scholarly journals Resistance to Triadimefon and Benomyl: Dynamics and Impact on Managing Cucurbit Powdery Mildew

Plant Disease ◽  
2001 ◽  
Vol 85 (2) ◽  
pp. 147-154 ◽  
Author(s):  
Margaret Tuttle McGrath ◽  
Nina Shishkoff
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Podosphaera Xanthii ◽  
Pathogen Population ◽  
Action Threshold ◽  
Leaf Surfaces ◽  
Dmi Fungicides ◽  
Resistant Strains ◽  
Control Loss ◽  
Cucurbit Powdery Mildew

Frequency of fungicide-resistant strains of Podosphaera xanthii on pumpkins in New York before treatment varied from 3 to 80% for the demethylation inhibiting (DMI) fungicide triadimefon and from 0 to 48% for the benzimidazole fungicide benomyl between 1993 and 1996. When the initial frequency of triadimefon-resistant strains was less than 55%, one application of triadimefon plus chlorothalonil was effective. This application was made after reaching the action threshold of one leaf with powdery mildew symptoms per 50 old leaves (defined as the oldest third of the foliage). The frequency of triadimefon-resistant strains increased from 3 to 71% by 20 days after the first fungicide application in 1993. Triadimefon in the second application did not contribute to control. Loss of efficacy was due to resistance because, compared with triadimefon-treated pumpkins, pumpkins treated with other systemic fungicides were less severely infected by powdery mildew on abaxial leaf surfaces where the companion multi-site contact fungicide contributes little to control. Triadimefon was not effective in 1995 when 80% of the pathogen population was resistant before treatment. Benomyl was effective in 1995, but not in 1996 when 48% of the isolates tested were resistant to both benomyl and triadimefon before treatment. An in-field seedling assay was developed to determine local occurrence of resistant strains before the first treatment was needed. Although sensitivity of the pathogen population to the DMI fungicides myclobutanil and propiconazole also decreased after they were applied, these fungicides were more effective than triadimefon.

scholarly journals First Report of the Cucurbit Powdery Mildew Fungus (Podosphaera xanthii) Resistant to Strobilurin Fungicides in the United States

Plant Disease ◽  
2003 ◽  
Vol 87 (8) ◽  
pp. 1007-1007 ◽  
Author(s):  
M. T. McGrath ◽  
N. Shishkoff
Keyword(s):  
United States ◽  
New York ◽  
Powdery Mildew ◽  
The United States ◽  
Podosphaera Xanthii ◽  
Commercial Use ◽  
Strobilurin Fungicides ◽  
Research Fields ◽  
Cucurbit Powdery Mildew ◽  
Dmi Resistance

Resistance to strobilurin fungicides was documented in isolates collected from three fungicide efficacy experiments conducted in research fields in Georgia (GA), North Carolina (NC), and New York (NY). In these fields in 2002, strobilurins (fungicide group 11, quinone outside inhibitors [QoI]) when used alone on a 7-day schedule (use pattern not labeled) did not effectively control cucurbit powdery mildew. Strobilurin efficacy declined dramatically after the second application in New York (3). Efficacy also was reduced in commercial fields in Kentucky and research fields in Arizona, California, Kentucky, Illinois, Michigan, and Virginia in 2002 where strobilurins were used predominantly or exclusively. Isolates were collected on 22 July and 8 and 17 October after the last of four, five, and five applications of strobilurin (trifloxystrobin formulated as Flint or azoxystrobin formulated as Quadris) in experiments conducted by J. D. Moore in Chula, GA, M. McGrath in Riverhead, NY, and G. J. Holmes in Clayton, NC, respectively. A leaf-disk bioassay was used to determine fungicide sensitivity (2). Strobilurin sensitivity was determined using trifloxystrobin at 0, 0.5, 5, 50, and 100 μg/ml. Four of nine NY isolates, 19 of 21 GA isolates, and 13 of 15 NC isolates were resistant to strobilurins (grew well on disks treated with trifloxystrobin at 100 μg/ml). The geometric mean of the azoxystrobin baseline was 0.258 μg/ml for Podosphaera xanthii isolates collected in 1998 and 1999 in North America (4). Poor control with strobilurins under field conditions was associated with reduced sensitivity in vitro. Strobilurin sensitivity appeared to be qualitative as reported elsewhere (1). Two sensitive and three resistant isolates responded similarly when tested in another laboratory using kresoxim-methyl and pyraclostrobin (H. Ypema, personal communication). These findings and experiences elsewhere with QoI-resistant P. xanthii indicate that cross-resistance probably extends among multiple QoI's (1). Strobilurins have been available for commercial use in the United States since 1998, when azoxystrobin received Section 18 registration in some states. Federal registration was granted in March 1999. Strobilurin resistance was detected after 2 years of commercial use elsewhere in the world (1). All isolates tested in the current study were from research fields where selection pressure for resistance could have been higher than in commercial fields where strobilurins are used with demethylation inhibitors (DMIs; fungicide group 3) and contact fungicides in alternation or tank mixtures to prevent or delay resistance development. Resistance in commercial fields will reduce the utility of strobilurins, including those not yet registered, and eliminate an important tool for managing DMI resistance. Strobilurins and DMIs are the only systemic fungicides registered for cucurbit powdery mildew in the United States. Managing DMI resistance may be challenged by multiresistant strains. Strobilurin-resistant isolates also exhibited reduced sensitivity to DMIs, tolerating triadimefon at 50 to 100 μg/ml (2). One suggestion to improve resistance management is to apply a contact fungicide with strobilurins as well as DMIs. References: (1) H. Ishii et al. Phytopathology 91:1166, 2001. (2) M. T. McGrath et al. Plant Dis. 80:697, 1996. (3) M. T. McGrath and N. Shishkoff. Fungic. Nematic. Tests. (In press). (4) G. Olaya et al. Phytopathology (Abstr.) 90 (suppl):S57, 2000.

scholarly journals Transformation of the cucurbit powdery mildew pathogen Podosphaera xanthii by Agrobacterium tumefaciens

2016 ◽  
Vol 213 (4) ◽  
pp. 1961-1973 ◽  
Author(s):  
Jesús Martínez‐Cruz ◽  
Diego Romero ◽  
Antonio Vicente ◽  
Alejandro Pérez‐García
Keyword(s):  
Agrobacterium Tumefaciens ◽  
Powdery Mildew ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Pathogen ◽  
Cucurbit Powdery Mildew

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 Monitoring Methyl Benzimidazole Carbamate-Resistant Isolates of the Cucurbit Powdery Mildew Pathogen, Podosphaera xanthii, Using Loop-Mediated Isothermal Amplification

Plant Disease ◽  
2019 ◽  
Vol 103 (7) ◽  
pp. 1515-1524 ◽  
Author(s):  
Alejandra Vielba-Fernández ◽  
Antonio de Vicente ◽  
Alejandro Pérez-García ◽  
Dolores Fernández-Ortuño
Keyword(s):  
Amino Acid ◽  
Powdery Mildew ◽  
Amino Acid Change ◽  
Color Change ◽  
Isothermal Amplification ◽  
Podosphaera Xanthii ◽  
Lamp Product ◽  
Loop Mediated Isothermal Amplification ◽  
Cucurbit Powdery Mildew ◽  
Β Tubulin

Powdery mildew, caused by the fungus Podosphaera xanthii, is one of the most economically important diseases affecting cucurbit crops in Spain. Currently, chemical control offers the most efficient management of the disease; however, P. xanthii isolates resistant to multiple classes of site-specific fungicides have been reported in the Spanish cucurbit powdery mildew population. In previous studies, resistance to the fungicides known as methyl benzimidazole carbamates (MBCs) was found to be caused by the amino acid substitution E198A on β-tubulin. To detect MBC-resistant isolates in a faster, more efficient, and more specific way than the traditional methods used to date, a loop-mediated isothermal amplification (LAMP) system was developed. In this study, three sets of LAMP primers were designed. One set was designed for the detection of the wild-type allele and two sets were designed for the E198A amino acid change. Positive results were only obtained with both mutant sets; however, LAMP reaction conditions were only optimized with primer set 2, which was selected for optimal detection of the E198A amino acid change in P. xanthii-resistant isolates, along with the optimal temperature and duration parameters of 65°C for 75 min, respectively. The hydroxynaphthol blue (HNB) metal indicator was used for quick visualization of results through the color change from violet to sky blue when the amplification was positive. HNB was added before the amplification to avoid opening the lids, thus decreasing the probability of contamination. To confirm that the amplified product corresponded to the β-tubulin gene, the LAMP product was digested with the enzyme LweI and sequenced. Our results show that the LAMP technique is a specific and reproducible method that could be used for monitoring MBC resistance of P. xanthii directly in the field.

scholarly journals Ontogenic Resistance of Leaves and Fruit, and How Leaf Folding Influences the Distribution of Powdery Mildew on Strawberry Plants Colonized by Podosphaera aphanis

2014 ◽  
Vol 104 (9) ◽  
pp. 954-963 ◽  
Author(s):  
Belachew Asalf ◽  
David M. Gadoury ◽  
Anne Marte Tronsmo ◽  
Robert C. Seem ◽  
Andrew Dobson ◽  
...  
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Rapid Development ◽  
Differential Susceptibility ◽  
Rapid Acquisition ◽  
Age Related ◽  
Significant Difference ◽  
Leaf Surfaces ◽  
Ontogenic Resistance ◽  
Strawberry Cultivars

Ontogenic or age-related resistance has been noted in many pathosystems but is less often quantified or expressed in a manner that allows the concept to be applied in disease management programs. Preliminary studies indicated that leaves and fruit of three strawberry cultivars rapidly acquired ontogenic resistance to the powdery mildew pathogen, Podosphaera aphanis. In the present study, we quantify the development of ontogenic resistance in controlled inoculations of 10 strawberry cultivars using diverse isolates of P. aphanis in New York and Florida, USA, and in Norway. We report the differential and organ-specific development of ontogenic resistance in the receptacle and externally borne strawberry achenes. We further report that rapid development of ontogenic resistance prior to unfolding of emergent leaves, rather than differential susceptibility of adaxial versus abaxial leaf surfaces, may explain the commonly observed predominance of powdery mildew on the lower leaf surfaces. Susceptibility of leaves and fruit declined exponentially with age. Receptacle tissue of berries inoculated at four phenological stages from bloom to ripe fruit became nearly immune to infection approximately 10 to 15 days after bloom, as fruit transitioned from the early green to the late green or early white stage of berry development, although the achenes remained susceptible for a longer period. Leaves also acquired ontogenic resistance early in their development, and they were highly resistant shortly after unfolding and before the upper surface was fully exposed. No significant difference was found in the susceptibility of the adaxial versus abaxial surfaces. The rapid acquisition of ontogenic resistance by leaves and fruit revealed a narrow window of susceptibility to which management programs might be advantageously adapted.

scholarly journals Outbreak of Cucurbit Powdery Mildew on Watermelon Fruit Caused by Podosphaera xanthii in Southwest Florida

Plant Disease ◽  
2011 ◽  
Vol 95 (12) ◽  
pp. 1586-1586 ◽  
Author(s):  
C. S. Kousik ◽  
R. S. Donahoo ◽  
C. G. Webster ◽  
W. W. Turechek ◽  
S. T. Adkins ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Morphological Characteristics ◽  
The United States ◽  
Tween 20 ◽  
Conidial Suspension ◽  
Podosphaera Xanthii ◽  
Its Sequence Analysis ◽  
Fruit Samples ◽  
Cucurbit Powdery Mildew ◽  
Fruit Surface

Cucurbit powdery mildew caused by the obligate parasite Podosphaera xanthii occurs commonly on foliage, petioles, and stems of most cucurbit crops grown in the United States. (3). However, in the field, fruit infection on cucurbits including watermelon (Citrullus lanatus), is rarely, if ever, observed (2). Consequently, it was atypical when severe powdery mildew-like symptoms were observed on seedless and seeded watermelon fruit on several commercial farms in southwestern Florida during November and December 2010. Severe powdery mildew was also observed on ‘Tri-X 313’ and ‘Mickey Lee’ fruit grown at SWFREC, Immokalee, FL. Infected fruit developed poorly and were not marketable. Powdery mildew symptoms were mainly observed on young immature fruit, but not on mature older fruit. Abundant powdery mildew conidia occurred on fruit surface, but not on the leaves. Conidia were produced in chains and averaged 35 × 21 μm. Observation of conidia in 3% KOH indicated the presence of fibrosin bodies commonly found in the cucurbit powdery mildew genus Podosphaera (3). Orange-to-dark brown chasmothecia (formerly cleisthothecia) containing a single ascus were detected on the surface of some fruit samples. Conidial DNA was subjected to PCR using specific primers designed to amplify the internal transcribed spacer (ITS) region of Podosphaera (4). The resulting amplicons were sequenced and found to be 100% identical to the ITS sequences of P. xanthii in the NCBI database (D84387, EU367960, AY450961, AB040322, AB040315). Sequences from the watermelon fruit isolate were also identical to several P. fusca (synonym P. xanthii), P. phaseoli (GQ927253), and P. balsaminae (AB462803) sequences. On the basis of morphological characteristics and ITS sequence analysis, the pathogen infecting watermelon fruit can be considered as P. xanthii (1,3,4). The powdery mildew isolate from watermelon fruit was maintained on cotyledons of squash (Cucurbita pepo, ‘Early Prolific Straight Neck’). Cotyledons and leaves of five plants each of various cucurbits and beans were inoculated with 10 μl of a conidial suspension (105conidia/ml) in water (0.02% Tween 20). Two weeks after inoculation, abundant conidia were observed on cucumber (Cucumis sativus, ‘SMR-58’) and melon (Cucumis melo) powdery mildew race differentials ‘Iran H’ and ‘Vedrantais’. However, no growth was observed on melon differentials ‘PI 414723’, ‘Edisto 47’, ‘PMR 5’, ‘PMR 45’, ‘MR 1’, and ‘WMR 29’ (2,3). The powdery mildew isolate from watermelon fruit behaved as melon race 1 (3). Mycelium and conidia were also observed on fruit surface of watermelon ‘Sugar Baby’ and a susceptible U.S. plant introduction (PI 538888) 3 weeks after inoculation. However, the disease was not as severe as what was observed in the fields in fall 2010. The pathogen did not grow on plants of Impatiens balsamina or on select bean (Phaseolus vulgaris) cultivars (‘Red Kidney’, ‘Kentucky Blue’, and ‘Derby Bush’), but did grow and produce abundant conidia on ‘Pinto bush bean’. Powdery mildew on watermelon fruit in production fields can be considered as a potentially new and serious threat requiring further studies to develop management strategies. References: (1) U. Braun and S. Takamatsu. Schlechtendalia 4:1, 2000. (2) A. R. Davis et al. J. Am. Soc. Hortic. Sci. 132:790, 2007. (3) M. T. McGrath and C. E. Thomas. In: Compendium of Cucurbit Diseases. American Phytopathological Society, St. Paul, MN, 1996. (4) S. Takamatsu and Y. Kano. Mycoscience 42:135, 2001.

Genetic diversity analysis of the cucurbit powdery mildew fungus Podosphaera xanthii suggests a clonal population structure

2015 ◽  
Vol 119 (9) ◽  
pp. 791-801 ◽  
Author(s):  
Alessandro Pirondi ◽  
David Vela-Corcía ◽  
Luca Dondini ◽  
Agostino Brunelli ◽  
Alejandro Pérez-García ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Population Structure ◽  
Powdery Mildew ◽  
Diversity Analysis ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
Clonal Population ◽  
Genetic Diversity Analysis ◽  
Clonal Population Structure ◽  
Cucurbit Powdery Mildew

Optimizing Use of DMI Fungicides for Management of Apple Powdery Mildew Caused by Podosphaera leucotricha in New York State

Plant Disease ◽  
2021 ◽  
Author(s):  
David Strickland ◽  
Sara M. Villani ◽  
Kerik Cox
Keyword(s):  
New York ◽  
Powdery Mildew ◽  
Disease Control ◽  
Disease Incidence ◽  
New York State ◽  
Optimal Timing ◽  
Fresh Market ◽  
Podosphaera Leucotricha ◽  
York State ◽  
Dmi Fungicides

Powdery mildew, caused by the ascomycete Podosphaera leucotricha, is an endemic disease found wherever apples are grown that negatively impacts both tree vigor and fresh market yield. In the absence of durable host resistance, chemical management is the primary means of disease control. Demethylation inhibitor (DMI) fungicides are widely used to manage apple powdery mildew, but members within this fungicide class have been observed to differ in efficacy with respect to disease control. Moreover, debate exists as to the optimal timing of DMI fungicide applications for management of apple powdery mildew. In this regard, the goal of this study was to determine the best-use practices for DMI fungicides to manage apple powdery mildew in New York State. Multi-year trials were conducted to evaluate the potential differential efficacy performance of four common DMI fungicides, as well as additional trials to assess optimal application timing. In all years, we observed that treatments of flutriafol and myclobutanil consistently had the lowest incidences of powdery mildew compared to difenoconazole and fenbuconazole. In the 2018 and 2021 trials, the newly registered mefentrifluconazole was more comparable to the difenoconazole program with respect to powdery mildew disease incidence. We hypothesize that differences in DMI efficacy may be due to each fungicides’ water solubility and lipophilicity characteristics, and thus their ability to move systemically in the host or more easily penetrate the surface of germinating conidia. Applications timed between petal fall and first cover resulted in the lowest incidence of powdery mildew on terminal leaves of apple shoots compared to applications timed prior to petal fall. These observations are contrary to previous studies conducted in regions with differing climates. We also found that the incidence of secondary powdery mildew observed two weeks after petal fall was influenced by applications of DMI fungicides during the previous season. For example, management programs consisting of applications of flutriafol or myclobutanil in the prior season tended to have lower incidence of apple powdery in the following spring, presumably owing to reductions in overwintering inoculum. Despite reports of DMI resistance in other apple pathosystems, the DMI fungicide class is still relevant for the successful management of apple powdery mildew in New York State.

Sensitivities of Cucurbit Powdery Mildew Fungus (Podosphaera xanthii) to Fungicides

2020 ◽  
Vol 21 (4) ◽  
pp. 272-277
Author(s):  
Mohammad Babadoost ◽  
Salisu Sulley ◽  
Yiwen Xiang
Keyword(s):  
United States ◽  
Powdery Mildew ◽  
Succinate Dehydrogenase ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
Midwestern United States ◽  
Quinone Outside Inhibitors ◽  
Cucurbit Powdery Mildew ◽  
Succinate Dehydrogenase Inhibitors

This study was conducted to evaluate the sensitivity of cucurbit powdery mildew fungus (Podosphaera xanthii) to major fungicides used for managing this pathogen in the Midwestern United States. Fungicides azoxystrobin from the quinone outside inhibitors group, cyflufenamid from the phenylacetamide group, penthiopyrad from the succinate dehydrogenase inhibitors group, quinoxyfen from the quinolines group, and triflumizole from the demethylation inhibitors group were tested for their effectiveness for preventing infection of cucurbits by P. xanthii. In 2015 and 2016, 37 isolates of P. xanthii were evaluated for their sensitivity to azoxystrobin (Quadris 2.08SC), cyflufenamid (Torino 0.85SC), penthiopyrad (Fontelis 1.67SC), and triflumizole (Procure 480SC) on cucumber ‘Bush Crop’ cotyledon leaves. The number of isolates sensitive to tested concentrations of Quadris 2.08SC, Torino 0.85SC, Fontelis 1.67SC, and Procure 480SC was 8 (22%), 21 (57%), 20 (54%), and 23 (62%), respectively. During 2015 to 2018, Quadris 2.08SC, Torino 0.85SC, Fontelis 1.67SC, quinoxyfen (Quintec 250SC), and Procure 480SC were tested for their effectiveness for managing powdery mildew on pumpkin ‘Howden’ in the field. The results showed that powdery mildew was effectively managed in the plots treated with Procure 480SC and Quintec 250SC. However, management of the disease was less successful in the plots treated with Quadris 2.08SC, Torino 0.85SC, and Fontelis 1.67SC.

scholarly journals Genome Resource of Podosphaera xanthii, the Host-specific Fungal Pathogen that Causes Cucurbit Powdery Mildew

2020 ◽  
Author(s):  
Seunghwan Kim ◽  
Sathiyamoorthy Subramaniyam ◽  
Myunghee Jung ◽  
Eun-A Oh ◽  
Tae Ho Kim ◽  
...  
Keyword(s):  
Powdery Mildew ◽  
Fungal Pathogen ◽  
Fungal Pathogens ◽  
Fruits And Vegetables ◽  
Draft Genome ◽  
Pathogen Resistance ◽  
Effector Proteins ◽  
Podosphaera Xanthii ◽  
Valuable Resource ◽  
Cucurbit Powdery Mildew

Approximately 33 types of commonly consumed fruits and vegetables are members of the Cucurbitaceae, making it an important crop family worldwide. However, pathogen resistance to pesticides/fungicides has become a growing problem in cultivation practices. The identification of the effector proteins in each unique fungus–host pair would help toward the development of strategies for preventing the infection of important crops. In this study, we characterized the genome of Podosphaera xanthii, the fungal pathogen that causes powdery mildew disease in Cucurbitaceous plants. A first-draft genome of 209.08 MB was assembled and compared with those of 25 other fungal pathogens, particularly for identifying candidate secreted effector proteins. This draft genome can serve as a valuable resource for future genomic/proteomic studies of P. xanthii and its host-specific pathogenesis.

Sign in / Sign up

Export Citation Format

Share Document