scholarly journals Fungicide Sensitivity of Sclerotinia homoeocarpa from Golf Courses in Ohio

Plant Disease ◽  
2006 ◽  
Vol 90 (6) ◽  
pp. 807-813 ◽  
Author(s):  
Young-Ki Jo ◽  
Amy L. Niver ◽  
Joseph W. Rimelspach ◽  
Michael J. Boehm
Keyword(s):  
Field Trials ◽  
In Vitro Assays ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Field Efficacy ◽  
Fungicide Insensitivity

Managing dollar spot, the most common and chronic disease on intensively cultivated turfgrass, relies on the judicious use of fungicides. The heavy use of fungicides has led to the development of isolates of Sclerotinia homoeocarpa insensitive to several classes of fungicides, including benzimidazoles, demethylation-inhibitors, and dicarboximides. In vitro fungicide sensitivity assays using single discriminatory concentrations of thiophanate-methyl, propiconazole, and iprodione were developed in this study for evaluating field efficacy of these fungicides and the prevalence of fungicide insensitivity within S. homoeocarpa isolated from golf courses throughout Ohio. Discriminatory concentrations for these fungicides were determined to be: thiophanate-methyl = 1,000 μg a.i. ml-1, propiconazole = 0.1 μg a.i. ml-1, and iprodione = 1.0 μg a.i. ml-1. Effective concentration that produces 50% inhibition (EC50) was estimated based on relative mycelial growth of S. homoeocarpa on potato dextrose agar (PDA) versus PDA amended with the discriminatory concentration of each fungicide. Field trials conducted at 3 locations in 2002 and 10 locations in 2003 revealed that the in vitro assays accurately predicted field efficacy for thiophanate-methyl. When used to screen 192 S. homoeocarpa isolates collected previously from 55 golf courses throughout Ohio, the in vitro assays revealed that 34 of the golf courses sampled had S. homoeocarpa resistant to thiophanate-methyl. S. homoeocarpa with reduced in vitro sensitivities was isolated from 18 and 1 golf courses for propiconazole and iprodione, respectively.

scholarly journals In Vitro Fungicide-Insensitive Profiles of Sclerotinia homoeocarpa Populations from Pennsylvania and the Surrounding Region

Plant Disease ◽  
2019 ◽  
Vol 103 (2) ◽  
pp. 214-222 ◽  
Author(s):  
Cameron M. Stephens ◽  
John Kaminski
Keyword(s):  
Active Ingredient ◽  
Golf Course ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Thiophanate Methyl ◽  
Surrounding Areas ◽  
Fungicide Insensitivity ◽  
Research Facilities

Repeated fungicide applications are typically required to provide adequate control of dollar spot on golf courses and may shift Sclerotinia homoeocarpa populations from sensitive to insensitive or resistant to an active ingredient. The objective of this study was to characterize the geographic distribution of fungicide-insensitive, fungicide-resistant, and multiple fungicide insensitive (MFI) S. homoeocarpa populations on golf courses in Pennsylvania and the surrounding region. S. homoeocarpa isolates (n = 681) were collected from 45 different golf courses or research facilities. Each isolate was evaluated in vitro against propiconazole, iprodione, boscalid, and thiophanate-methyl using discriminatory concentrations of 0.1, 1.0, 1,000, and 1,000 µg of active ingredient per milliliter of PDA, respectively. Relative mycelial growth (RMG) values were used to determine sensitivity or insensitivity based on comparison with a baseline population. Of the 681 isolates evaluated, 81, 80, and 85% exhibited reduced sensitivity to boscalid, iprodione, and propiconazole, respectively. A total of 41% of the isolates were resistant to thiophanate-methyl. Based on mean RMG of all isolates from each golf course, 16, 35, and 37 of the 45 golf courses exhibited reduced sensitivity to boscalid, iprodione, and propiconazole, respectively. A total of 585 isolates (86%) exhibited an MFI profile in which they were insensitive or resistant to at least two fungicides evaluated. Isolates with reduced sensitivity to boscalid, iprodione, and propiconazole, but sensitive to thiophanate-methyl, were the most common phenotype within the three-MFI profile. Fungicide insensitivity and resistance to commonly used fungicides, as well as MFI profiles, were prevalent in Pennsylvania and the surrounding areas and may cause management challenges.

scholarly journals Geographic Distribution of Fungicide-Insensitive Sclerotinia homoeocarpa Isolates from Golf Courses in the Northeastern United States

Plant Disease ◽  
2010 ◽  
Vol 94 (2) ◽  
pp. 186-195 ◽  
Author(s):  
Alexander I. Putman ◽  
Geunhwa Jung ◽  
John E. Kaminski
Keyword(s):  
United States ◽  
Resistance Mechanisms ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Northeastern United States ◽  
Fungicide Sensitivity ◽  
Putting Greens ◽  
Thiophanate Methyl

Chemical management of dollar spot in turf may lead to the development of Sclerotinia homoeocarpa populations with reduced fungicide sensitivity. The objective of this study was to determine the scope of S. homoeocarpa insensitivity to fungicides commonly used to control dollar spot on golf courses in the northeastern United States. A total of 965 and 387 isolates of S. homoeocarpa from intensively or individually sampled sites, respectively, were evaluated for in vitro sensitivity to iprodione, propiconazole, and thiophanate-methyl. Mean baseline sensitivities to iprodione and propiconazole were 0.2763 and 0.0016 μg a.i. ml–1, respectively, and all baseline isolates were sensitive to thiophanate-methyl at 1,000 μg a.i. ml–1. When compared with the baseline population, 14 and 18 of 20 total populations were less sensitive to iprodione and propiconazole, respectively. Individually sampled isolates obtained from fairways, putting greens, or tees were less sensitive to iprodione and propiconazole when compared with the baseline. For thiophanate-methyl, five populations were sensitive, six were resistant, and the remaining nine populations contained various proportions (2 to 92%) of resistant isolates. Individually sampled isolates obtained from fairways and putting greens were evaluated for associations in sensitivity among the three fungicides. A weak but positive correlation in sensitivity to iprodione and propiconazole was observed for isolates resistant to thiophanate-methyl but correlations for sensitive isolates were not significant. Furthermore, isolates with highly reduced sensitivity to iprodione clustered in a narrow range of propiconazole sensitivity. These data suggest the possible existence of resistance mechanisms common to diverse fungicide classes. Overall, results indicate that insensitivity of S. homoeocarpa to iprodione, propiconazole, and thiophanate-methyl exists in varying degrees on golf courses in the northeastern United States.

scholarly journals Control of Dollar Spot of Creeping Bentgrass Caused by an Isolate of Sclerotinia homoeocarpa Resistant to Benzimidazole and Demethylation-Inhibitor Fungicides

Plant Disease ◽  
1997 ◽  
Vol 81 (11) ◽  
pp. 1259-1263 ◽  
Author(s):  
L. L. Burpee
Keyword(s):  
Incubation Period ◽  
Field Tests ◽  
Creeping Bentgrass ◽  
Disease Suppression ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Demethylation Inhibitor

The effects of fungicides were studied on two isolates of Sclerotinia homoeocarpa that differed in fungicide sensitivity. Concentrations of benzimidazole (benomyl and thiophanate-methyl), demethylation inhibitor (fenarimol, propiconazole, and triadimefon), and nitrile (chlorothalonil) fungicides required to inhibit mycelial growth in vitro by 50 and 90% (effective concentration; EC50,90) were significantly greater for isolate S088 than for isolate S084. No differences were observed in the EC50,90 values of a pyridylaniline (fluazinam) or dicarboximide (iprodione) fungicide. In field tests conducted on creeping bentgrass, S088 had a significantly shorter incubation period than S084 in plots treated with propiconazole applied at 0.2 or 0.8 kg a.i. ha-1 in 1994 or 0.4 kg a.i. ha-1 in 1995, thiophanate-methyl applied at 1.5 or 3.0 kg a.i. ha-1 in 1994 and 1995, or a tank-mix of propiconazole and iprodione applied at 1.6 + 0.8 kg a.i. ha-1 in 1994. No differences in incubation periods occurred in plots treated with chlorothalonil or iprodione in either year, or with fluazinam in 1995 and 1996. Fewer days were required to reach 5% disease severity in turf inoculated with isolate S088, compared to isolate S084, in plots treated with propiconazole, thiophanate-methyl, or certain tank-mixes containing propiconazole, in 1994 and 1995. Several treatments, including propiconazole, thiophanate-methyl, and fluazinam, resulted in suppression of disease caused by isolate S084 to less than 5% severity for more than 21 days, while only fluazinam applied at 1.6 or 3.2 kg a.i. ha-1 provided more than 21 days of disease suppression in turf inoculated with either of the isolates tested. Slope coefficients from linear regressions between incubation period or days to 5% disease and concentrations of fungicide applied in 1996 were significantly different for isolate S084 compared to isolate S088 in plots treated with propiconazole, but not in plots treated with fluazinam.

scholarly journals The Association Between In Vitro Propiconazole Sensitivity and Field Efficacy of Five New England Sclerotinia homoeocarpa Populations

Plant Disease ◽  
2012 ◽  
Vol 96 (4) ◽  
pp. 552-561 ◽  
Author(s):  
James T. Popko ◽  
Chang-Ho Ok ◽  
Katie Campbell-Nelson ◽  
Geunhwa Jung
Keyword(s):  
New England ◽  
Field Resistance ◽  
Golf Club ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Mycelium Growth ◽  
Turfgrass Disease ◽  
Country Club ◽  
Field Efficacy

Dollar spot (Sclerotinia homoeocarpa) is a major turfgrass disease requiring fungicide application to maintain acceptable conditions for golf. A 2-year field experiment was conducted to determine the association between field efficacy of propiconazole and in vitro fungicide sensitivity of isolates from five S. homoeocarpa populations. Four golf courses with prior propiconazole exposure (Hartford Golf Club, Hickory Ridge Country Club, Shuttle Meadow Country Club, and Wintonbury Hills Golf Club), and a baseline site with no prior propiconazole exposure (Joseph Troll Turf Research Facility) were chosen as field sites. Experimental plots at each site received the following treatments at 21-day intervals: untreated, propiconazole (0.44, 0.88, 1.32, and 1.76 kg a.i. ha–1), and chlorothalonil (8.18 kg a.i. ha–1). S. homoeocarpa isolates were sampled at three time points during 2009 and 2010: initial (directly before fungicide treatment), 7 days after treatment (DAT), and 21 days after the last treatment. Isolates sampled from dollar spot infection centers at 7 DAT (2009 and 2010) were considered to exhibit “practical field resistance”. In parallel, S. homoeocarpa isolates from each site were assayed for in vitro sensitivity to propiconazole by determining relative mycelium growth percentages (RMG%) on potato dextrose agar amended with propiconazole at a discriminatory concentration of 0.1 μg a.i. ml–1. S. homoeocarpa isolates from the four exposed populations displayed significantly higher RMG% values than the baseline population. In general, field efficacy at all propiconazole rates tested was lower at the four locations with prior propiconazole exposure when compared with the baseline population. Increased RMG% values on the propiconazole discriminatory concentration 0.1 μg a.i. ml–1 were associated with decreased relative control values for all propiconazole rates in 2009 and 2010. Results suggest RMG values above 50% at the propiconazole discriminatory concentration of 0.1 μg a.i. ml–1 may be a suitable threshold for detection of S. homoeocarpa isolates that cause practical DMI field resistance.

scholarly journals Relationship Between Fungicide Sensitivity and Control of Gummy Stem Blight of Watermelon Under Field Conditions

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1780-1784 ◽  
Author(s):  
A. Thomas ◽  
D. B. Langston ◽  
H. F. Sanders ◽  
K. L. Stevenson
Keyword(s):  
Fungicide Resistance ◽  
Field Experiments ◽  
In Vitro Assays ◽  
Didymella Bryoniae ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
And Control

Gummy stem blight (GSB), caused by the fungus Didymella bryoniae, is the most destructive disease of watermelon and is managed primarily with fungicides. D. bryoniae has developed resistance to many fungicides that were once very effective, including azoxystrobin, boscalid, and thiophanate-methyl. Field experiments were conducted in Tifton (TN) and Reidsville (RV), GA in 2009 and 2010 to establish a relationship between frequency of resistance to a fungicide based on in vitro assays and its efficacy in the management of GSB. Frequency of resistance to boscalid, thiophanate-methyl, and azoxystrobin was >0.80 in isolates collected from nontreated plots in both locations and years. All isolates collected after six applications of boscalid, thiophanate-methyl, or azoxystrobin were resistant to the respective fungicide. All isolates collected from treated and nontreated plots were sensitive to tebuconazole and difenoconazole. GSB severity was assessed on a weekly basis from 63 days after planting. GSB severity in plots treated with boscalid, thiophanate-methyl, or azoxystrobin was not significantly different from that in the nontreated plots (39%, TN-2009; 45%, TN-2010; and 16%, RV-2010). GSB severity in tebuconazole-treated plots (27%, TN-2009; 14%, TN-2010; and 4%, RV-2010) was significantly lower than all other treatments and the nontreated control. There was a consistent negative association between frequency of fungicide resistance and disease control in the field. Thus, knowledge of the frequency of fungicide resistance in the pathogen population will be helpful in selecting the most effective fungicides for the management of GSB in watermelon fields.

scholarly journals Thiophanate-Methyl and Propiconazole Sensitivity in Sclerotinia homoeocarpa Populations from Golf Courses in Wisconsin and Massachusetts

Plant Disease ◽  
2009 ◽  
Vol 93 (1) ◽  
pp. 100-105 ◽  
Author(s):  
Paul L. Koch ◽  
Craig R. Grau ◽  
Young-Ki Jo ◽  
Geunhwa Jung
Keyword(s):  
Golf Course ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Putting Greens ◽  
Thiophanate Methyl ◽  
Development Of Resistance ◽  
History Of ◽  
Intensively Managed ◽  
Pathogen Populations

Management of dollar spot, caused by the fungus Sclerotinia homoeocarpa, is dependent upon repeated fungicide applications in intensively managed turfgrass such as golf course putting greens and fairways. Repeated fungicide applications could potentially select for fungicide-resistant isolates and result in a reduction of disease control. The objectives of this study were to determine the degree of S. homoeocarpa in vitro sensitivity to the fungicides thiophanate-methyl and propiconazole using isolates collected from golf course putting greens, fairways, and roughs; and to determine the relationships of golf course age and fungicide history to the frequency of fungicide-insensitive isolates within the population. More than 1,400 S. homoeocarpa isolates were collected from putting greens, fairways, and roughs at six Wisconsin golf courses and one Massachusetts golf course and subjected to in vitro fungicide sensitivity assays with single discriminatory concentrations of thiophanate-methyl and propiconazole. Five of seven pathogen populations from rough areas were not significantly different from one another in propiconazole sensitivity. These populations were collectively the most sensitive to both fungicides and therefore, served as baseline populations for comparison with fungicide-exposed populations from putting greens and fairways. Greater propiconazole insensitivity was observed in populations collected from fairways and putting greens that received more frequent applications of the fungicide than those isolated from the roughs. In nearly all the golf courses, the frequency of thiophanate-methyl insensitivity was higher among isolates of S. homoeocarpa collected from fairways than from roughs regardless of the age of the golf course or history of benzimidazole use. Thus, while the development of resistance to propiconazole can be predicted in part by the relative frequency of demethylation inhibitor fungicide applications, the occurrence of populations resistant to thiophanate-methyl appears to be unrelated to recent use of the benzimidazole class of fungicides.

scholarly journals Evaluation of a Sclerotinia homoeocarpa Population with Multiple Fungicide Resistance Phenotypes Under Differing Selection Pressures

Plant Disease ◽  
2019 ◽  
Vol 103 (4) ◽  
pp. 685-690 ◽  
Author(s):  
Hyunkyu Sang ◽  
James T. Popko ◽  
Geunhwa Jung
Keyword(s):  
Fungicide Resistance ◽  
The United States ◽  
Golf Courses ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Selection Pressures ◽  
Effective Strategies ◽  
Benzimidazole Resistance ◽  
Dicarboximide Resistance

Dollar spot, caused by Sclerotinia homoeocarpa, is one of the most significant diseases of cool-season turfgrass on golf courses. Resistance to the benzimidazole, dicarboximide, and succinate dehydrogenase inhibitor (SDHI) classes and reduced sensitivity to the sterol-demethylation inhibitor (DMI) in S. homoeocarpa populations have been widely reported in the United States. Moreover, the occurrence of S. homoeocarpa populations with multiple fungicide resistance (MFR) is a growing problem on golf courses. The present study was undertaken to evaluate the efficacy of DMI, dicarboximide, and SDHI against a S. homoeocarpa population with MFR on a Connecticut golf course fairway from 2014 to 2016. Also, because the S. homoeocarpa population consisted of four different phenotypes with differing resistance profiles to benzimidazole, dicarboximide, and DMI, in vitro sensitivity assays were used to understand the dynamics of the MFR population in the presence and absence of fungicide selection pressures. Results indicated that boscalid fungicide (SDHI) was able to provide an acceptable control of the MFR dollar spot population. Propiconazole or iprodione application selected isolates with both DMI and dicarboximide resistance (DMI-R/Dicar-R). In the absence of fungicide selection pressures, the percent frequency of DMI-R/Dicar-R or DMI and benzimidazole resistance (DMI-R/Ben-R) isolates declined in the population. Out of the four phenotypes, the percent frequency of isolates with DMI, dicarboximide, and benzimidazole resistance (DMI-R/Dicar-R/Ben-R) was the lowest in the population regardless of fungicide selection pressures. Our first report of MFR population dynamics will help develop effective strategies for managing MFR and potentially delay the emergence of future resistant populations in S. homoeocarpa.

scholarly journals Rapid Development of Fungicide Resistance by Sclerotinia homoeocarpa on Turfgrass

2008 ◽  
Vol 98 (12) ◽  
pp. 1297-1304 ◽  
Author(s):  
Young-Ki Jo ◽  
Seog Won Chang ◽  
Michael Boehm ◽  
Geunhwa Jung
Keyword(s):  
Fungicide Resistance ◽  
Rapid Development ◽  
Management Strategies ◽  
Research Field ◽  
Population Diversity ◽  
Sclerotinia Homoeocarpa ◽  
Dollar Spot ◽  
Thiophanate Methyl ◽  
Putting Green

Dollar spot, caused by Sclerotinia homoeocarpa, is the most prevalent and economically important turfgrass disease in North America. Increasing levels of fungicide resistance, coupled with tightening environmental scrutiny of existing fungicides, has left fewer options for managing dollar spot. More knowledge about S. homoeocarpa populations is needed to improve dollar spot management strategies, especially with respect to minimizing the development of fungicide resistance. Population diversity of S. homoeocarpa was examined using inter-simple sequence repeat markers and vegetative compatibility assays. Two subgroups were found in S. homoeocarpa field populations on both fairway and putting green turfgrass at a research field in Wisconsin. These subgroups were genetically different, vegetatively incompatible, and had different fungicide sensitivities. The frequency of the two genetic subgroups differed significantly between the fairway and putting green, but was uniform within the fairway or within the green. Population dynamics of S. homoeocarpa in response to two systemic fungicides (thiophanate-methyl and propiconazole) were assessed based on in vitro fungicide sensitivity. Dynamics of S. homoeocarpa populations depended on the presence of fungicide-resistant isolates in the initial populations before fungicide applications and changed rapidly after fungicide applications. Shifting of the population toward propiconazole resistance was gradual, whereas thiophanate-methyl resistance developed rapidly in the population. In conclusion, field populations of S. homoeocarpa containing genetically distinct, vegetatively incompatible groups were different on turfgrass that was managed differently, and they were changed rapidly after exposure to fungicides.

scholarly journals Resistance of Kansas Sclerotinia homoeocarpa Isolates to Thiophanate-Methyl and Determination of Associated β-Tubulin Mutation

2014 ◽  
Vol 15 (2) ◽  
pp. 80-84 ◽  
Author(s):  
Jesse C. Ostrander ◽  
Richard B. Todd ◽  
Megan M. Kennelly
Keyword(s):  
Golf Course ◽  
Sclerotinia Homoeocarpa ◽  
Fungicide Sensitivity ◽  
Putting Greens ◽  
Thiophanate Methyl ◽  
In Vitro Sensitivity ◽  
Starting Point ◽  
Β Tubulin

Eighty-two isolates of Sclerotinia homoeocarpa from 12 sites in Kansas were evaluated for in vitro sensitivity to the methyl benzimidazole carbamate (MBC) fungicide thiophanate-methyl at the discriminatory dose of 10 μg/ml. Seventeen isolates were sensitive to thiophanate-methyl and the remaining isolates were resistant. Of the 65 isolates from golf course putting greens, two isolates were sensitive and the remaining 63 isolates were resistant. Six resistant and five sensitive isolates were also evaluated in greenhouse assays on fungicide-treated plants. The isolates that were sensitive to thiophanate-methyl in vitro did not cause any disease on thiophanate-methyl-treated plants, and those that were resistant in vitro caused blighting on treated plants equivalent to the nontreated controls. The entire β-tubulin gene was sequenced for four resistant and four sensitive isolates. The resistant isolates all harbored a substitution of alanine for glutamic acid at codon 198 (E198A). These results provide a starting point for further surveys and monitoring of fungicide sensitivity. Accepted 7 April 2014. Published 6 June 2014.

scholarly journals In Vitro and in Field Response of Different Fungicides against Aspergillus flavus and Fusarium Species Causing Ear Rot Disease of Maize

Toxins ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 11 ◽  
Author(s):  
Mario Masiello ◽  
Stefania Somma ◽  
Veronica Ghionna ◽  
Antonio Francesco Logrieco ◽  
Antonio Moretti
Keyword(s):  
Aspergillus Flavus ◽  
Fusarium Species ◽  
Field Trials ◽  
Fungal Species ◽  
In Vitro Assays ◽  
Ear Rot ◽  
Thiophanate Methyl ◽  
Toxigenic Fungi ◽  
Rot Disease

Aspergillus flavus, the main aflatoxin B1 producing fungal species, Fusarium graminearum, a deoxynivalenol producer, and the fumonisin-producing species F. proliferatum and F. verticillioides are the main toxigenic fungi (TF) that colonize maize. Several strategies are available to control TF and related mycotoxins, such as chemical control. However, there is poor knowledge on the efficacy of fungicides on maize plants since few molecules are registered. The sensitivity of F. graminearum, F. proliferatum, F. verticillioides, and A. flavus to eleven fungicides, selected based on their different modes of action, was evaluated in both in vitro assays and, after selection, in the field. In vitro, demethylation inhibitors (DMI) showed excellent performances, followed by thiophanate-methyl and folpet. Among the succinate dehydrogenase inhibitors (SDHI), isopyrazam showed a higher effectiveness against Fusarium species than boscalid, which was ineffective against Fusarium, like the phenyl-pyrrole fludioxonil. Furthermore, both SDHIs and fludioxonil were more active against A. flavus than Fusarium species. In field trials, prothioconazole and thiophanate-methyl were confirmed to be effective to reduce F. graminearum (52% and 48%) and F. proliferatum contamination (44% and 27%). On the other hand, prothioconazole and boscalid could reduce A. flavus contamination at values of 75% and 56%, respectively.

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