scholarly journals Fungicide Programs Affect ‘Practical’ Resistance Development in Cucurbit Powdery Mildew of Pumpkin

HortScience ◽  
2008 ◽  
Vol 43 (6) ◽  
pp. 1838-1845 ◽  
Author(s):  
Christian A. Wyenandt ◽  
Nancy Maxwell ◽  
Daniel L. Ward
Keyword(s):  
High Risk ◽  
Powdery Mildew ◽  
Fungicide Resistance ◽  
Low Risk ◽  
Resistance Development ◽  
Progress Curve ◽  
Action Committee ◽  
Bottom Side ◽  
Orange Fruit ◽  
Cucurbit Powdery Mildew

The effects of two pumpkin cultivars and five fungicide programs on cucurbit powdery mildew development and yield were evaluated in southern New Jersey from 2005 to 2007. Each year, five separate fungicide programs were applied to powdery mildew-tolerant cv. Magic Lantern or powdery mildew-susceptible cv. Howden pumpkin. The five fungicide programs applied season-long (10 applications per program) included: 1) protectant fungicides only: manzate + sulfur [Fungicide Resistance Action Committee (FRAC) codes M3 + M2] alternated weekly with maneb + copper hydroxide (FRAC codes M3 + M1); 2) standard program: chlorothalonil + myclobutanil (FRAC codes M5 + 3) alternated with azoxystrobin (FRAC code 11); 3) intensive program: maneb + myclobutanil (FRAC codes M3 + 3) alternated with [famoxadone + cymoxanil] (FRAC codes 11 + 27); 4) FRAC code 3 weekly: chlorothalonil + myclobutanil (FRAC codes M5 + 3) alternated with myclobutanil (FRAC code 3); and 5) FRAC code 11 weekly: chlorothalonil + azoxystrobin (FRAC codes M5 + 11) alternated with azoxystrobin (FRAC code 11). In each year, there were no significant interactions between the fungicide program and cultivar. In each year, area under disease progress curve values were highest when a FRAC code 11 fungicide was applied weekly compared with a FRAC code 11 fungicide applied in a weekly rotation with a FRAC code 3 fungicide or a FRAC code 3 fungicide applied weekly. Visual examination of leaves at the end of each production season revealed there were no significant differences in powdery mildew development on the top (adaxial) or bottom (abaxial) sides of leaves in untreated subplots. Powdery mildew development was lower on the bottom sides of leaves when a Fungicide Resistance Action Committee (FRAC) code 3 fungicide was applied weekly compared with a FRAC code 11 fungicide applied weekly or when a FRAC code 3 fungicide was rotated weekly with a FRAC code 11 fungicide in each year of the study. There were no significant differences in total number of harvested fruit, number of harvested orange fruit, average weight of orange fruit, or percentage of harvested orange fruit between fungicide programs in each year of the study. Results of this study, based on arcsine-transformed area under disease progress curve (AUDPC) values and top and bottom leaf surface ratings, suggest that the weekly use of the FRAC code 11 fungicide lead to the development of practical resistance in the field population of cucurbit powdery mildew. Rotating a FRAC code 11 and FRAC code 3 fungicide weekly resulted in lower AUDPC values and powdery mildew development on the bottom side of leaves in 2 of 3 years of this study. However, based on AUPDC values and leaf rating values, the level of control obtained with the high-risk FRAC code 3 fungicide was less during each consecutive year. The immediate erosion of control (i.e., qualitative resistance) as observed with the FRAC code 11 fungicide or the gradual decline of control (quantitative resistance) as observed with the FRAC code 3 fungicide over three growing seasons shows the importance of being able to detect and understand the mechanisms of practical resistance development. This understanding will allow appropriate fungicide control recommendations to be made in a timely (i.e., real-time) manner. Importantly, fungicide resistance is most likely to develop on the bottom side (abaxial) of pumpkin leaves when effective, low-risk (nonmobile) fungicides (FRAC code M numbers) are tank-mixed with high-risk fungicides in cucurbit powdery mildew control programs. Tank-mixing fungicides that have a high risk for resistance development with protectant fungicides that have a low risk for resistance development remains critically important when controlling cucurbit powdery mildew and reducing the potential for fungicide resistance development. This is the first report of cucurbit powdery mildew developing practical resistance to a FRAC code 11 and FRAC code 3 fungicide in New Jersey.

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

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.

Determining “Practical” Fungicide Resistance Development and Drift in the Control of Cucurbit Powdery Mildew in Pumpkin

2010 ◽  
Vol 11 (1) ◽  
pp. 4 ◽  
Author(s):  
Christian A. Wyenandt ◽  
Nancy L. Maxwell
Keyword(s):  
Powdery Mildew ◽  
Active Ingredient ◽  
Fungicide Resistance ◽  
Cross Resistance ◽  
Resistance Development ◽  
Leaf Surfaces ◽  
Cucurbit Powdery Mildew

In 2006 and 2007, nine fungicides were evaluated to determine if “practical” fungicide resistance could be identified and if fungicide resistance drift occurred in cucurbit powdery mildew of pumpkin. The fungicides and/or tank mixes whose active ingredient(s) were evaluated included: sulfur (FRAC code M1), chlorothalonil (M5), myclobutanil (3), pyraclostrobin (11), azoxystrobin (11), quinoxyfen (13), chlorothalonil + myclobutanil (M5 + 3), famoxadone + cymoxanil (11 + 27), pyraclostrobin + boscalid (11 + 7), and water only (control). Based on visual ratings of upper and lower leaf surfaces, a FRAC code 11 resistance cucurbit powdery mildew population was present in both years. Practical resistance and cross resistance were identified where a FRAC code 11 fungicide had not been applied season-long as well as where a FRAC code 11 fungicide was applied weekly or in rotation with another fungicide chemistry. Resistance to a FRAC code 3 fungicide was not identified where a FRAC code 3 fungicide had been applied season-long, or in rotation, or where no FRAC code 3 fungicide was applied. This study demonstrates that cucurbit powdery mildew populations resistant and/or cross resistant to FRAC code 11 fungicides can develop and have the potential to disseminate into and be detected in areas where no FRAC code 11 fungicides have been applied. Accepted for publication 11 October 2010. Published 22 November 2010.

scholarly journals Using Epidemiological Principles to Explain Fungicide Resistance Management Tactics: Why do Mixtures Outperform Alternations?

2018 ◽  
Vol 108 (7) ◽  
pp. 803-817 ◽  
Author(s):  
James A. D. Elderfield ◽  
Francisco J. Lopez-Ruiz ◽  
Frank van den Bosch ◽  
Nik J. Cunniffe
Keyword(s):  
High Risk ◽  
Disease Control ◽  
Fungicide Resistance ◽  
Total Yield ◽  
Resistance Management ◽  
Careful Consideration ◽  
Low Risk ◽  
Model Parameterization ◽  
Grapevine Powdery Mildew ◽  
Label Dose

Whether fungicide resistance management is optimized by spraying chemicals with different modes of action as a mixture (i.e., simultaneously) or in alternation (i.e., sequentially) has been studied by experimenters and modelers for decades. However, results have been inconclusive. We use previously parameterized and validated mathematical models of wheat Septoria leaf blotch and grapevine powdery mildew to test which tactic provides better resistance management, using the total yield before resistance causes disease control to become economically ineffective (“lifetime yield”) to measure effectiveness. We focus on tactics involving the combination of a low-risk and a high-risk fungicide, and the case in which resistance to the high-risk chemical is complete (i.e., in which there is no partial resistance). Lifetime yield is then optimized by spraying as much low-risk fungicide as is permitted, combined with slightly more high-risk fungicide than needed for acceptable initial disease control, applying these fungicides as a mixture. That mixture rather than alternation gives better performance is invariant to model parameterization and structure, as well as the pathosystem in question. However, if comparison focuses on other metrics, e.g., lifetime yield at full label dose, either mixture or alternation can be optimal. Our work shows how epidemiological principles can explain the evolution of fungicide resistance, and also highlights a theoretical framework to address the question of whether mixture or alternation provides better resistance management. It also demonstrates that precisely how spray tactics are compared must be given careful consideration.[Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

scholarly journals Evaluation of a Warning System for Early-Season Control of Grapevine Powdery Mildew

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 104-110 ◽  
Author(s):  
Tito Caffi ◽  
Sara E. Legler ◽  
Vittorio Rossi ◽  
Riccardo Bugiani
Keyword(s):  
High Risk ◽  
Powdery Mildew ◽  
Risk Model ◽  
Warning System ◽  
Northern Italy ◽  
Low Risk ◽  
Short Message ◽  
Early Season ◽  
Weather Forecasts ◽  
Model Driven

In several grape-growing areas of the world, including northern Italy, powdery mildew epidemics, caused by Erysiphe necator, are mainly triggered by the ascospores produced in overwintered chasmothecia. Growers in northern Italy usually control the disease with fixed-interval fungicide applications. A warning system was developed for early-season powdery mildew control based on (i) short-term weather forecasts, (ii) a model that simulates the severity of each E. necator ascosporic infection, and (iii) a mobile phone short-message system. This warning system was evaluated in six vineyards in northern Italy from 2006 to 2008, between bud break of vines and early berry development; an unsprayed control was compared with “low-risk” and “high-risk” model-driven sprays and a calendar-based “grower” spray program. Use of the warning system reduced disease severity on leaves and bunches compared with the unsprayed control and resulted in the same level of control of powdery mildew as the grower's spray program, with reduced fungicide applications and costs. On average, 5.7 sprays were applied following the grower's spray program (with an average cost of 221 €/ha/year); use of the warning system reduced fungicide applications by 36% (low-risk program, saving of 56 €/ha/year) or 75% (high-risk program, saving of 161 €/ha/year).

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 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.

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