Evaluation of Fungicides for the Control of <i>Peronospora belbahrii</i> on Sweet Basil in New Jersey

Homa, Kathryn; Barney, William P.; Ward, Daniel L.; Wyenandt, Christian A.; Simon, James E.

doi:10.1094/pdis-02-14-0200-re

Cited by 34 publications

(18 citation statements)

References 16 publications

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“…Other studies have tested some of these fungicides (McGrath, 2016a(McGrath, , 2016bMcGrath and Sexton, 2017;Raid et al, 2017), including glasshouse studies that demonstrated that fungicides mefenoxam + copper hydroxide, mandipropanid, and azoxystrobin also reduced disease (Gilardi et al, 2013). Field studies by Homa et al (2014) also showed that mandipropamid, cyazofamid, and phosphorous acid were consistently effective, whereas azoxystrobin and fluopicolide were only effective in one of two trials.…”

Section: Discussionmentioning

confidence: 99%

“…Therefore, it may be possible to develop elite sweet basil cultivars with genetic resistance to basil downy mildew in the near future. Registered commercial fungicides, including organic production control measures (e.g., hydrogen dioxide with peroxyacetic acid, copper salts, Streptomyces lydicus) and nonorganic measures (e.g., monopotassium and dipotassium salts of phosphorus acid, potassium phosphite, and azoxystrobin) have been used with varying levels of success managing downy mildew (Gilardi et al, 2013;Homa et al, 2014;Patel et al, 2016;Pintore et al, 2016). Unregistered but effective compounds include fluopicolide, mefenoxam + copper hydroxide, and oxathiapiprolin + chlorothalonil .…”

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confidence: 99%

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Evaluation of Selected Fungicide Application Regimes and Biotic Agents for the Management of Basil Downy Mildew

Zhang

Babadoost

Young

et al. 2018

hortte

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Basil downy mildew (Peronospora belbahrii) is a destructive disease that occurs in sweet basil (Ocimum basilicum). Foliar fungicide treatments could reduce infection and the severity of foliar symptoms over the course of the growing season. Multiple fungicides in variable combinations, application rates, and sequences were applied to basil foliage weekly over the course of a field season in Illinois (14 July to 8 Sept. 2014), and the treatment effects on basil downy mildew were evaluated three times. The evaluated treatments included mixtures and different rotations of azoxystrobin, potassium phosphite, mandipropamid, cyazofamid, oxathiapiprolin, experimental compound A18269SE, dimethomorph, zoxamide + mancozeb, fluazinam, fluopicolide, mefenoxam + copper hydroxide, fenamidone, mancozeb, and ametoctradin + dimethomorph. Potassium phosphite, which is known to be effective against other downy mildew pathogens, was included in combination with other fungicides or in fungicide application sequences. Disease severity was rated in fungicide-treated plots (0% to 20%) and compared with the control (73% to 80%) at each evaluation time. All fungicide treatments significantly reduced the area under the disease progress curve values compared with the untreated control. Adding a nonionic surfactant did not improve the efficacy of any of the chemical treatments evaluated for reducing downy mildew. Organic basil growers need novel, effective products to minimize damage from basil downy mildew. To aid organic basil growers, two novel, effective biocontrol agents were evaluated, Bacillus amyloliquefaciens AS 43.3 and Papiliotrema flavescens OH 182.9 3C (formerly Cryptococcus flavescens). Greenhouse experiments were conducted with the fungicides quinoxyfen and azoxystrobin serving as negative and positive fungicide treatment controls, respectively. Azoxystrobin reduced downy mildew according to the greenhouse tests, but neither quinoxyfen nor the biocontrol agents reduced downy mildew severity compared with the untreated control. This study identified 13 fungicide regimens that resulted in less than 10% basil downy mildew disease severity. More studies are needed to identify effective control products for basil downy mildew on organic basil.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Evaluation of Selected Fungicide Application Regimes and Biotic Agents for the Management of Basil Downy Mildew

Zhang

Babadoost

Young

et al. 2018

hortte

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“…By considering the epidemiology of the seed transmitted P. belbahrii and its repercussions on control measures (Garibaldi et al 2004b;2007;Thines et al 2009), different approaches of disease management need to be evaluate. Since from the discovery of downy mildew of basil, the seriousness of the attacks and loss of production have been stimulated numerous studies in different basil production areas in the world (Gullino et al 2009;McGranth et al 2010;Mersha et al 2012;Homa et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the use of chemicals in the field is complicated by the scalar type of harvest, which makes very difficult to comply with the intervals required between the last treatment and harvest. In fact, being the causal agent of the disease very aggressive, field sprays, even when carried out with the most effective products, provide a only partial control under severe disease pressure (Gilardi et al 2013;Homa et al 2014) and are not considered the wisest control methods, because of the risk of selection of strains of the pathogen resistant to the fungicides having a specific mode of action.…”

Section: Introductionmentioning

confidence: 99%

Seed dressing to control downy mildew of basil

et al. 2015

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Four experimental trials were carried out in order to evaluate the efficacy of different products (chemicals, resistance inducers and natural products) as well as heat air when applied to basil seeds naturally infested by Peronospora belbahrii, the causal agent of downy mildew of basil, a pathogen which is seed transmitted. Seed quality, as vigour index, was also evaluated. In general, seed treatment had a positive effect on the reduction of disease incidence and on plant biomass at the end of each trial, with very satisfactory results when disease incidence was lower than 10% and still satisfactory results with a higher disease incidence. Although many of the fungicides, resistance inducers and thyme oil treatments tested showed a significant disease reduction compared with the untreated control, the protection offered was only partial. Moreover, the effectiveness of the tested seed treatments varied considerably between the trials. The seeds treatment with heat air (65°C for 10 min) significantly reduced the number of infected plants per container. The interaction effect between the fungicides (at the lowest dosage tested, with the exception of acibenzolar-S-methyl, and dimethomorph), thyme oil and the heat air treatment was also significant. In terms of biomass, most treatments not significantly improved the fresh weight in comparison with the untreated control. The highest biomass was observed in the plots where seeds were dressed with mancozeb combined with heat air. Interestingly, thiram is also effective against other pathogens affecting basil and the thermal treatment and potassium phosphite are fully compatible with the rules of organic farming. Seed dressing represents the starting point of a full integrated approach for downy mildew management.

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“…Although there are a few fungicides currently registered for controlling BDM, significant crop loss and expenses can still occur with weekly preventative fungicide applications (Homa et al, 2014). Without effective fungicide control, BDM can cause 100% crop loss (Garibaldi et al, 2007;Wyenandt et al, 2010).…”

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confidence: 99%

Morphological Characteristics and Susceptibility of Basil Species and Cultivars to Peronospora belbahrii

Homa

Barney²,

Ward

et al. 2016

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Sweet basil (Ocimum basilicum) is the most economically important culinary herb in the United States. In 2007, a new disease, basil downy mildew (BDM), caused by the oomycete pathogen Peronospora belbahrii, was introduced into the United States and has since caused significant losses in commercial basil production. Although no commercial sweet basils available are resistant to P. belbahrii, other species of Ocimum have exhibited potential tolerance, resistance, or both. The objectives of this work were to determine if leaf morphological characteristics including stomata density and leaf curvature correlated with infection of plants by P. belbahrii, and thus could be used as selected characters in plant breeding. In 2011, 20 Ocimum cultivars including sweet (O. basilicum), cinnamon (O. basilicum), clove (O. basilicum), citrus (Ocimum ×africanum syn. Ocimum citriodorum), spice (Ocimum americanum syn. Ocimum canum), and holy basils (Ocimum tenuiflorum syn. Ocimum sanctum) were evaluated for susceptibility to downy mildew. Sweet basils were determined to be the most susceptible; cinnamon, clove, and Thai types were moderately susceptible; and citrus, spice, and holy types were least susceptible to downy mildew. Using those same 20 Ocimum species and cultivars, stomata length and density and leaf curvature were measured and correlated with downy mildew incidence and severity. In general, basil species with higher stomatal densities had higher downy mildew incidence and severity. High stomatal densities were mainly found in the sweet, cinnamon, and clove basils. Citrus and spice species with longer stomatal lengths generally exhibited lower downy mildew incidence. Holy basil, the least susceptible of all Ocimum sp. to P. belbahrii evaluated in this study, had the greatest stomatal density and shortest stomatal length. Some sweet basil cultivars with the highest downy mildew incidence also had the greatest downward leaf curvature, whereas other sweet basil cultivars with moderate downy mildew incidence had leaves that were nearly flat or curved upward. Holy, citrus, and spice basils with low downy mildew incidence had leaves that were nearly flat or curved upward. This study suggests that leaf curvature and stomatal density and length affect downy mildew development and sporulation. Considerations of these leaf morphological characteristics may be useful phenotypic traits in breeding for downy mildew resistance in Ocimum.

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Evaluation of Fungicides for the Control of Peronospora belbahrii on Sweet Basil in New Jersey

Abstract: 10

Cited by 34 publications

References 16 publications

Evaluation of Selected Fungicide Application Regimes and Biotic Agents for the Management of Basil Downy Mildew

Evaluation of Selected Fungicide Application Regimes and Biotic Agents for the Management of Basil Downy Mildew

Seed dressing to control downy mildew of basil

Morphological Characteristics and Susceptibility of Basil Species and Cultivars to Peronospora belbahrii

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