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 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 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 Fungicides for Control of Downy Mildew on Pickling Cucumber in Michigan

2019 ◽  
Vol 20 (3) ◽  
pp. 165-169 ◽  
Author(s):  
Katelyn E. Goldenhar ◽  
Mary K. Hausbeck
Keyword(s):  
Downy Mildew ◽  
Untreated Control ◽  
Field Studies ◽  
Pseudoperonospora Cubensis ◽  
Relative Area ◽  
Disease Progress Curve ◽  
Cucurbit Downy Mildew ◽  
Disease Progress ◽  
Pickling Cucumber ◽  
Progress Curve

Michigan growers rely on fungicides to limit cucurbit downy mildew (CDM), incited by Pseudoperonospora cubensis; resistance of the pathogen to fungicides is a concern. We evaluated fungicides against CDM in Michigan field studies from 2015 to 2017. According to the relative area under the disease progress curve (rAUDPC), in 2015, mandipropamid, propamocarb, fluxapyroxad/pyraclostrobin, copper octanoate, and dimethomorph resulted in disease levels similar to the control. These treatments, along with cymoxanil, were similar to the control in 2016. Fungicides that were ineffective during 2015 and 2016 did not limit CDM in 2017. Famoxadone/cymoxanil and fluopicolide did not limit CDM in 2017. Each year, the following treatments were similar for disease based on rAUDPC data: oxathiapiprolin applied alone or premixed with chlorothalonil or mandipropamid, ametoctradin/dimethomorph, fluazinam, mancozeb/zoxamide, cyazofamid, and ethaboxam. An exception occurred in 2017, when ethaboxam was less effective than fluazinam, oxathiapiprolin/chlorothalonil, and oxathiapiprolin/mandipropamid. Mancozeb and chlorothalonil treatments were similar in 2015 and 2017, according to rAUDPC data. In 2017, yields were increased for oxathiapiprolin/chlorothalonil, oxathiapiprolin/mandipropamid, mancozeb, ametoctradin/dimethomorph, mancozeb/zoxamide, ethaboxam, cyazofamid, chlorothalonil, and fluazinam compared with the untreated control.

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.

Use Of a Simulation Model to Explore Fungicide Strategies for Control of Cercospora Leafspot of Peanut1

1988 ◽  
Vol 15 (1) ◽  
pp. 39-43 ◽  
Author(s):  
G. R. Knudsen ◽  
C. S. Johnson ◽  
H. W. Spurr
Keyword(s):  
Simulation Model ◽  
Disease Severity ◽  
Weather Conditions ◽  
Field Trials ◽  
Computer Simulation Model ◽  
Financial Benefit ◽  
Advisory Program ◽  
Disease Progress Curve ◽  
Disease Progress ◽  
Progress Curve

Abstract A sub-model describing persistence and efficacy of chlorothalonil fungicide was incorporated into a computer simulation model of Cercospora leafspot of peanut. The resultant model was validated using independent data sets from field trials over a two-year period. Predicted disease progress curves and area under the disease progress curve for different fungicide application schedules and rates were compared with field observations. The model was then used to compare predicted disease severity and area under the disease progress curve (AUDPC) for a calendar spray schedule vs a leafspot advisory program under different weather conditions. Predicted disease severity levels and area under disease progress curves were similar for advisory and calendar spray schedules. Results were insensitive to changes in parameters describing fungicide persistence or efficacy. The model described herein is a good estimator of the combined effects of weather and chlorothalonil treatments on disease progress, effectively ranks treatments or environmental conditions in terms of their effect on leafspot, and provides a basis for comparison of fungicide scheduling strategies. The simulation model predicted AUDPC more accurately than end-of-season disease, and AUDPC is a more reliable indicator of the effect of peanut leafspot disease on yield loss. Simulation experiments will be useful in optimizing fungicide or biocontrol strategies for long-term financial benefit to growers.

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 Alternative Products to Control Soybean Downy Mildew in the Field

2020 ◽  
Vol 12 (8) ◽  
pp. 160
Author(s):  
Gislaine Gabardo ◽  
Maristella Dalla Pria ◽  
Henrique Luis da Silva ◽  
Mônica Gabrielle Harms
Keyword(s):  
Downy Mildew ◽  
Disease Severity ◽  
Field Experiments ◽  
Ascophyllum Nodosum ◽  
Phenological Stages ◽  
Manganese Zinc ◽  
Growing Seasons ◽  
Progress Curve ◽  
Copper Manganese ◽  
Diagrammatic Scale

Soybean mildew caused by Oomycota Peronospora manshurica, is a disease widely spread in Brazil. In order to study the efficiency of soybean mildew control due to the application of alternative products and fungicide in the field, experiments were conducted in Ponta Grossa, PR, Brazil, during the 2013/2014 and 2014/2015 growing seasons. The design used was randomized blocks with four replications. The treatments were: 1-witness; 2-acibenzolar-S-methyl; 3-calcium; 4-micronutrients: copper, manganese and zinc; 5-micronutrients: manganese, zinc and molybdenum; 6-NK fertilizer; 7-Ascophyllum nodosum and 8-azoxystrobin + cyproconazole with the addition of Nimbus adjuvant. Four applications of alternative products (phenological stages V3, V6, R1 and R5.1) and two of fungicide (phenological stages R1 and R5.1) were performed. The mildew severity was estimated using a diagrammatic scale. The severity data made it possible to calculate the area under the disease progress curve (AUDPC). In the 2014/2015 harvest the disease was more severe. The control of downy mildew by the use of fungicide did not reduce the epidemic. The fungicide was not efficient in the two evaluated seasons. All tested alternative products reduced the disease severity and AUDPC in both seasons. The best results in reducing downy mildew were found with the application of acibenzolar-S-methyl, micronutrients (Cu, Mn, Zn) and A. nodosum.

Comparative Performance of Sanitizers in Managing Plant-to-plant Transfer and Postharvest Infection of Calonectria pseudonaviculata and Pseudonectria foliicola on Boxwood

Plant Disease ◽  
2021 ◽  
Author(s):  
Ravi Bika ◽  
Warren Copes ◽  
Fulya Baysal-Gurel
Keyword(s):  
Shelf Life ◽  
Disease Severity ◽  
Ammonium Compound ◽  
Conidial Suspension ◽  
Rooted Cuttings ◽  
Disease Progress ◽  
Progress Curve ◽  
Significant Difference ◽  
Plant Transfer ◽  
Blight Disease

Calonectria pseudonaviculata and Pseudonectria foliicola causing the infamous ‘boxwood blight’ and ‘Volutella blight’, respectively, are a constant threat to the boxwood production and cut boxwood greenery market. Both pathogens cause significant economic loss to all parties (growers, retailer, and customers) in the horticultural chain. The objective of this study was to evaluate efficacy of disinfesting chemicals [quaternary ammonium compound (QAC), peroxy, acid, alcohol, chlorine, cleaner] in preventing plant-to-plant transfer of C. pseudonaviculata and P. foliicola via cutting tools, as well as reduction of postharvest boxwood blight and Volutella blight disease severity in harvested boxwood greenery. First, an in vitro study was conducted to select products and doses that completely or near-completely inhibited conidial germination of C. pseudonaviculata and P. foliicola. The selected treatments were also tested for their ability to reduce plant-to-plant transfer of C. pseudonaviculata and P. foliicola and manage postharvest boxwood blight and Volutella blight in boxwood cuttings. For the plant-to-plant transfer study, Felco 19 shears were used as a tool for mechanical transfer of fungal conidia. The blades of Felco 19 shears were exposed to a conidial suspension of C. pseudonaviculata or P. foliicola by cutting a 1 cm diameter cotton roll that had been dipped into a fungal suspension. Disease-free boxwood rooted cuttings (10 cm height) were pruned with the contaminated shears. The Felco 19 shears were equipped with a mounted miniature sprayer connected to a pressurized reservoir of treatment solution that automatically sprayed the blade and plant surface while cutting. The influence of accumulated sap on the shear blade was studied through 1- or 10-cut pruning variable on test plants and screened for the efficacy of treatments. Then, the boxwood rooted cuttings were transplanted and incubated in room conditions (21 °C, 60% RH) with 12 h of fluorescent light; data evaluation on disease severity was done weekly for a month. Disease progress [area under disease progress curve (AUDPC)] was calculated. In another study, postharvest dip application treatments were used for the management of postharvest boxwood blight or Volutella blight on boxwood cuttings. The harvested boxwood cuttings were inoculated with a conidial suspension of C. pseudonaviculata or P. foliicola, then dipped into treatment solution 3 days afterwards. The treated boxwood cuttings were kept in room conditions, and boxwood blight or Volutella blight disease severity as well as marketability (postharvest shelf life) assessed every 2 days for 1 week. A significant difference between treatments was observed for reduction of boxwood blight or Volutella blight severity and AUDPC. The treatments (ODD + DoD + DdD + DB)AC [Simple Green D Pro 5], 2 propanol + DDAC (0.12%) [KleenGrow], and DBAC + DEAC [GreenShield] were the most effective in reducing the plant to plant transfer of boxwood blight and Volutella blight when pruned with contaminated Felco 19 shears. In addition to the three effective treatments above, acetic acid (2.5%) [Vinegar], 2-propanol + DDAC (0.06%), sodium hypochlorite (Clorox) and potassium peroxymonosulfate + NaCl (2%) [Virkon] were effective in reducing postharvest boxwood blight whereas DBAC + DBAC [Lysol all-purpose cleaner], ethanol [70% (Ethyl alcohol)] and DDAC +DBAC [Simple Green D Pro 3 plus] were effective in reducing Volutella blight disease severity and AUDPC, and also maintained better quality and longer postharvest shelf life of boxwood cuttings when applied as a dip treatment. The longer postharvest shelf life of boxwood cuttings noted may be attributed to reduced disease severity and AUDPC resulting in healthy boxwood cuttings.

Temporal Dynamics and Severity of Cucurbit Downy Mildew Epidemics as Affected by Chemical Control and Cucurbit Host Type

Plant Disease ◽  
2021 ◽  
Author(s):  
Isaack Kikway ◽  
Anthony P. Keinath ◽  
Peter S. Ojiambo
Keyword(s):  
Downy Mildew ◽  
Disease Severity ◽  
Temporal Dynamics ◽  
Parameter Estimates ◽  
Spring Season ◽  
Fall Season ◽  
Fungicide Treatment ◽  
Cucurbit Downy Mildew ◽  
Disease Progress ◽  
Host Type

Cucurbit downy mildew caused by the oomycete Pseudoperonospora cubensis is an important disease that affects members of Cucurbitaceae family globally. However, temporal dynamics of the disease have not been characterized at the field scale to understand how control strategies influence disease epidemics. Disease severity was assessed visually on cucumber and summer squash treated with weekly alternation of chlorothalonil with either cymoxanil, fluopicolide or propamocarb, during the 2018 spring season and 2019 and 2020 fall seasons in North Carolina, and the 2018 and 2020 fall seasons in South Carolina. Disease onset was observed around mid-June during the spring season and early September during the fall season, followed by a rapid increase in severity until mid-July in the spring season and late September or mid-October in the fall season, typical of polycyclic epidemics. The Gompertz, logistic and monomolecular growth models were fitted to disease severity using linear regression and parameter estimates used to compare the effects of fungicide treatment and cucurbit host type on disease progress. The Gompertz and logistic models were more appropriate than the monomolecular model in describing temporal dynamics of cucurbit downy mildew, with the Gompertz model providing the best description for 34 of the 44 epidemics examined. Fungicide treatment and host type significantly (P < 0.0001) affected standardized area under disease progress curve (sAUDPC), final disease severity (Final DS) and weighted mean absolute rates of disease progress (ρ), with these variables, in most cases, being significantly (P < 0.05) lower in fungicide treated plots than in untreated control plots. Except in a few cases, sAUDPC, Final DS and ρ were lower in cases where chlorothalonil was alternated with fluopicolide or propamocarb than in cases where chlorothalonil alternated with cymoxanil or when chlorothalonil was applied alone. These results characterized the temporal progress of cucurbit downy mildew and provided an improved understanding of the dynamics of the disease at the field level. Parameters of disease progress obtained from this study could serve as inputs in simulation studies to assess the efficacy of fungicide alternation in managing fungicide resistance in this pathosystem.

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