk rot.
TL;DR: The cause of a leaf spot disease of several EucalyPTus species in Australia, India and Hawaii, U.S.A. is described as Cryptosporiopsis eucalypti sp.
TL;DR: In this article, a new species Mycosphaerella grac- ilis and its anamorph Pseudocercospora gracilis are described, the connection between the anamorph and teleomorph having been confirmed by cultural studies.
Abstract: Collections of Eucalyptus leaves throughout the forested regions of Indonesia have revealed three species of Mycosphaerella associated with prominent leaf spot symptoms. A new species Mycosphaerella grac- ilis and its anamorph Pseudocercospora gracilis are de? scribed here, the connection between the anamorph and teleomorph having been confirmed by cultural studies. Similarly, Stenella parkii is described as the anamorph of Mycosphaerella parkii, and an additional species of Mycosphaerella is recorded.
TL;DR: At those sites in which rust was the major disease, leaf and branch mortality were more pronounced than at Sites in which anthracnose or Cercospora leaf spot predominated, and the three variables soil pH, soil structure and temperature range allow a simple and satisfactory estimation of the epidemiological risks in a given plot.
Abstract: The simultaneous analysis of epidemiological and environmental variables could contribute to the determination of the main factors which govern the epidemic dynamics of diseases (i.e. rust, anthracnose and Cercospora leaf spot) in Coffea arabica. With this in mind, the condition of previously marked leaves in 29 plots. which were grouped in 11 different sites in New Caledonia. were surveyed monthly. In the same period, the environmental characteristics of the plots (soil type, climate, etc.)were determined.
Statistical analysis of these data revealed significant correlations between pathology and the environment. at the sites’ level (analysis of the mean site values) as well as at the plots' level (analysis of the deviations with the mean site value). The site effects predominated: at those sites in which rust was the major disease, leaf and branch mortality were more pronounced than at sites in which anthracnose or Cercospora leaf spot predominated. Rust was generally associated with soil pH values that were favourable for coffee tree development. with poor soil structure and with large temperature ranges. Within a site. plot exposure to sun and wind could enhance anthracnose and Cercospora leaf spot.
Finally, in New Caledonia the three variables soil pH, soil structure and temperature range allow a simple and satisfactory estimation of the epidemiological risks in a given plot.
Patent•
06 Jun 1995TL;DR: In this paper, the introgression of desired genetic material from one or more parent plants into progeny plants with precision and accuracy has been discussed for maize plants and a method of producing same, which are resistant to Gray Leaf Spot, referred to as GLS.
Abstract: This invention relates to maize plants and a method of producing same, which are resistant to Gray Leaf Spot which will hereinafter simply be referred to as GLS. More particularly this invention relates to the introgression in maize of identifiable genetic material capable of causing the plant to be resistant to GLS. Additionally, the present invention relates to the introgression of desired genetic material from one or more parent plants into progeny plants with precision and accuracy.
Journal Article•
TL;DR: The pooled data of these 2 years revealed that the extract of Adhatoda zeylanica was most effective in decreasing the severity of all the diseases followed by extracts of Azadirachta indica, Launaea coromandelica and Oxalis corniculata which significantly minimized powdery mildew and leaf rust.
Abstract: The effects of 10% alcoholic water extracts of fresh plant parts from 20 different species were investigated on the development of powdery mildew (Phyllactinia corylea) leaf spot (Pseudocercospora mori) and leaf rust (Cerotelium fici) of mulberry during 1992-93 and 1993-94 in West Bengal, India The pooled data of these 2 years revealed that the extract of Adhatoda zeylanica was most effective in decreasing the severity of all the diseases followed by extracts of Azadirachta indica, Launaea coromandelica [Lannea coromandelica] and Oxalis corniculata which significantly minimized powdery mildew and leaf rust, while those of Celosia argentia and Chromolaena odorata reduced leaf spot and leaf rust Extracts from several other plant species exhibitedan ability to reduce either leaf rust or powdery mildew disease
Patent•
30 May 1995TL;DR: A variety of Kentucky Bluegrass having a medium to high level of resistance to leaf spot, melting out disease, several rust diseases, dollar spot, powdery mildew and stripe smut; a desirable green color throughout the growing season; the ability to form a strong sod and a high quality dense persistent turf under a wide variety of environmental conditions; and has a medium level of seed yielding capacity as discussed by the authors.
Abstract: A variety of Kentucky Bluegrass having a medium to high level of resistance to leaf spot, melting out disease, several rust diseases, dollar spot, powdery mildew and stripe smut; a desirable green color throughout the growing season; the ability to form a strong sod and a high quality dense persistent turf under a wide variety of environmental conditions; and has a medium level of seed yielding capacity.
TL;DR: The AU-Pnuts advisory can be used to schedule fungicide applications for control of early and late leaf spot on Southern Runner peanut.
Abstract: The AU-Pnuts advisory was originally developed for peanut cultivars that are highly susceptible to early (Cercospora arachidicola) and late leaf spot (Cercosporidium personatum). The system uses a combination of recorded daily precipitation and National Weather Service precipitation probabilities to provide warnings for the need to apply fungicides. Field studies were conducted from 1989 through 1992 to evaluate modifications of the advisory for use on the late leaf spot resistant cultivar Southern Runner. The advisory system was modified by increasing the thresholds for both the initial and subsequent fungicide applications. Each modified advisory treatment was evaluated along with three other treatments: nonsprayed control, 14-day schedule, and 21-day schedule. Averaged over 1991 and 1992, the final version of the AU-Pnuts advisory saved 0.5 and 2.5 sprays compared with the 21-day and 14-day schedules, respectively. These timed fungicide applications controlled leaf spot as effectively as did the 21-day schedule. Yields were not significantly different between the advisory and either the 14-day or 21-day schedule. AU-Pnuts advisory can be used to schedule fungicide applications for control of early and late leaf spot on Southern Runner peanut.