Influence of Tillage on Development of Gray Leaf Spot and Number of Airborne Conidia of Cercospora zeae-maydis

Plant Disease ◽  
1987 ◽  
Vol 71 (4) ◽  
pp. 329 ◽  
Author(s):  
G. A. Payne
Keyword(s):  
Leaf Spot ◽  
Gray Leaf Spot ◽  
Cercospora Zeae Maydis ◽  
Airborne Conidia

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.

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 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 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 First Report of Gray Leaf Spot Caused by Cercospora zeae-maydis on Corn in Ontario, Canada

Plant Disease ◽  
2002 ◽  
Vol 86 (3) ◽  
pp. 327-327 ◽  
Author(s):  
X. Zhu ◽  
L. M. Reid ◽  
T. Woldemariam ◽  
A. Tenuta ◽  
A. W. Schaafsma
Keyword(s):  
Leaf Spot ◽  
Room Temperature ◽  
Gray Leaf Spot ◽  
State University ◽  
Iowa State University ◽  
Single Spore ◽  
Corn Hybrids ◽  
Agar Culture ◽  
Basic Plant ◽  
Cercospora Zeae Maydis

During an annual corn disease survey in mid-September 2001, sporadic symptoms typical of gray leaf spot (causal agent Cercospora zeae-maydis Tehon & E.Y. Daniels) (4), consisting of long, narrow, rectangular, 0.3 to 0.5 × 2 to 5 cm, tan or gray-to-tan spots, were found in nine fields in southern Ontario. Leaf samples with symptoms were placed in petri dishes containing moistened filter paper to maintain high humidity and stored at room temperature for 48 h. Clustered conidiophores arose from stomata on both leaf surfaces. Slightly curved, hyaline conidia, 4 to 8 × 25 to 88 µm long with 3 to 5 septa appeared on the tops of conidiophores, similar to those described by Kingsland (3). When single-spore isolates were cultured on carrot leaf decoction agar (2) at room temperature, aerial mycelia were rare, but slightly larger conidia were produced in 3 weeks. When single-spore isolates were cultured on V8 agar (1) at room temperature, aerial mycelia were abundant, and conidiophores and conidia were produced on the tops of mycelia in 1 to 2 weeks, but conidia were slightly smaller. Greenhouse-grown plants of two commercial corn hybrids (Pioneer 32Y52 and Zimmerman NX7208) were inoculated at the 8- to 10-leaf stage by injecting a suspension of 5 × 103 conidia per ml (washed from a V8 agar culture with sterile water) into the whorl and by spraying the suspension on the leaves. High moisture was maintained in the greenhouse by a misting system. After 14 to 21 days, typical symptoms of gray leaf spot and typical conidiophores and conidia were observed. Gray leaf was reisolated from inoculated plants, fulfilling Koch's postulates. We have suspected that gray leaf spot has been present in Ontario for a few years based on unconfirmed reports from the seed corn industry, but to our knowledge, this is the first confirmed report of this pathogen in Canada. Voucher specimens of field material, dried cultures, and greenhouse-inoculated leaves have been deposited in the National Mycological Herbarium (DAOM 229597 to 229600) in Ottawa, ON, Canada; and the isolate has been deposited with the Canadian Collection of Fungal Cultures (CCFC). References: (1) S. T. Coates et al. Plant Dis. 78:1153, 1994. (2) O. D. Dhingra and J. B. Sinclair. Page 287 in: Basic Plant Pathology Methods. CRC Press, Inc., Boca Raton, FL, 1985. (3) G. C. Kingsland. Plant Dis. Rep. 47:724, 1963. (4) G. P. Munkvold and C. A. Martinson. Page 6 in: Iowa State University Extension Publication Pm-596, Iowa State University Press, Ames, 1994.

scholarly journals Severity of leaf diseases in maize inbred lines with different kernel hardness in two sowing seasons

2018 ◽  
Vol 39 (1) ◽  
pp. 29
Author(s):  
Cecília Aparecida Spada ◽  
Marcos Ventura Faria ◽  
Marcelo Cruz Mendes ◽  
Welton Luiz Zaluski ◽  
Emanuel Gava ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Inbred Lines ◽  
Gray Leaf Spot ◽  
Leaf Blight ◽  
Kernel Hardness ◽  
Northern Leaf Blight ◽  
Maize Inbred Lines ◽  
Progress Curve ◽  
White Leaf ◽  
Cercospora Zeae Maydis

Resistance of maize inbred lines to major leaf diseases should be characterized for the development of new hybrids in breeding programs. Thus, this study aimed to assess the severity of leaf diseases in maize inbredlines with different kernel hardnessand two sowingseasons. We assessed four inbred lines and one check hybrid with dent kernels and four inbred lines and a check hybrid with flint kernels. Treatments were conducted in two sowing seasons, one in October, and another in December 2013. The symptoms of gray leaf spot (Cercospora zeae-maydis), northern leaf blight (Exserohilum turcicum), and white leaf spot (a complex of Phaeosphaeria maydis and Pantoea ananatis) were assessed every 10 days from flowering. The area under the disease progress curve was also calculated. Severity level of the diseases was higher in inbred lines when compared to the check hybrds (AG8041 PRO and P30R50YH), regardless of kernel hardness. Dent-kernel inbred lines showed a higher severity of northern leaf blight symptoms when compared to flint-kernelones. It is worth mentioning that disease severity increased as sowing was delayed.

scholarly journals Response of maize genotypes to gray leaf spot disease (Cercospora zeae-maydis) in the hills of Nepal

2013 ◽  
Vol 2 ◽  
pp. 93-101 ◽  
Author(s):  
G Manandhar ◽  
GO Ferrara ◽  
TP Tiwari ◽  
S Baidya ◽  
ASR Bajracharya ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Gray Leaf Spot ◽  
Leaf Spot Disease ◽  
Kathmandu Valley ◽  
Research Station ◽  
Maize Genotypes ◽  
Cercospora Zeae Maydis ◽  
Moderately Resistant ◽  
First Time

Gray leaf spot (GLS) is an important and destructive disease of maize in the hills of Nepal. The occurrence of this disease is recorded for the first time in the country in 2006. Several genotypes of maize supposed to be resistant to gray leaf spot in SARMP Zimbabwe and CIAT Colombia were evaluated together with other varieties in observation nursery conducted at farmer’s fields as well as at Khumaltar (NARC research station in the Kathmandu Valley) during 2008 and 2009. Ten out of 28 genotypes of maize were identified as resistant to moderately resistant to GLS. The disease incidence was higher on the open pollinated varieties of maize. The severity of GLS on genotypes of maize observed as 3.0 and 2.2, respectively at Baluwapati and Dhungkharka in Kavrepalanchwok and 2.0 at Khumaltar in Lalitpur during 2008. The severity of GLS was observed as high as 2.4 at Pakhribas in Dhankuta and 1.7 at Khumaltar in 2009. DOI: http://dx.doi.org/10.3126/ajn.v2i0.7524 Agronomy Journal of Nepal (Agron JN) Vol. 2: 2011 pp.93-101

scholarly journals Frequency and Timing of Fungicide Applications for the Control of Gray Leaf Spot in Maize

Plant Disease ◽  
1997 ◽  
Vol 81 (1) ◽  
pp. 41-48 ◽  
Author(s):  
J. M. J. Ward ◽  
M. D. Laing ◽  
F. H. J. Rijkenberg
Keyword(s):  
Leaf Spot ◽  
Logistic Model ◽  
Gray Leaf Spot ◽  
Effective Control ◽  
Physiological Maturity ◽  
Progress Curve ◽  
Cercospora Zeae Maydis ◽  
Yield Responses ◽  
And Control ◽  
Host Development

Timing and frequency of fungicide treatments for management and control of gray leaf spot of maize, caused by Cercospora zeae-maydis, were quantified with the logistic model and area under disease progress curve (AUDPC). Control was most effective when spraying commenced as disease severity levels reached 2 to 3% of the leaf area blighted and when lesions were restricted to the basal five leaves of the maize plant. Highest grain yields were achieved with treatments providing disease control until the crop was physiologically mature. To provide this length of control, the frequency and number of fungicide applications varied with the stage of host development when disease was first apparent; with early infections, more fungicide treatments were necessary to provide protection until physiological maturity. Yield responses to fungicides appeared to be a function of the growth stage of the host when sprays were initiated, the amount of disease at spray date, the length of fungicide control, and effective control through to physiological maturity.

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