scholarly journals Influence of Temperature and Relative Humidity on Sporulation of Cercospora zeae-maydis and Expansion of Gray Leaf Spot Lesions on Maize Leaves

Plant Disease ◽  
2005 ◽  
Vol 89 (6) ◽  
pp. 624-630 ◽  
Author(s):  
P. A. Paul ◽  
G. P. Munkvold
Keyword(s):  
Relative Humidity ◽  
Leaf Spot ◽  
Quadratic Function ◽  
Leaf Tissue ◽  
Gray Leaf Spot ◽  
Quadratic Model ◽  
Effect Of Temperature ◽  
Cercospora Zeae Maydis ◽  
Maize Leaves ◽  
Effects Of Temperature

Controlled environment studies were conducted to determine the effects of temperature on the expansion of lesions of gray leaf spot, and the effects of temperature and relative humidity on the sporulation of Cercospora zeae-maydis on maize (Zea mays). For the lesion expansion experiment, potted maize plants were spray inoculated at growth stage V6, bagged, and incubated at 25 to 28°C and 100% relative humidity for 36 to 40 h. Symptomatic plants were transferred to growth chambers and exposed to constant temperatures of 25, 30, and 35°C. Lesion area (length by width) was measured at 4-day intervals for 17 days. For sporulation studies, lesions were excised from naturally infected maize leaves, measured, and incubated at constant temperature (20, 25, 30, or 35°C) and relative humidity (70, 80, 90, or 100%) for 72 h. Sporulation was estimated as the number of conidia per square centimeter of diseased leaf tissue. A quadratic function was used to model the relationship between log-transformed conidia per square centimeter at 100% relative humidity and temperature. Temperature had a significant effect on lesion expansion (P ≤ 0.05). At 25 and 30°C, the rate of lesion expansion was significantly higher than at 35°C (P ≤ 0.05). The largest lesions and the highest mean rate of lesion expansion were observed at 30°C; however, the mean lesion expansion rate at this temperature was not significantly different from that at 25°C. The interaction effect of temperature and relative humidity on the log of conidia per square centimeter of diseased tissue was significant (P ≤ 0.05). At 100% relative humidity, the effect of temperature on sporulation was significant (P ≤ 0.05), with maximum spore production occurring at 25 and 30°C. The quadratic model explained between 49 and 80% of the variation in the log of conidia per square centimeter at 100% with variation in temperature. These results suggest that the rapid increase in gray leaf spot severity generally observed during mid- and late summer may be due to favorable conditions for lesion expansion during this period. When relative humidity is >95%, expanding lesions may serve as a source of inoculum for secondary infections.

scholarly journals The Effect of Temperature and Humidity May Reduce the Growth Rate of the Coronavirus Disease 2019 Epidemic

2020 ◽  
Author(s):  
Lei Qin ◽  
Qiang Sun ◽  
Jiani Shao ◽  
Yang Chen ◽  
Xiaomei Zhang ◽  
...  
Keyword(s):  
Growth Rate ◽  
Relative Humidity ◽  
Effect Of Temperature ◽  
Average Temperature ◽  
Temperature And Humidity ◽  
Scatter Plots ◽  
Low Humidity ◽  
Average Relative Humidity ◽  
Effects Of Temperature ◽  
The Relationship

Abstract Background: The effects of temperature and humidity on the epidemic growth of coronavirus disease 2019 (COVID-19)remains unclear.Methods: Daily scatter plots between the epidemic growth rate (GR) and average temperature (AT) or average relative humidity (ARH) were presented with curve fitting through the “loess” method. The heterogeneity across days and provinces were calculated to assess the necessity of using a longitudinal model. Fixed effect models with polynomial terms were developed to quantify the relationship between variations in the GR and AT or ARH.Results: An increased AT dramatically reduced the GR when the AT was lower than −5°C, the GR was moderately reduced when the AT ranged from −5°C to 15°C, and the GR increased when the AT exceeded 15°C. An increasedARH increased theGR when the ARH was lower than 72% and reduced theGR when the ARH exceeded 72%.Conclusions: High temperatures and low humidity may reduce the GR of the COVID-19 epidemic. The temperature and humidity curves were not linearly associated with the COVID-19 GR.

scholarly journals Effects of Temperature, Relative Humidity, and Plant Age on Bacterial Disease of Onion Plants

2019 ◽  
Vol 20 (4) ◽  
pp. 200-206
Author(s):  
Kim E. Tho ◽  
Elizabeth Brisco-McCann ◽  
Prissana Wiriyajitsomboon ◽  
Mary K. Hausbeck
Keyword(s):  
Relative Humidity ◽  
Management Strategies ◽  
Bacterial Pathogen ◽  
Plant Age ◽  
Effect Of Temperature ◽  
Bacterial Disease ◽  
Disease Symptoms ◽  
Foliar Disease ◽  
Progress Curve ◽  
Effects Of Temperature

Foliar disease of onion in Michigan, caused by Pantoea agglomerans, Pantoea ananatis, or Enterobacter cowanii, has recently become a concern to producers. The objective of this study was to determine the effect of temperature, relative humidity (RH), and plant age in growth chamber and greenhouse experiments on onion plants inoculated with each pathogen. A significant level of disease resulted from each pathogen at 25 to 30°C, with strong positive associations detected using regression analysis between the area under the disease progress curve (AUDPC) and temperature. RH also significantly influenced symptom development. Foliar disease symptoms developed sooner and were more severe when RH was high (80 to 100%) but was limited at RH < 60%. Significant positive associations between RH and AUDPC, as described by linear regression, were also detected. When 6- to 14-week-old plants were inoculated with each bacterial pathogen, susceptibility increased significantly with age. These results provide insight into the epidemiology of P. agglomerans, P. ananatis, and E. cowanii bacterial pathogens of onions in Michigan and can assist in the development and timing of management strategies.

scholarly journals Effects of Climate on Incidence of Campylobacter spp. in Humans and Prevalence in Broiler Flocks in Denmark

2004 ◽  
Vol 70 (12) ◽  
pp. 7474-7480 ◽  
Author(s):  
Mary Evans Patrick ◽  
Lasse Engbo Christiansen ◽  
Michael Wainø ◽  
Steen Ethelberg ◽  
Henrik Madsen ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Linear Models ◽  
Public Health Problem ◽  
Effect Of Temperature ◽  
Maximum Temperature ◽  
Future Research ◽  
Combined Effects ◽  
Average Temperature ◽  
Effects Of Temperature ◽  
Single Predictor

ABSTRACT Campylobacter infections are increasing and pose a serious public health problem in Denmark. Infections in humans and broiler flocks show similar seasonality, suggesting that climate may play a role in infection. We examined the effects of temperature, precipitation, relative humidity, and hours of sunlight on Campylobacter incidence in humans and broiler flocks by using lag dependence functions, locally fitted linear models, and cross validation methods. For humans, the best model included average temperature and sunlight 4 weeks prior to infection; the maximum temperature lagged at 4 weeks was the best single predictor. For broilers, the average and maximum temperatures 3 weeks prior to slaughter gave the best estimate; the average temperature lagged at 3 weeks was the best single predictor. The combined effects of temperature and sunlight or the combined effects of temperature and relative humidity predicted the incidence in humans equally well. For broiler flock incidence these factors explained considerably less. Future research should focus on elements within the broiler environment that may be affected by climate, as well as the interaction of microclimatic factors on and around broiler farms. There is a need to quantify the contribution of broilers as a source of campylobacteriosis in humans and to further examine the effect of temperature on human incidence after this contribution is accounted for. Investigations should be conducted into food consumption and preparation practices and poultry sales that may vary by season.

scholarly journals Genetic Relatedness of African and United States Populations of Cercospora zeae-maydis

2000 ◽  
Vol 90 (5) ◽  
pp. 486-490 ◽  
Author(s):  
Larry D. Dunkle ◽  
Morris Levy
Keyword(s):  
United States ◽  
Sibling Species ◽  
Leaf Spot ◽  
The United States ◽  
Gray Leaf Spot ◽  
Ancestral Population ◽  
Aflp Analysis ◽  
Group I ◽  
Cercospora Zeae Maydis ◽  
Group Ii

Two taxonomically identical but genetically distinct sibling species, designated groups I and II, of Cercospora zeae-maydis cause gray leaf spot of maize in the United States. Isolates of the gray leaf spot pathogen from Africa were compared with isolates from the United States by amplified fragment length polymorphism (AFLP) analysis and restriction digests of internal transcribed spacer (ITS) regions and 5.8S ribosomal DNA (rDNA), as well as by morphological and cultural characteristics. The isolates from Africa were morphologically indistinguishable from the U.S. isolates in both groups, but like isolates of group II, they grew more slowly and failed to produce detectable amounts of cercosporin in culture. Analysis of restriction fragments from the ITS and rDNA regions digested with five endonucleases indicated that all of the African isolates shared the profile of the C. zeae-maydis group II population from the eastern United States and, thus, are distinct from the group I population, which is more prevalent in the United States and other parts of the world. Cluster analysis of 85 AFLP loci confirmed that the African and U.S. group II populations were conspecific (greater than 97% average similarity) with limited variability. Among all group II isolates, only 8 of 57 AFLP loci were polymorphic, and none was specific to either population. Thus, although gray leaf spot was reported in the United States several decades prior to the first record in Africa, the relative age of the two populations on their respective continents could not be ascertained with confidence. The absence of C. zeae-maydis group I in our samples from four countries in the major maize-producing region of Africa as well as the greater AFLP haplotype diversity found in the African group II population, however, suggest that Africa was the source of C. zeae-maydis group II in the United States. The overall paucity of AFLP variation in this sibling species further suggests that its origin is recent or that the ancestral population experienced a severe bottleneck prior to secondary migration.

scholarly journals Effects of Temperature and Moisture on Sporulation and Infection by Pseudoperonospora cubensis

Plant Disease ◽  
2017 ◽  
Vol 101 (4) ◽  
pp. 562-567 ◽  
Author(s):  
Shiling Sun ◽  
Sen Lian ◽  
Shulian Feng ◽  
Xiangli Dong ◽  
Caixian Wang ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Downy Mildew ◽  
Weibull Model ◽  
Infection Process ◽  
Effect Of Temperature ◽  
Effective Control ◽  
Pseudoperonospora Cubensis ◽  
Cucumber Downy Mildew ◽  
Effects Of Temperature ◽  
Modified Weibull

Cucumber downy mildew, caused by Pseudoperonospora cubensis, is a worldwide disease that causes severe damage to cucumber production. The effects of temperature and moisture on sporulation and infection by P. cubensis were investigated by inoculating cucumber (‘85F12’) cotyledons with sporangia and examining the sporangia produced on the inoculated cotyledons under artificially controlled environments. The result showed that the temperature required for sporangium infection by P. cubensis and sporulation of the downy mildew lesions occurred at 5 to 30°C. The optimal temperature estimated by the fitted model was 18.8°C for sporangium infection and 16.2°C for downy mildew lesion sporulation. The pathogen formed plenty of sporangia when disease cotyledons were wetted or in the environment with relative humidity = 100%. The downy mildew lesions produced only a few sporangia when placed in the environment with relative humidity = 90%. The inoculated cotyledons, which incubated for 5 days at about 20°C in a dry greenhouse, began to form sporangia 4 h after being wetted when incubated in darkness. The quantity of sporangia produced on the downy mildew lesions increased with extension of incubating period (within 12 h), and the relationship between produced sporangia and the incubation period at 15, 20, and 25°C can be described by three exponential models. The observed minimum wetness durations (MWD) required for sporangia to complete the infection process and cause downy mildew were 12, 4, 2.5, 1, 1, and 6 h for 5, 10, 15, 20, 25, and 30°C, respectively. The effect of temperature and wetness duration on infection by sporangia of P. cubensis can be described by the modified Weibull model. The shortest MWD was 0.45 h, about 27 min, estimated by model. The experimental data and models will be helpful in the development of forecasting models and effective control systems for cucumber downy mildew.

Assessing Late Vegetative and Tasseling Fungicide Application Timings on Foliar Disease and Yield in Indiana Corn

2020 ◽  
Vol 21 (4) ◽  
pp. 224-229
Author(s):  
Darcy E. P. Telenko ◽  
Jeffrey D. Ravellette ◽  
Kiersten A. Wise
Keyword(s):  
Leaf Spot ◽  
The United States ◽  
Field Trials ◽  
Gray Leaf Spot ◽  
Corn Production ◽  
Foliar Disease ◽  
Application Timing ◽  
Cercospora Zeae Maydis ◽  
Foliar Fungicide ◽  
Disease Pressure

Gray leaf spot (Cercospora zeae-maydis) is a foliar disease of corn (Zea mays) that consistently reduces yields across the United States and is an annual concern in Indiana corn production. Field trials were conducted in West Lafayette, IN, over 3 years (2016 to 2018) to evaluate the effectiveness of 12-leaf collar stage (V12) foliar fungicide applications compared with tasseling (VT) applications for gray leaf spot management and yield. Results indicated that during years in which foliar disease severity was less than 4%, there was no effect of application timing on gray leaf spot severity. In 2018, when gray leaf spot levels exceeded 5%, significantly less disease was observed in treatments receiving VT applications compared with V12 applications. Application timing did not affect yield in any year of the experiment. In 2016, benzovindiflupyr + azoxystrobin + propiconazole resulted in greater yields compared with the nontreated control, and in 2018, pyraclostrobin + metconazole and benzovindiflupyr + azoxystrobin + propiconazole resulted in greater yields compared with the nontreated control. This research indicates that in high disease pressure environments and years, Indiana farmers may want to continue to apply fungicides at VT rather than apply prior to tassel.

scholarly journals Baseline Sensitivity of Cercospora zeae-maydis to Quinone Outside Inhibitor Fungicides

Plant Disease ◽  
2011 ◽  
Vol 95 (2) ◽  
pp. 189-194 ◽  
Author(s):  
C. A. Bradley ◽  
D. K. Pedersen
Keyword(s):  
United States ◽  
Leaf Spot ◽  
The United States ◽  
Gray Leaf Spot ◽  
Alternative Respiration ◽  
Baseline Sensitivity ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Cercospora Zeae Maydis

Cercospora zeae-maydis, the causal agent of gray leaf spot on corn (Zea mays), can cause severe yield loss in the United States. Quinone outside inhibitor (QoI) fungicides are effective tools that can be used to manage gray leaf spot, and their use has increased in corn production in the United States. In total, 61 C. zeae-maydis isolates collected from fields in which QoI fungicides had never been applied were tested in vitro using azoxystrobin-, pyraclostrobin-, or trifloxystrobin-amended medium to determine the effective fungicide concentration at which 50% of the conidial germination was inhibited (EC50). The effect of salicylhydroxamic acid (SHAM) also was evaluated for seven isolates to determine whether C. zeae-maydis is capable of using alternative respiration in azoxystrobin-amended medium. All seven C. zeae-maydis isolates tested had significantly greater (P < 0.02) EC50 values when SHAM was not included in medium amended with azoxystrobin, indicating that C. zeae-maydis has the potential to utilize alternative respiration to overcome QoI fungicide inhibition in vitro. Baseline EC50 values of azoxystrobin ranged from 0.003 to 0.031 μg/ml, with mean and median values of 0.018 and 0.019 μg/ml, respectively. Baseline EC50 values of pyraclostrobin ranged from 0.0003 to 0.0025 μg/ml, with mean and median values of 0.0010 and 0.0010 μg/ml, respectively. Baseline EC50 values of trifloxystrobin ranged from 0.0004 to 0.0034 μg/ml, with mean and median values of 0.0023 and 0.0024 μg/ml, respectively. These baseline sensitivity values will be used in a fungicide resistance monitoring program to determine whether shifts in sensitivity to QoI fungicides are occurring in C. zeae-maydis populations.

scholarly journals Relationships of Environmental and Cultural Factors with Severity of Gray Leaf Spot in Maize

Plant Disease ◽  
2002 ◽  
Vol 86 (10) ◽  
pp. 1127-1133 ◽  
Author(s):  
Alka Bhatia ◽  
G. P. Munkvold
Keyword(s):  
Relative Humidity ◽  
Disease Severity ◽  
Leaf Spot ◽  
Cultural Influences ◽  
The United States ◽  
Gray Leaf Spot ◽  
Planting Date ◽  
Time Duration ◽  
Best Fitting ◽  
Fitting Model

Gray leaf spot of maize caused by Cercospora zeae-maydis is a major foliar disease in the United States and other parts of the world. Efficient management of gray leaf spot is hindered by a lack of quantitative information regarding environmental and cultural influences on disease severity. We collected environmental, cultural, and disease severity data in southern Iowa at 13 locations in 1998 and 11 locations in 1999. The independent variables that we considered included temperature, relative humidity, leaf wetness, percent maize residue cover, distance to nearest maize residue, planting date, and previous crop. A time-duration value (TDV) variable was created to represent cumulative hours of favorable temperature (22 ≤ T ≤ 30°C) and relative humidity (≥95%). Disease severity was assessed at 2-week intervals on three to eight maize genotypes differing in gray leaf spot resistance and maturity at each location. Environmental, cultural, and disease data were summarized for four different periods during the growing season and analyzed by stepwise multiple linear regression in order to determine which variables significantly contributed to gray leaf spot severity at the dough or dent growth stages of maize. In 1998, genotype resistance, planting date, distance to nearest maize residue, wetness duration, and TDV had significant effects on disease severity. R2 values were similar among the four periods. The best-fitting model for the 1998 data had an R2 of 0.65. With 1998 and 1999 data combined, results were similar except that percent maize residue cover was significant rather than distance to nearest maize residue. The best-fitting model had an R2 of 0.55. The 2-year model utilizing only the weather variables from emergence to 2 weeks before silking had an R2 value of 0.43. Strong linear relationships existed between gray leaf spot severity and genotype resistance, maize surface residue, planting date, and TDV. These results can serve as a foundation for the development of a prediction model for gray leaf spot severity on maize.

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