Forecasting and Management of Hop Downy Mildew

Gent, David H.; Ocamb, Cynthia M.; Farnsworth, Joanna

doi:10.1094/pdis-94-4-0425

Cited by 28 publications

(24 citation statements)

References 24 publications

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“…Simpler explanations would be direct effects such as avoidance of disease-favorable weather (9,23) or inoculum reduction. Indirect effects could include reduced susceptibility of foliage, cones, or both following thorough pmning or altered plant growth characteristics with different pmning intensities which, in tum, could affect canopy development and microclimate favorability to both diseases.…”

Section: Discussionmentioning

confidence: 99%

“…Other studies have noted that the amount and titning of primary inoculum appearance exert a great influence on powdery mildew and downy mildew outbreaks on hop (9,15,17,27), as well as polycyclic diseases in other systems (1,14). Epidemiological theory predicts that management of polycyclic diseases can be achieved by reducing initial disease intensity or the rate of disease increase (37).…”

Section: Discussionmentioning

confidence: 99%

“…The climate in western Oregon is characterized by cool, wet springs which can be favorable to downy mildew in some years (9). The climate in western Oregon is characterized by cool, wet springs which can be favorable to downy mildew in some years (9).…”

Section: Discussionmentioning

confidence: 99%

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Association of Spring Pruning Practices with Severity of Powdery Mildew and Downy Mildew on Hop

et al. 2012

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spring pruning practices with severity of powdery mildew and downy mildew on hop. Plant Dis. 96:1343-1351.Downy mildew (caused by Pseudoperonospora liumuli) and powdery mildew (caused by Podosphaera macularis) are important diseases of hop in the Pacific Northwest United States, and cultural practices may affect the severity of both diseases. The association of spring pruning quality and timing with severity of downy mildew and powdery mildew was assessed through analysis of survey data collected from commercial hop yards in Oregon and Washington. Among 149 hop yards surveyed, the most common pruning method was chemical desiccation (48% of yards), mechanical pruning (23%), or a combination of these practices (15%). The quality of pruning was assessed using a threecategory ordinal scale ("excellent", "moderate", or "poor") based on the amount of foliage remaining on plants following pruning. Excellent pruning quality was attained more often in yards pruned twice (74.6 to 82.1 % of yards) versus once (33.8% of yards), independent of pruning method. Seasonal severity of downy mildew in Oregon increased approximately twofold with reduction in pruning quality from excellent to moderate to poor. Pruning quality was not significantly related to levels of powdery mildew on leaves or cones in Oregon. Under more severe disease pressure in Washington, however, seasonal severity of powdery mildew on leaves and the incidence of cones with powdery mildew were significantly greater in yards that had poor pruning compared with excellent pruning. Moreover, yards that had excellent pruning quality received, on average, 1.1 to 1.5 fewer fungicide applications per season for downy mildew or powdery mildew compared with yards that had moderate or poor pruning quahty. This savings was associated with delayed initiation of the first application by 7.5 to 14.2 days in yards with excellent pruning quality. Replicated experiments in commercial yards in Oregon quantified the effect of delaying pruning timing 5 to 21 days compared with growers' standard practices on the diseases and yield. Downy mildew suppression by delayed pruning was dependent on cultivar and year of sampling, being significantly reduced fivefold only in 'Willamette' in 2007. Severity of powdery mildew and cone yield was similar between plots that received the delayed or standard pruning timing treatments. Collectively, these studies emphasize that early spring sanitation measures are associated with reduced primary inoculum and are critically important for managing both downy mildew and powdery mildew. A savings of at least one fungicide application per year appears achievable when spring pruning is conducted thoroughly and slightly delayed compared with growers' current practices.Cultural disease management practices are actions that involve the manipulation of the plant, its components, crop refuse, and the environment to reduce or prevent disease (5,26,31,34). In hop (Humulus lupulus L.), cultural practices are an important component of integrated management of the t...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Association of Spring Pruning Practices with Severity of Powdery Mildew and Downy Mildew on Hop

et al. 2012

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“…Disease outbreaks can be polyetic, as individual plants can become chronically infected and consistently produce basal spikes. This leads to greater numbers and earlier emergence of diseased shoots in subsequent seasons (Salmon and Ware 1925;Johnson and Anliker 1985;Neve 1991;Gent et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Susceptibility of Hop Cultivars to Downy Mildew: Associations with Chemical Characteristics and Region of Origin

Woods

Gent

2016

Plant Health Progress

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Hop downy mildew (caused by Pseudoperonospora humuli) is a yield-limiting disease in many hop-production regions of the world. In this research, 110 cultivars that are or were widely grown in the United States, Europe, or Australasia were evaluated in western Oregon over three years for their reaction to the shoot infection phase of downy mildew and vigor. There was a large range of downy mildew susceptibility and vigor amongst commercial cultivars, with some cultivars possessing a very high level of resistance. Overall, however, disease resistance and vigor were significantly greater in cultivars originating from Europe than those originating from the United States, Japan, and Australia/New Zealand. Amongst a subset of 79 cultivars, vigor was negatively correlated with levels, in cones, of cohumulone, a chemical constitute of bittering acids typically found in germplasm derived from North America. The generally poor vigor observed in cultivars derived outside of Europe likely is indicative of a lack of tolerance to the crown infection phase of the disease. Thus, the best sources of downy mildew resistance seems to be found in cultivars from the United Kingdom and continental Europe, and such cultivars are typically lower yielding and lack distinctive aroma and flavor characteristics presently desired by craft brewers. Introgression of downy mildew resistance into North American germplasm with high yield and desirable brewing characteristics is needed. Accepted for publication 3 March 2016. Published 7 March 2016.

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“…Hu et al [20], point out that Propamocarb and Fosetyl have good curative and protective effects against oomycetes, as found in P. capsici, that's being back up in the current investigation. In synthetic fungicides with the best disease management efficiency were (RIDOMIL GOLD ® (Metalaxyl + Chlorothalonil) + PREVICUR ® ENERGY (Propamocarb + Fosetyl)), Matheron & Porchas [21] proved that Fosetyl suppress sporangium formation, motility, zoospores and clamidospores germination; and has a very high efficacy activity, just like with Metalaxyl [22]. It also reduces Phytophthora spp destructive ability.…”

Section: Plant Heightmentioning

confidence: 99%

Control Alternatives for Damping-Off in Tomato Seedling Production

Michel-Aceves¹,

D韆z-N醞era²,

Ariza-Flores³

et al. 2019

Phyton

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In two tomato genotypes, we assessed control alternatives for dampingoff with combinations of chemical fungicides and native/commercial strains of biological agents. Forty treatments consisting of 19 levels of mixing products, chemical fungicides, native strains and commercial products from biological control agents, and untreated treatment were used onto Ramsés and Toro hybrids. They were distributed on an incomplete block design in divided plots arrangement, where genotypes constitute the larger ones and the 8-repetition mixed products, the smaller ones. Putting 180 mL of fungal complexes, made of spores and mycellium Fusarium-solani (2 × 106 UFC), Rhizoctonia-solani (1 × 106 UFC), Phytophthoracapsici (1 × 105 UFC) and Sclerotium-rolfsii (mycellium-sclerotia) on each seedling trays, made inoculation possible. The mixtures of (Bacillus spp. + Streptomyces spp. + Trichoderma spp.) + (Propamocarb + Fosetyl); (Bacillus spp. + Streptomyces spp. + Trichoderma spp.) + (Metalaxyl + Chlorothalonil); Pseudomonas fluorescens + Streptomyces + Micromonospore + Sporideamium + Aminoacidos, Péptidos, Carbohidratos) + (Propamocarb + Fosetyl); the native strain of Trichoderma asperellum + (Propamocarb + fosetil) and the native strains Trichoderma asperellum + Bacillus subtilis, diminished damping-off, prevented its appearance and had most significant agronomic characteristics. In contrast to this, combination of (Mancozeb) + (Free iodine) + (Metalaxyl + Chlorothalonil) + (Methyl thiophanate) produced some toxicity in the plant. In addition, Ramsés presented the best agronomic parameters, while Toro had the utmost fresh and dry weight in root.

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Forecasting and Management of Hop Downy Mildew

Cited by 28 publications

References 24 publications

Association of Spring Pruning Practices with Severity of Powdery Mildew and Downy Mildew on Hop

Association of Spring Pruning Practices with Severity of Powdery Mildew and Downy Mildew on Hop

Susceptibility of Hop Cultivars to Downy Mildew: Associations with Chemical Characteristics and Region of Origin

Control Alternatives for Damping-Off in Tomato Seedling Production

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