scholarly journals Susceptibility of Strawberry Cultivars and Advanced Selections to Leaf Spot Caused by Mycosphaerella fragariae

HortScience ◽  
1995 ◽  
Vol 30 (3) ◽  
pp. 592-595 ◽  
Author(s):  
Nathalie Delhomez ◽  
Odile Carisse ◽  
Michel Lareau ◽  
Shahrokh Khanizadeh
Keyword(s):  
Cluster Analysis ◽  
Disease Severity ◽  
Leaf Spot ◽  
High Susceptibility ◽  
Disease Progress Curve ◽  
Progress Curve ◽  
High Level ◽  
Mycosphaerella Fragariae ◽  
Very High ◽  
Strawberry Cultivars

Seventeen strawberry (Fragaria ×ananassa Duchesne) cultivars and six selections 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.

scholarly journals Assessment of the Effects of Fertilizer Applications on Gray Leaf Spot and Yield in Maize

Plant Disease ◽  
2002 ◽  
Vol 86 (8) ◽  
pp. 859-866 ◽  
Author(s):  
P. M. Caldwell ◽  
J. M. J. Ward ◽  
N. Miles ◽  
M. D. Laing
Keyword(s):  
Grain Yield ◽  
Disease Severity ◽  
Leaf Spot ◽  
Gray Leaf Spot ◽  
Small Scale ◽  
Grain Yields ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve ◽  
Maize Grain

The effects of the application of 0, 60, and 120 kg N ha-1 and of 0, 25, 50, and 150 kg K ha-1 on final disease severity, standardized area under disease progress curve, and grain yield were investigated at Cedara, South Africa, on a maize (Zea mays) hybrid susceptible to gray leaf spot (GLS), caused by Cercospora zeae-maydis. The trial was a randomized 3 × 4 factor design, split for fungicide treatments, and replicated three times. With increased N and K levels, final percent leaf blighting and the standardized area under disease progress curve were higher. In fungicide-treated maize, grain yields increased with increasing levels of N and K, as expected. In non-fungicide-treated maize, grain yield increased significantly with increased levels of N, despite increased disease severity. This was in contrast to small increases in grain yields from non-fungicide-treated maize with increased K levels, which were not significant. This was probably because grain yield response, which should have occurred at higher K applications, was reduced by increased disease severity. The effect of N, P, and K on GLS wasinvestigated at Ahrens. Maize was grown in a 4 × 4 × 4 N-P-K factorial, in a randomized complete block design. Fertilizer was applied at 0, 60, 120, and 180 kg N ha-1, 0, 30, 60, and 120 kg P ha-1, and 0, 50, 100, and 150 kg K ha-1. No fungicides were applied. A single disease assessment at physiological maturity showed that final disease severity increased with increasing levels of N, P, and K. These results have implications for small-scale farmers who are encouraged to fertilize for increased grain yields but may not have the resources to apply fungicide sprays to control fungal diseases.

scholarly journals Epidemiology and management of bacterial leaf spot on watermelon caused byPseudomonas syringae

Plant Disease ◽  
2017 ◽  
Vol 101 (7) ◽  
pp. 1222-1229 ◽  
Author(s):  
E. A. Newberry ◽  
L. Ritchie ◽  
B. Babu ◽  
T. Sanchez ◽  
K. A. Beckham ◽  
...  
Keyword(s):  
Disease Severity ◽  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Negative Relationship ◽  
Disease Outbreaks ◽  
Field Trials ◽  
Multiple Regression Model ◽  
Bacterial Leaf Spot ◽  
Progress Curve ◽  
Cool Conditions

Bacterial leaf spot of watermelon caused by Pseudomonas syringae has been an emerging disease in the southeastern United States in recent years. Disease outbreaks in Florida were widespread from 2013 to 2014 and resulted in foliar blighting at the early stages of the crop and transplant losses. We conducted a series of field trials at two locations over the course of two years to examine the chemical control options that may be effective in management of this disease, and to investigate the environmental conditions conducive for bacterial leaf spot development. Weekly applications of acibenzolar-S-methyl (ASM) foliar, ASM drip, or copper hydroxide mixed with ethylene bis-dithiocarbamate were effective in reducing the standardized area under the disease progress curve (P < 0.05). Pearson’s correlation test demonstrated a negative relationship between the average weekly temperature and disease severity (–0.77, P = 0.0002). When incorporated into a multiple regression model with the square root transformed average weekly rainfall, these two variables accounted for 71% of the variability observed in the weekly disease severity (P < 0.0001). This information should be considered when choosing the planting date for watermelon seedlings as the cool conditions often encountered early in the spring season are conducive for bacterial leaf spot development.

scholarly journals Management of Daylily Rust With Different Fungicides and Fungicide Combinations

2017 ◽  
Vol 18 (3) ◽  
pp. 162-165 ◽  
Author(s):  
Robert S. Emmitt ◽  
James W. Buck
Keyword(s):  
United States ◽  
Disease Management ◽  
Disease Severity ◽  
Low Cost ◽  
Single Application ◽  
Southeast United States ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve ◽  
Disease Pressure

Production nurseries and daylily hybridizers in the southeast United States rely on the use of fungicides to manage daylily rust, caused by the fungus Puccinia hemerocallidis. Foliar sprays of pyraclostrobin, flutolanil, tebuconazole, myclobutanil, chlorothalonil, mancozeb, pyraclostrobin + boscalid, flutolanil + tebuconazole, flutolanil + myclobutanil, flutolanil + chlorothalonil, and flutolanil + mancozeb applied on 14-day intervals, and a nontreated control, were evaluated under high disease pressure at three locations in Griffin, GA, in 2015. Tebuconazole or the tebuconazole + flutolanil treatment consistently had the lowest area under the disease progress curve (AUDPC) of the treatments. The addition of flutolanil to chlorothalonil or mancozeb did not improve rust control and no difference in disease severity was observed in any treatment containing contact fungicides on all assessment dates. Single application costs ranged from $10.21 to $95.96 with tebuconazole providing excellent disease management at a relatively low cost per application ($13.90).

scholarly journals Sclerotinia Blight Resistance in Virginia-Type Peanut Transformed with a Barley Oxalate Oxidase Gene

2011 ◽  
Vol 101 (7) ◽  
pp. 786-793 ◽  
Author(s):  
D. E. Partridge-Telenko ◽  
J. Hu ◽  
D. M. Livingstone ◽  
B. B. Shew ◽  
P. M. Phipps ◽  
...  
Keyword(s):  
Oxalate Oxidase ◽  
Blight Resistance ◽  
Single Plant ◽  
Oxidase Gene ◽  
Disease Progress Curve ◽  
Sclerotinia Blight ◽  
Progress Curve ◽  
Transgenic Lines ◽  
High Level ◽  
Transgenic Peanut

Transgenic peanut lines expressing oxalate oxidase, a novel enzyme to peanut, were evaluated for resistance to Sclerotinia blight in naturally infested fields over a 5-year period. Area under the disease progress curve (AUDPC) for transgenic lines in single rows planted with seed from single-plant selections averaged 78, 83, and 90% lower than nontransgenic parents in 2004, 2005, and 2006, respectively. In addition, AUDPC in 14 transgenic lines planted with bulked seed in two-row plots averaged 81% lower compared with nontransgenic parents in 2005 and 86% lower in 16 transgenic lines in 2006. Six transgenic lines yielded 488 to 1,260 kg/ha greater than nontransgenic parents in 2005, and 10 lines yielded 537 to 2,490 kg/ha greater in 2006. Fluazinam (0.58 kg a.i./ha) fungicide sprays in 2008 and 2009 reduced AUDPC in transgenic and nontransgenic lines but AUDPC was lowest in transgenic lines. Without fluazinam, yields of transgenic lines averaged 1,133 to 1,578 kg/ha greater than nontransgenic lines in 2008 and 1,670 to 2,755 kg/ha greater in 2009. These results demonstrated that the insertion of barley oxalate oxidase in peanut conveyed a high level of resistance to Sclerotinia blight, and negated the need for costly fungicide sprays.

scholarly journals Temporal progress of southern rust in maize under different environmental conditions

2003 ◽  
Vol 28 (3) ◽  
pp. 273-278 ◽  
Author(s):  
Cláudia V. Godoy ◽  
Lílian Amorim ◽  
Armando Bergamin Filho ◽  
Herbert P. Silva ◽  
Willian J. Silva ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Disease Severity ◽  
Logistic Model ◽  
Inflection Point ◽  
Gompertz Model ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve ◽  
Puccinia Polysora ◽  
The Mean

The progress of the severity of southern rust in maize (Zea mays) caused by Puccinia polysora was quantified in staggered plantings in different geographical areas in Brazil, from October to May, over two years (1995-1996 and 1996-1997). The logistic model, fitted to the data, better described the disease progress curves than the Gompertz model. Four components of the disease progress curves (maximum disease severity; area under the disease progress curve, AUDPC; area under the disease progress curve around the inflection point, AUDPCi; and epidemic rate) were used to compare the epidemics in different areas and at different times of planting. The AUDPC, AUDPCi, and the epidemic rate were analyzed in relation to the weather (temperature, relative humidity, hours of relative humidity >90%, and rainfall) and recorded during the trials. Disease severity reached levels greater than 30% in Piracicaba and Guaíra in the plantings between December and January. Lower values of AUDPC occurred in later plantings at both locations. The epidemic rate was positively correlated (P < 0.05) with the mean daily temperatures and negatively correlated with hours of relative humidity >90%. The AUDPC was not correlated with any weather variable. The AUDPCi was negatively related to both variables connected to humidity, but not to rain. Long periods (mostly >13 h day-1) of relative humidity >90% (that corresponded to leaf wetness) occurred in Castro. Severity of southern rust in maize has always been low in Castro, thus the negative correlations between disease and the two humidity variables.

scholarly journals FIELD INOCULATION TESTS TO QUANTIFY RESISTANCE IN SPINACH TO RACES 3 AND 4 OF DOWNY MILDEW

HortScience ◽  
1992 ◽  
Vol 27 (6) ◽  
pp. 598b-598
Author(s):  
L.P. Brandenberger ◽  
J.C. Correll ◽  
T.E. Morelock ◽  
R.W. McNew
Keyword(s):  
Downy Mildew ◽  
Disease Severity ◽  
Leaf Surface ◽  
Field Inoculation ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve

Resistance to race 3 and 4 of downy mildew (Peronospora farinosa f.sp. spinaciae) was examined in separate field inoculation tests. Three Arkansas cultivars and three other commercial spinach cultivars were compared by periodically scoring individual leaves for disease severity 7 to 28 days after inoculation. Leaves were scored on a 0 to 6 scale with 0 = 0% of the leaf surface being covered with sporulation and 6 = 90-100%. Resistance was evaluated by comparing disease ratings on a given day as well as the area under the disease progress curve. Arkansas spinach cultivars exhibited significantly lower disease severity ratings in field inoculation tests for all sample dates for both races 3 and 4 when compared to known susceptible cultivars.

scholarly journals Potential of Fungal Endophytes to Antagonise Puccinia striiformis Causing Wheat Yellow Rust

2019 ◽  
Author(s):  
Hafiz Arslan Anwaar ◽  
Rashida Perveen ◽  
Muhammad Zeeshan Mansha ◽  
Hafiz Muhammad Aatif ◽  
Zahid Mahmood Sarwar ◽  
...  
Keyword(s):  
Grain Yield ◽  
Disease Severity ◽  
Yellow Rust ◽  
Fungal Endophytes ◽  
Colletotrichum Lindemuthianum ◽  
Wheat Genotypes ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve ◽  
Yield Gain

In this study, we evaluated the potential of fungal endophytes to control yellow rust in wheat (Triticum aestivum L.) as endophytes are beneficial microbes and alternate to pesticides for confronting pathogens. The in-vitro efficacy of the fungal endophytes isolated from different desert plants was evaluated and the best four namely Colletotrichum lindemuthianum, Piriformospora indica, Acremonium lolii and Trichoderma viride were selected. Seeds of two susceptible wheat genotypes namely Fareed-06 and Shafaq-06 obtained from screening experiment were inoculated by dipping in four endophytic spore suspensions and were sown using randomized complete block design under factorial arrangement. Data concerning about area under disease progress curve, final disease severity percentage, coefficient of infection,1000- grains weight and grain yield were recorded. Results showed that endophyte P. indica showed significant decrease in final disease severity (FDS) and area under disease progress curve (AUDPC), resultantly 12.2% grain yield gain in rust susceptible wheat genotypes of Fareed-06 and Shafaq-06 followed by the endophytes T. viride, C. lindemuthianum and A. lolii with the grain yield gain of 10.6%, 06.2% and 04.2% respectively. In crux, fungal endophytes are valuable microbes which can be employed to induce tolerance against P. striiformis in yellow rust vulnerable areas for better and sustainable wheat production.

scholarly journals Reaction of beet genotypes to the Beet Leaf Spot in the upper Valley of Itajaí, Santa Catarina state, Brazil

2015 ◽  
Vol 33 (1) ◽  
pp. 106-109
Author(s):  
Leandro L Marcuzzo ◽  
Tatiana S Duarte ◽  
Patrícia C Hilleshein ◽  
Bruno T Scheidt
Keyword(s):  
Disease Severity ◽  
Leaf Spot ◽  
Rating Scale ◽  
Santa Catarina ◽  
Yield Data ◽  
Local Conditions ◽  
Family Farmers ◽  
Progress Curve ◽  
Sowing Dates ◽  
Santa Catarina State

In the region of the Upper Valley of Itajaí, Santa Catarina state, Brazil, family farmers cultivate beet (Beta vulgaris) along with other products such as, onion. However, some diseases, including the Beet Leaf Spot (Cercospora beticola), have compromised the success of the beet crop due to severe leaf incidence. The objective of this study was to evaluate the reaction to the Beet Leaf Spot, under local conditions, in the spring-summer season, of the beet cultivars most frequently used by farmers in the region, namely All Green, Stays Green, Early Wonder, Cabernet, Boro, Modana and Itapuã. Two experiments, with a 30-day interval between sowings were carried out in EPAGRI, Experimental Station of Ituporanga. The experimental design was of randomized complete blocks with four replications and 2,25 m² plots. Disease severity was assessed weekly, using a diagrammatic rating scale, in ten plants taken at random and previously labelled. Disease severity data were used to calculate the area under the disease progress curve (AUDPC) for each cultivar. Same plants were used to estimate yield. AUDPC and yield data were submitted to analysis of variance (F-test, 5% probability), and means were studied by the Scott-Knott test (5% probability). There were no significant differences between cultivars, nor for reaction to the disease, neither for yield, in any of the two sowing dates. In both experiments, cultivar All Green scored the highest severity value in the last assessments, 18.46 and 19.84% respectively in the first and second sowing dates, while hybrid Boro (17.79%) in the first experiment, and Stays Green and Cabernet (18.04%) in the second, recorded the lowest values. We concluded that all cultivars were susceptible to the Beet Leaf Spot in spring-summer conditions in the Upper Valley of Itajaí.

scholarly journals Ramularia leaf spot severity and effects on cotton leaf area and yield1

2016 ◽  
Vol 46 (4) ◽  
pp. 434-441
Author(s):  
João Paulo Ascari ◽  
◽  
Inês Roeder Nogueira Mendes ◽  
Vanessa Costa da Silva ◽  
Dejânia Vieira de Araújo
Keyword(s):  
Leaf Area ◽  
Leaf Spot ◽  
Yield Loss ◽  
Cotton Leaf ◽  
Cotton Yield ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve ◽  
Ramularia Leaf Spot ◽  
Upper Third

ABSTRACT Cotton monoculture favors the development of diseases such as ramularia leaf spot, which causes early defoliation and boll rotting, thus decreasing yield. This study aimed at evaluating the severity of ramularia leaf spot and its effects on cotton leaf area and yield. The experiment was conducted in a triple (4 x 3 x 2) factorial design, consisting of four cultivars (FM940GLT, FM944GL, TMG42WS and TMG43WS), three thirds of the plant (lower, middle and upper) and two management conditions (with and without fungicide application). To the variable area under the disease progress curve, the lowest values were observed in the upper third of the TMG42WS and TMG43WS cultivars, with the lower and middle thirds presenting the highest severity. The condition managed with fungicide and the upper third showed the lowest values for area under the disease progress curve. The leaf area was negatively affected by the ramularia leaf spot. Concerning the seed and fiber yields, the highest averages were observed for the middle third and the condition managed with fungicide. There was no statistical difference for cotton yield loss.

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