Abstract
Powdery mildew is an economically-important pathogen of grapes worldwide. This report details the findings of our annual powdery mildew fungicide trials on grapevine cultivar Chardonnay (Vitis vinifera). The trials were conducted at Herzog Ranch, near Courtland, California in 2009. Treatments were placed in five adjacent trials in the vineyard. Spraying commenced in mid April, shortly after a heavy rainfall event that likely promoted the release of powdery mildew (Uncinula necator) ascospores from overwintering chasmothecia. Spraying was completed in mid July and treatments were evaluated for disease incidence and severity on 21 July 2009, at about the beginning of veraison. Trial I consisted of IR-4-funded biofungicide research that focused on two products: caprylic acid (a novel control agent in current development) and Actinovate (a registered product containing the bacterium Streptomyces lydicus WYEC106). Trials II-V included various fungicide products (either currently registered or in various stages of product development) including strobilurins, demethylase inhibitors, oils, and other materials. Spray frequencies varied from weekly applications to 21 day intervals. Temperatures were mild during much of the 2009 growing season, providing optimal conditions for the asexual reproduction and dispersal of powdery mildew. Risk index data was high from about mid-May through the rest of the evaluation period and the pathogen quickly colonized leaves. Disease pressure was higher than in similar trials conducted in 2007 or 2008. By mid-June, heavy to severe mildew was evident on untreated clusters. Treatment performances varied widely. Biological fungicides generally reduced disease severity, but were more effective when used in a combination program with synthetic materials. As a stand-alone product, caprylic acid was most effective when applied weekly at a concentration of 0.3% (v/v). At a concentration of 0.5% it consistently showed phytotoxic effects on berries. A few organic materials performed well, lowering disease severity to <10%: paraffinic oil + Foliar Supreme (sulfur + nutrient cocktail) and two types of fertilizers alternated with trifloxystrobin. Among synthetic products, difenoconzaole + cyprodinil, flutriafol, fluopyram, fluopyram + tebuconazole, quinoxyfen + alcohol ethoxylate (an adjuvant), various GWN4617 treatments, picoxystrobin, penthiopyrad, boscalid + pyraclostrobin alternated with triflumizole, and metrafenone gave good to excellent control of disease severity on fruit. These trials easily separate highly effective materials from those which give only moderate control of powdery mildew, however long-term assessment of treatment efficacy is best evaluated with experiments conducted at multiple locations, across several growing seasons, and on multiple grape cultivars.
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Claims 9
Claim · model-written summary
Disease pressure exceeded that in 2007 and 2008 trials.
- Taxon
- grapevine cultivar Chardonnay (Vitis vinifera)
Vitis viniferat0 - Interactor
- Uncinula necator
Erysiphe necatore1pathogen - Outcome
- Disease pressuree0
- Direction
- highere0
- Comparator
- similar trials conducted in 2007 or 2008e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Disease pressure was higher than in similar trials conducted in 2007 or 2008.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
e1“powdery mildew (Uncinula necator)”
Claim · model-written summary
Untreated clusters had heavy to severe mildew by mid-June.
VitisOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“By mid-June, heavy to severe mildew was evident on untreated clusters.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
Claim · model-written summary
Biological fungicides generally reduced disease severity.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Biological fungicides generally reduced disease severity, but were more effective when used in a combination program with synthetic materials.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
Claim · model-written summary
Biological fungicides were more effective in combination with synthetic materials.
- Treatment
- combination program with synthetic materialse0
- Outcome
- disease severitye0
- Direction
- more effectivee0
- Comparator
- Biological fungicidese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Biological fungicides generally reduced disease severity, but were more effective when used in a combination program with synthetic materials.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
Claim · model-written summary
Weekly 0.3% caprylic acid was the most effective stand-alone application.
- Treatment
- caprylic acide0
- Outcome
- most effectivee0
- Direction
- most effectivee0
- Value
- 0.3% (v/v)e0
- Qualifier
- applied weeklye0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“As a stand-alone product, caprylic acid was most effective when applied weekly at a concentration of 0.3% (v/v).”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
Claim · model-written summary
Caprylic acid at 0.5% consistently caused berry phytotoxicity.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“At a concentration of 0.5% it consistently showed phytotoxic effects on berries.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
e1“caprylic acid was most effective when applied weekly at a concentration of 0.3% (v/v)”
Claim · model-written summary
Paraffinic oil plus Foliar Supreme lowered disease severity below 10%.
- Treatment
- paraffinic oil + Foliar Supreme (sulfur + nutrient cocktail)e0
- Outcome
- disease severitye0
- Direction
- loweringe0
- Value
- <10%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lowering disease severity to <10%: paraffinic oil + Foliar Supreme (sulfur + nutrient cocktail) and two types of fertilizers alternated with trifloxystrobin.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
Claim · model-written summary
Fertilizers alternated with trifloxystrobin lowered disease severity below 10%.
- Treatment
- two types of fertilizers alternated with trifloxystrobine0
- Outcome
- disease severitye0
- Direction
- loweringe0
- Value
- <10%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“lowering disease severity to <10%: paraffinic oil + Foliar Supreme (sulfur + nutrient cocktail) and two types of fertilizers alternated with trifloxystrobin.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
Claim · model-written summary
Listed synthetic fungicides gave good to excellent fruit disease control.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Among synthetic products, difenoconzaole + cyprodinil, flutriafol, fluopyram, fluopyram + tebuconazole, quinoxyfen + alcohol ethoxylate (an adjuvant), various GWN4617 treatments, picoxystrobin, penthiopyrad, boscalid + pyraclostrobin alternated with triflumizole, and metrafenone gave good to excellent control of disease severity on fruit.”
t0“grapevine cultivar Chardonnay (Vitis vinifera)”
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