scholarly journals First Report of Resistance to Cyflufenamid in Podosphaera xanthii, Causal Agent of Powdery Mildew, from Melon and Zucchini Fields in Italy

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1581-1581 ◽  
Author(s):  
A. Pirondi ◽  
I. M. Nanni ◽  
A. Brunelli ◽  
M. Collina
Keyword(s):  
Powdery Mildew ◽  
Fungicide Resistance ◽  
Management Strategies ◽  
Resistance Management ◽  
Personal Communication ◽  
Causal Agent ◽  
Infected Leaf ◽  
Podosphaera Xanthii ◽  
Growing Seasons ◽  
Action Committee

The fungicide cyflufenamid (phenyl-acetamide, Fungicide Resistance Action Committee [FRAC] code U6) was approved for use in Italy in 2011 as Takumi (Certis Europe, Utrecht, The Netherlands) to control Podosphaera xanthii (Castagne) U. Braun. & N. Shishkoff, the main causal agent of cucurbit powdery mildew. Considering that strains of this pathogen have developed resistance to strobilurin (5) and demethylation inhibitor (DMI) (4) fungicides, cyflufenamid represented a viable alternative to control this disease. However, this fungicide is also prone to resistance development as illustrated by resistance of P. xanthii in Japan (3). In the 2012 and 2013 growing seasons, significant declines in cyflufenamid efficacy were observed in two experimental fields in the Apulia (AP) and Emilia-Romagna (ER) regions of Italy on Cucumis melo and Cucurbita pepo, respectively. Takumi had been applied four times at the recommended field rate of 0.15 liter/ha (15 μg/ml of active ingredient [a.i.]) each growing season since 2010 in each field. Powdery mildew-infected leaf samples were collected in 2012 from both fields (25 isolates from AP and 19 from ER), and from five gardens (one isolate per garden); while in 2013, samples were collected only from the ER field (two polyconidial isolates). Isolates were maintained on detached zucchini cotyledons (1). Sensitivity of the isolates to cyflufenamid was determined by leaf disk bioassays (4) using Takumi at 0.01, 0.1, 1, 10, 20, and 50 μg a.i./ml. The 50% effective concentration (EC50) and the minimum inhibitory concentration (MIC) values were calculated (2). Isolates collected in ER and the gardens in 2012 all had an EC50< 0.01 μg/ml, and the MIC ranged from <0.01 to <1 μg/ml. Isolates from AP in 2012 had elevated EC50 values, from 0.230 to >50 μg/ml, and MIC values from <10 to >50 μg/ml; by 2013, the EC50 values of ER isolates ranged from 3.35 to >50 μg/ml. Based on the mean EC50 value of 0.0019 μg/ml for sensitive isolates of P. xanthii in Japan (2), isolates from both the ER field and gardens in 2012 were considered sensitive to cyflufenamid. Additionally, EC50 values of AP isolates from 2012 and ER isolates from 2013 were greater than those of sensitive isolates, indicating a shift in sensitivity toward resistance to cyflufenamid (resistance factor >100 [2]). Consequently, poor control of powdery mildew with cyflufenamid applications in the AP and ER trials was most likely a result of fungicide resistance. Isolates from these fields were exposed to selection pressure for fungicide resistance because cyflufenamid was applied more times than permitted in the label instructions. However, control of powdery mildew in 2013 was not as effective as in previous years in commercial fields in AP (C. Dongiovanni, personal communication). This observation, combined with proof of reduced sensitivity of some P. xanthii strains in Italy to cyflufenamid, highlights the need for implementing resistance management strategies to minimize the risk of fungicide resistant strains developing in cucurbit fields. References: (1) B. Álvarez and J. A. Torés. Bol. San. Veg. Plagas 23:283, 1997. (2) M. Haramoto et al. J. Pest. Sci. 31:397, 2006. (3) H. Hosokawa et al. Jpn. J. Phytopathol. 72:260, 2006. (4) M. T. McGrath et al. Plant Dis. 80:697, 1996. (5) M. T. McGrath and N. Shishkoff. Plant. Dis. 87:1007, 2003.

First Report of Resistance to Boscalid in Podosphaera xanthii, Cucurbit Powdery Mildew, in South Carolina

2018 ◽  
Vol 19 (3) ◽  
pp. 220-221 ◽  
Author(s):  
Anthony P. Keinath ◽  
Gabriel Rennberger ◽  
Chandrasekar S. Kousik
Keyword(s):  
South Carolina ◽  
Powdery Mildew ◽  
Fungicide Resistance ◽  
Southern United States ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
Action Committee ◽  
Summer Squash ◽  
Laboratory Bioassays ◽  
Cucurbit Powdery Mildew

Resistance to boscalid, one of the older succinate-dehydrogenase inhibitors (SHDI) in Fungicide Resistance Action Committee (FRAC) code 7, was detected in Podosphaera xanthii, the cucurbit powdery mildew fungus, in South Carolina in July 2017. Resistance to the field rate (682 ppm) of boscalid was confirmed in greenhouse experiments and laboratory bioassays conducted on summer squash plants and cotyledons, respectively, that had been treated with a range of boscalid concentrations. This report is the first documentation of resistance to boscalid in P. xanthii in the southern United States.

scholarly journals Fungicide Resistance Management Guidelines for Cucurbit Downy and Powdery Mildew Control in the Mid-Atlantic and Northeast Regions of the United States in 2018

2018 ◽  
Vol 19 (1) ◽  
pp. 34-36
Author(s):  
Christian A. Wyenandt ◽  
Margaret T. McGrath ◽  
Kathryne L. Everts ◽  
Steven L. Rideout ◽  
Beth K. Gugino ◽  
...  
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Fungicide Resistance ◽  
Resistance Management ◽  
The United States ◽  
Vegetable Crops ◽  
Fresh Market ◽  
Control Programs ◽  
Action Committee ◽  
Unites States

In the mid-Atlantic and Northeast regions of the United States, more than 163,000 acres of fresh-market vegetable crops are grown annually. Two important diseases of cucurbit crops across the Unites States and world are powdery mildew caused by Podosphaera xanthii (formerly Sphaerotheca fuliginea [Schlecht ex Fr.] Poll.) and downy mildew caused by Pseudoperonospora cubensis. Resistance to a number of high-risk fungicides has been detected in both pathogens. To help cucurbit growers in the mid-Atlantic and Northeast regions properly manage both diseases, an updated fungicide resistance management table has been developed to promote the importance of understanding Fungicide Resistance Action Committee (FRAC) codes. This table provides a tool to allow cucurbit growers to develop season-long cucurbit downy and powdery mildew control programs.

scholarly journals Fungicide Resistance Management Guidelines for the Control of Tomato Diseases in the Mid-Atlantic and Northeast Regions of the United States

2010 ◽  
Vol 11 (1) ◽  
pp. 32 ◽  
Author(s):  
Christian A. Wyenandt ◽  
Steven L. Rideout ◽  
Beth K. Gugino ◽  
Margaret T. McGrath ◽  
Kathryne L. Everts ◽  
...  
Keyword(s):  
United States ◽  
Fungicide Resistance ◽  
Resistance Management ◽  
The United States ◽  
Management Tool ◽  
Fresh Market ◽  
Management Guidelines ◽  
Control Programs ◽  
Action Committee ◽  
Tomato Diseases

Foliar diseases and fruit rots occur routinely on tomato, an important crop grown throughout the Mid-Atlantic and Northeast regions of the United States where it is produced for both fresh-market and processing. To enable these tomato growers to more effectively manage economically important diseases, a fungicide resistance management table has been developed which promotes the importance of understanding FRAC (Fungicide Resistance Action Committee) codes and provides an integrated pest management tool for tomato growers which will allow them to develop season-long disease control programs with an emphasis on fungicide resistance management. Accepted for publication 19 July 2010. Published 27 August 2010.

scholarly journals Succinate dehydrogenase inhibitor (SDHI) fungicide resistance prevention strategy

2011 ◽  
Vol 64 ◽  
pp. 119-124 ◽  
Author(s):  
A.H. McKay ◽  
G.C. Hagerty ◽  
G.B. Follas ◽  
M.S. Moore ◽  
M.S. Christie ◽  
...  
Keyword(s):  
New Zealand ◽  
High Risk ◽  
Succinate Dehydrogenase ◽  
Fungicide Resistance ◽  
Fungal Pathogens ◽  
Resistance Management ◽  
Resistance Development ◽  
Development Of Resistance ◽  
Action Committee ◽  
Succinate Dehydrogenase Inhibitor

Succinate dehydrogenase inhibitor (SDHI) fungicides are currently represented in New Zealand by eight active ingredients bixafen boscalid carboxin fluaxapyroxad fluopyram isopyrazam penthiopyrad and sedaxane They are either currently registered or undergoing development in New Zealand for use against a range of ascomycete and basiodiomycete pathogens in crops including cereals ryegrass seed apples pears grapes stonefruit cucurbits and kiwifruit These fungicides are considered to have medium to high risk of resistance development and resistance management is recommended by the Fungicide Resistance Action Committee (FRAC) in Europe Guidelines are presented for use of SDHI fungicides in New Zealand to help avoid or delay the development of resistance in the fungal pathogens that they target

scholarly journals Fungicide resistance characterised across seven chemical classes in a Botrytis cinerea population isolated from Australian vineyards

2021 ◽  
Author(s):  
Lincoln A. Harper ◽  
Scott Paton ◽  
Barbara Hall ◽  
Suzanne McKay ◽  
Richard P. Oliver ◽  
...  
Keyword(s):  
Adverse Effect ◽  
Botrytis Cinerea ◽  
Fungicide Resistance ◽  
Chemical Control ◽  
Management Strategies ◽  
Resistance Management ◽  
Gray Mold ◽  
Chemical Groups ◽  
Important Disease ◽  
Selection Of

AbstractGray mold, caused by Botrytis cinerea, is an economically important disease of grapes in Australia and across grape growing regions worldwide. Control of this disease relies heavily on canopy management and the application of single site fungicides. Fungicide application can lead to the selection of fungicide resistant B. cinerea populations, which has an adverse effect on the chemical control of the disease. Characterising the distribution and severity of resistant B. cinerea populations is needed to inform resistance management strategies. In this study, 725 isolates were sampled from 75 Australian vineyards during 2013 – 2016 and were screened against seven fungicides with different MOAs. The resistance frequencies for azoxystrobin, boscalid, fenhexamid, fludioxonil, iprodione, pyrimethanil and tebuconazole were 5, 2.8, 2.1, 6.2, 11.6, 7.7 and 2.9% respectively. Nearly half of the resistant isolates (43.7%) were resistant to more than one of the fungicides tested. The frequency of vineyards with at least one isolate simultaneously resistant to 1, 2, 3, 4 or 5 fungicides was 19.5, 7.8, 6.5, 10.4 and 2.6%.Resistance was associated with previously published genotypes in CytB (G143A), SdhB (H272R/Y), Erg27 (F412S), Mrr1 (D354Y), Os1 (I365S, N373S + Q369P, I365S + D757N) and Pos5 (P319A, L412F). Expression analysis was used to characterise fludioxonil resistant isolates exhibiting overexpression (6.3 - 9.6-fold) of the ABC transporter encoded by AtrB (MDR1 phenotype). Novel genotypes were also described in Mrr1 (S611N, D616G) and Cyp51 (P357S). Resistance frequencies were lower when compared to most previously published surveys of both grape and non-grape B. cinerea resistance. Nonetheless, continued monitoring of critical chemical groups used in Australian vineyards is recommended.

scholarly journals Mixtures as a Fungicide Resistance Management Tactic

2014 ◽  
Vol 104 (12) ◽  
pp. 1264-1273 ◽  
Author(s):  
Frank van den Bosch ◽  
Neil Paveley ◽  
Femke van den Berg ◽  
Peter Hobbelen ◽  
Richard Oliver
Keyword(s):  
At Risk ◽  
Disease Control ◽  
Fungicide Resistance ◽  
Management Strategies ◽  
Resistance Management ◽  
Relative Effect ◽  
Resistance Evolution ◽  
Modes Of Action ◽  
Selection For ◽  
Effective Life

We have reviewed the experimental and modeling evidence on the use of mixtures of fungicides of differing modes of action as a resistance management tactic. The evidence supports the following conclusions. 1. Adding a mixing partner to a fungicide that is at-risk of resistance (without lowering the dose of the at-risk fungicide) reduces the rate of selection for fungicide resistance. This holds for the use of mixing partner fungicides that have either multi-site or single-site modes of action. The resulting predicted increase in the effective life of the at-risk fungicide can be large enough to be of practical relevance. The more effective the mixing partner (due to inherent activity and/or dose), the larger the reduction in selection and the larger the increase in effective life of the at-risk fungicide. 2. Adding a mixing partner while lowering the dose of the at-risk fungicide reduces the selection for fungicide resistance, without compromising effective disease control. The very few studies existing suggest that the reduction in selection is more sensitive to lowering the dose of the at-risk fungicide than to increasing the dose of the mixing partner. 3. Although there are very few studies, the existing evidence suggests that mixing two at-risk fungicides is also a useful resistance management tactic. The aspects that have received too little attention to draw generic conclusions about the effectiveness of fungicide mixtures as resistance management strategies are as follows: (i) the relative effect of the dose of the two mixing partners on selection for fungicide resistance, (ii) the effect of mixing on the effective life of a fungicide (the time from introduction of the fungicide mode of action to the time point where the fungicide can no longer maintain effective disease control), (iii) polygenically determined resistance, (iv) mixtures of two at-risk fungicides, (v) the emergence phase of resistance evolution and the effects of mixtures during this phase, and (vi) monocyclic diseases and nonfoliar diseases. The lack of studies on these aspects of mixture use of fungicides should be a warning against overinterpreting the findings in this review.

scholarly journals Point Mutations in the β-Tubulin of Phytophthora sojae Confer Resistance to Ethaboxam

2019 ◽  
Vol 109 (12) ◽  
pp. 2096-2106 ◽  
Author(s):  
Qin Peng ◽  
Zhiwen Wang ◽  
Yuan Fang ◽  
Weizhen Wang ◽  
Xingkai Cheng ◽  
...  
Keyword(s):  
Fungicide Resistance ◽  
Germination Rate ◽  
Management Strategies ◽  
Resistance Management ◽  
Point Mutations ◽  
Phytophthora Sojae ◽  
Cross Resistance ◽  
Baseline Sensitivity ◽  
Resistant Mutants ◽  
Β Tubulin

Ethaboxam is a β-tubulin inhibitor registered for the control of oomycete pathogens. The current study was established to determine the ethaboxam sensitivity of the plant pathogen Phytophthora sojae and investigate the potential for the emergence of fungicide resistance. The effective concentration for 50% inhibition (EC50) of 112 Phytophthora sojae isolates exhibited a unimodal distribution with a mean EC50 for ethaboxam of 0.033 µg/ml. Establishing this baseline sensitivity provided critical data for monitoring changes in ethaboxam-sensitivity in field populations. The potential for fungicide resistance was investigated using adaptation on ethaboxam-amended V8 agar, which resulted in the isolation of 20 resistant mutants. An assessment of the biological characteristics of the mutants including mycelial growth, sporulation, germination rate and pathogenicity indicated that the resistance risk in Phytophthora sojae was low to medium with no cross-resistance between ethaboxam and cymoxanil, metalaxyl, flumorph, and oxathiapiprolin being detected. However, positive cross-resistance was found between ethaboxam and zoxamide for Q8L and I258V but negative cross-resistance for C165Y. Further investigation revealed that the ethaboxam-resistant mutants had point mutations at amino acids Q8L, C165Y, or I258V of their β-tubulin protein sequences. CRISPR/Cas9-mediated transformation experiments confirmed that the Q8L, C165Y, or I258V mutations could confer ethaboxam resistance in Phytophthora sojae and that the C165Y mutation induces high levels of resistance. Taken together, the results of the study provide essential data for monitoring the emergence of resistance and resistance management strategies for ethaboxam, as well as for improving the design of novel β-tubulin inhibitors for future development.

scholarly journals Strobilurin (QoI) Resistance in Populations of Erysiphe necator on Grapes in Michigan

Plant Disease ◽  
2012 ◽  
Vol 96 (11) ◽  
pp. 1621-1628 ◽  
Author(s):  
L. A. Miles ◽  
T. D. Miles ◽  
W. W. Kirk ◽  
A. M. C. Schilder
Keyword(s):  
Powdery Mildew ◽  
Fungicide Resistance ◽  
Resistance Management ◽  
The United States ◽  
Suboptimal Control ◽  
Single Nucleotide ◽  
Erysiphe Necator ◽  
Nucleotide Mutation ◽  
Conidium Germination ◽  
Qoi Resistance

Powdery mildew, caused by Erysiphe necator, is the most common and destructive disease of grapes (Vitis spp.) worldwide. In Michigan, it is primarily controlled with fungicides, including strobilurins (quinone outside inhibitors [QoIs]). Within the United States, resistance to this class of fungicides has been reported in E. necator populations in some east coast states. Among 12 E. necator isolates collected from five Michigan vineyards in 2008, one carried the G143A single-nucleotide mutation responsible for QoI resistance. This isolate was confirmed to be resistant in a conidium germination assay on water agar amended with trifloxystrobin at 0.001, 0.01, 0.1, 1, 10, or 100 μg/ml and salicylhydroxamic acid (100 mg/liter). The mutant isolate was able to germinate on media amended with 100 μg/ml trifloxystrobin, whereas a representative wild-type isolate did not germinate at concentrations higher than 0.1 μg/ml. In 2009, 172 isolates were collected from a total of 21 vineyards (juice and wine grapes): three vineyards with no fungicide application history (baseline sites), six research vineyards, and 12 commercial vineyards. QoI resistance was defined as the effective concentration that inhibited 50% of conidial germination (EC50) > 1 μg/ml. Isolates from baseline sites had EC50 values mostly below 0.01 μg/ml, while isolates that were highly resistant to trifloxystrobin (EC50 > 100 μg/ml) occurred in five research and three commercial wine grape vineyards at frequencies of 40 to 100% and 25 to 75% of the isolates, respectively. The G143A mutation was detected in every isolate with an EC50 > 1 μg/ml. These results suggest that fungicide resistance may play a role in suboptimal control of powdery mildew observed in some Michigan vineyards and emphasizes the need for continued fungicide resistance management.

Fitness Penalties in the Evolution of Fungicide Resistance

2018 ◽  
Vol 56 (1) ◽  
pp. 339-360 ◽  
Author(s):  
N.J. Hawkins ◽  
B.A. Fraaije
Keyword(s):  
Fungicide Resistance ◽  
Management Strategies ◽  
Crop Protection ◽  
Resistance Management ◽  
Nutrient Status ◽  
Selective Advantage ◽  
Life Cycle Stage ◽  
Epistatic Interactions ◽  
Resistance Risk ◽  
Evolution Of Resistance

The evolution of resistance poses an ongoing threat to crop protection. Fungicide resistance provides a selective advantage under fungicide selection, but resistance-conferring mutations may also result in fitness penalties, resulting in an evolutionary trade-off. These penalties may result from the functional constraints of an evolving target site or from the resource allocation costs of overexpression or active transport. The extent to which such fitness penalties are present has important implications for resistance management strategies, determining whether resistance persists or declines between treatments, and for resistance risk assessments for new modes of action. Experimental results have proven variable, depending on factors such as temperature, nutrient status, osmotic or oxidative stress, and pathogen life-cycle stage. Functional genetics tools allow pathogen genetic background to be controlled, but this in turn raises the question of epistatic interactions. Combining fitness penalties under various conditions into a field-realistic scenario poses an important future challenge.

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