2008 Research Report to the Michigan Grape & Wine Industry Council

Transcription

1 2008 Research Report to the Michigan Grape & Wine Industry Council Proposal Title: Evaluating environmentally friendly treatments for management of sour rot and Botrytis bunch rot in wine grapes Principal Investigator: Name: Annemiek Schilder Mailing address: 104 CIPS Building, MSU, East Lansing, MI Telephone: Fax: Introduction; Priority Addressed: Sour rot of grapes is a wet rot that spreads rapidly throughout grape clusters. It is sometimes confused with Botrytis bunch rot but can be distinguished by its wet appearance and vinegar smell as well as frequent presence of fruit flies. It is caused by acetic acid bacteria (Acetobacter spp.) and various undesirable yeasts and fungi. Unlike Botrytis bunch rot, it usually lacks fungal sporulation. Botrytis bunch rot can also be very destructive. A gray mold is often present on and between the berries. Botrytis bunch rot is caused by the fungus Botrytis cinerea, which can also blight other plant parts such as leaves and inflorescences. Compact clusters, diffuse (late) powdery mildew infections, hail and insect damage can predispose grapes to both sour rot and Botrytis bunch rot infection. Aside from the use of fungicides, there are few options for control of Botrytis bunch rot and there are no chemical options for control of sour rot. Leaf pulling has been suggested as a method to control both types of rots (W.D. Gubler and J.C. Broome, 2007, Organic Grape Disease Management in California [book chapter]). In addition, several fungicides claim to provide control or suppression of sour rot, including Oxidate (hydrogen peroxide) (BioSafe Systems, Inc.) and the biocontrol products Serenade (Bacillus subtilis) (AgraQuest, Inc.) and BlightBan 506 (Pseudomonas fluorescens) (Nufarm Americas, Inc.). None of these products had been evaluated for control of sour rot in Michigan. The goal of this project is to evaluate environmentally sound practices for control of both sour rot and Botrytis bunch rot. Results will directly impact the ability of grape growers to control a disease that is unpredictable and difficult to manage. Original goals and objectives of the project: The objectives of this proposal were to: 1) Determine the efficacy of biological control agents and soft fungicides on sour rot and Botrytis bunch rot incidence 2) Evaluate the efficacy of leaf removal in the fruit zone on sour rot and Botrytis bunch rot incidence Project Period: October 1, 2007 to September 30,

2 Work accomplished during the period, including methods 1) Determine the efficacy of biological control agents and soft fungicides on sour rot and Botrytis bunch rot incidence The experiment was conducted in a mature commercial vineyard in Berrien Springs, MI. Vines were spaced at 7 x 9 ft and were cordon-trained on a 2-wire trellis and hand pruned. The following treatments were evaluated: Serenade (Bacillus subtilis) + NuFilm (a surfactant), Blightban (Pseudomonas fluorescens), TrigoCor (Bacillus subtilis an experimental biocontrol agent from Cornell University), Oxidate (hydrogen peroxide), Switch (cyprodinil + fludioxonil), Cuprofix (copper sulfate), Sevin XLR (carbaryl an insecticide), potassium metabisulfite, and a standard fungicide program (Pristine [pyraclostrobin + boscalid], Elite [tebuconazole] + Ziram [ziram], Elite + Phostrol [sodium, potassium and ammonium phosphites]). Treatments were applied to 4-vine plots and were replicated four times in a randomized complete block design. Sprays were applied with an R&D Research CO 2 cart-styled sprayer equipped with six bottles (0.8 gal each), a twin gauge Norgren pressure regulator set at 55 psi, and a single XR TeeJet 8002VS nozzle on a 5-ft spray boom. Spray dates and approximate phenological stages were as follows: 1 Jul (1 st post-bloom); 14 Jul (2 nd post-bloom, bunch closure); 28 Jul (3 rd post-bloom); 11 Aug (4 th post-bloom); 3 Sep (5 th post-bloom, veraison). An insecticide (Sevin XLR) was applied with a backpack sprayer by Steve VanTimmeren on 10 Sep. Additional fungicide and insecticide sprays were applied over the entire vineyard by the grower during the season. Spray volume was 40 gpa. Total rainfall between sprays was 2.19, 1.44, 1.0, 0.43 and 3.44 in., respectively. Disease was assessed on the center two vines of each plot on 25 Sep. Botrytis bunch rot and sour rot were similarly assessed on 25 clusters per plot. Sour bunch rot was identified as wet, rotting fruit with a vinegar smell. Botrytis bunch rot was identified as rotting fruit with gray sporulation. Phomopsis fruit rot was identified by brown shriveling fruit with or without black pycnidia and necrotic berry stems or rachises. In addition, since downy mildew was present on leaves, downy mildew incidence (% leaves exhibiting disease) and severity (% leaf area infected on diseased leaves only) were visually estimated on 25 randomly selected leaves per plot. Overall severity was calculated as (incidence x severity)/100. Vines were also monitored for signs of phytotoxicity. 2) Evaluate the efficacy of leaf removal in the fruit zone on sour rot and Botrytis bunch rot incidence The experiment was conducted in the same vineyard and trial as described above. Leaves were removed to open up the canopy around the clusters on 9 Jul (berry touch) and 8 Aug (preveraison), About two to three leaves were removed around clusters as needed to reduce shading and increase sunlight exposure. Disease was assessed on the center two vines of each plot on 25 Sep as described above. Summary of the expenditures during the period. Budget category Original Budget ($) Expenditures ($) _ Salary 6,000 8,754 Fringe 2, Travel Materials and supplies Other direct costs 0 0 Total 10,000 10,000 2

3 Results and conclusions of the project 1) Determine the efficacy of biological control agents and soft fungicides on sour rot and Botrytis bunch rot incidence Due to heavy precipitation in early September and tight cluster architecture of the grape cultivar Vignoles, Botrytis bunch rot and sour rot were prevalent at harvest time. Phomopsis fruit rot also was present. Sour rot severity was visibly higher in plots near the wooded edge of the vineyard. Fruit flies were common in sour rot-infected clusters and ants were common in Botrytis-infected clusters. No insects appeared to be associated with Phomopsis fruit rot. More than one disease could be present on a cluster, but Phomopsis-infected clusters often had less sour rot and Botrytis bunch rot, probably due to a reduction in cluster tightness as a result of berries shriveling and dropping from the clusters. All treatments significantly reduced overall severity of Botrytis bunch rot, although the standard fungicide program was numerically the most effective (Table 1). The standard program was based on a previous trial in In a way, it was surprising that Switch, which is generally considered a strong Botryticide, had only moderate efficacy. Perhaps the 11-oz rate (which is on the low side) needs to be increased. An application of Sevin XLR was statistically similar to the standard fungicide program, which was somewhat surprising as well. The efficacy of Sevin XLR against Botrytis bunch rot may be due to its effect on insects (e.g., ants) that play a role in disease development, either by transmitting spores or causing injuries that predispose berries to infection. Alternatively, Sevin XLR may have a direct effect on the fungus as well. The fact that a late spray of Sevin XLR (on 10 Sep) had so much effect, suggests the importance of late sprays for Botrytis bunch rot control. None of the treatments significantly reduced sour rot, emphasizing the difficulty in controlling this disease (Table 2). However, the lack of significance could also be partially explained by the uneven distribution of sour rot in the vineyard, as it was observed that sour rot was more severe near the wood s edge. However, all of the treatments showed a numerical reduction in sour rot, and of the fungicide applications, Blightban had the lowest amount of sour rot, followed by Serenade Max. In future, treatments may need to be applied on tighter intervals closer to harvest. With regards to Phomopsis fruit rot, the most effective treatments were Switch, Serenade Max + NuFilm, potassium metabisulfite, Oxidate, TrigoCor and Cuprofix (Table 3). The efficacy of a late spray of potassium metabisulfite and three late-season sprays of TrigoCor suggest that Phomopsis fruit infections can occur late in the season although many fruit infections develop from rachis or berry stem infections that occur much earlier. Blightban, Sevin XLR and the standard program did not significantly reduce Phomopsis fruit rot. When considering the combination of Botrytis fruit rot and sour rot, the most effective chemical treatment was the standard fungicide program followed by Sevin XLR and potassium metabisulfite. Interestingly, leaf removal at pre-veraison was numerically the best treatment (Table 4). For the combination of all rots (incl. Phomopsis), all fungicides provided significant and statistically equivalent disease control. The best chemical treatment (numerically) was potassium metabisulfite, followed by Switch, the standard fungicide program, and Serenade. In general, the trial suggests that late sprays (within 2 weeks of harvest) were probably the most important for control of Botrytis and sour rot, whereas earlier sprays were probably more important for control of Phomopsis fruit rot. Different products had different efficacy against components of the disease complex. What is interesting is that late-season sprays (including one spray of potassium metabisulfite at veraison) still provided a measure of control of Phomopsis fruit rot, which indicates that disease spread occurs even late in the season (probably from berry 3

4 to berry within the cluster). Downy mildew on the foliage appeared late in the season and its severity was quite low but differences among treatments were noted (Table 5). All treatments, except leaf removal at preveraison, significantly reduced overall severity of downy mildew. Serenade Max + NuFilm was numerically the most effective treatment. It is not clear why the insecticide Sevin XLR was effective against downy mildew, but it may be due to surfactant activity against the zoospores, which are very sensitive and swim in a film of water prior to infection. 2) Evaluate the efficacy of leaf removal in the fruit zone on sour rot and Botrytis bunch rot incidence Leaf removal on both dates reduced Botrytis bunch rot and both treatments were statistically similar to the standard fungicide program (Table 1), providing about 50-62% disease control. Leaf removal also numerically reduced sour rot, even though this difference was not statistically significant (Table 2). In both cases, leaf removal at pre-veraison appeared slightly more effective than leaf removal at berry touch. A possible explanation for this may be that after berry touch, new leaves could still develop and possibly shade the clusters anew. Leaf removal did not significantly reduce Phomopsis fruit rot (Table 3). When considering the combination of Botrytis bunch rot and sour rot, the most effective treatment overall was leaf removal at pre-veraison, with leaf removal at berry touch being statistically similar but numerically less effective (Table 4). For overall severity of all fruit rots combined (Botrytis bunch rot, sour rot, and Phomopsis rot), leaf removal at pre-veraison was not statistically different from leaf removal at berry touch: both treatments reduced disease compared to the untreated control (Table 4). Table 1 Botrytis bunch rot Application timing z Incidence Severity Overall severity x Untreated ab 34.9 a 24.3 a [%] w Serenade Max 3 lb + NuFilm pt... 3, 4, a 21.1 bcd 15.4 b [37] BlightBan A oz... 3, 4, abc 22.0 bcd 15.5 b [36] Cuprofix Ultra 3 lb... 3, 4, abc 22.4 bcd 14.4 bc [41] Oxidate 1% (v/v)... 3, 4, cd 26.8 b 13.9 bc [43] TrigoCor (undiluted)... 3, 4, abc 23.2 bc 13.8 bc [43] Switch 11 oz... 3, 4, abc 18.7 cd 12.5 bc [49] Potassium metabisulfite 4.4 lb abc 19.0 cd 12.2 bc [50] Leaf removal x... Berry touch 61.3 abc 20.3 bcd 12.1 bcd [50] Sevin XLR 2 qt bcd 20.2 bcd 10.7 bcd [56] Leaf removal x... Pre-veraison 60.0 abc 15.4 d 9.3 cd [62] Ziram 76DF 3 lb + Elite 45WP 6 oz Elite 45WP 4 oz + Phostrol 4 pt... 3, 4, d 18.0 cd 6.7 d [72] z Spray dates: 1 = 1 Jul (1 st post-bloom); 2 = 14 Jul (2 nd post-bloom, bunch closure); 3 = 28 Jul (3 rd post-bloom); 4 = 11 Aug (4 th post-bloom); 5 = 3 Sep (5 th post-bloom, veraison), 6 = 10 Sep. y Column means followed by the same letter are not significantly different according to Fisher s Protected LSD test (P<0.05). x Leaves were manually removed around each cluster to improve airflow and sunlight penetration on 9 Jul 2008 (berry touch) or 8 Aug (pre-veraison). w Bracketed values denote percent control relative to the untreated check. 4

5 Table 2 Sour rot Application Incidence Severity Overall severity timing z x Untreated ns 21.5 ns 14.8 ns TrigoCor (undiluted)... 3, 4, Switch 11 oz... 3, 4, Sevin XLR 2 qt Leaf removal x... Berry touch Potassium metabisulfite 4.4 lb Ziram 76DF 3 lb + Elite 45WP 6 oz Elite 45WP 4 oz + Phostrol 4 pt... 3, 4, Oxidate 1% (v/v)... 3, 4, Cuprofix Ultra 3 lb... 3, 4, Serenade Max 3 lb + NuFilm pt... 3, 4, BlightBan A oz... 3, 4, Leaf removal x... Pre-veraison z Spray dates: 1 = 1 Jul (1 st post-bloom); 2 = 14 Jul (2 nd post-bloom, bunch closure); 3 = 28 Jul (3 rd post-bloom); 4 = 11 Aug (4 th post-bloom); 5 = 3 Sep (5 th post-bloom, veraison), 6 = 10 Sep. y Column means followed by the same letter are not significantly different according to Fisher s Protected LSD test (P<0.05); ns = not significant. x Leaves were manually removed around each cluster to improve airflow and sunlight penetration on 9 Jul 2008 (berry touch) or 8 Aug (pre-veraison). w Bracketed values denote percent control relative to the untreated check. 5

6 Table 3 Phomopsis fruit rot Application timing z Incidence Severity Overall severity x [%] v Untreated a 22.1 ns 17.8 a Sevin XLR 2 qt a ab [26] BlightBan A oz... 3, 4, b abc [30] Leaf removal w... Berry touch 81.3 a abc [31] Leaf removal w... Pre-veraison 86.3 a abc [31] Ziram 76DF 3 lb + Elite 45WP 6 oz Elite 45WP 4 oz + Phostrol 4 pt... 3, 4, a abc [34] Cuprofix Ultra 3 lb... 3, 4, b bc [68] Oxidate 1% (v/v)... 3, 4, b bc [68] TrigoCor (undiluted)... 3, 4, b bc [72] Potassium metabisulfite 4.4 lb b c [73] Serenade Max 3 lb + NuFilm pt... 3, 4, b c [74] Switch 11 oz... 3, 4, b c [75] z Spray dates: 1 = 1 Jul (1 st post-bloom); 2 = 14 Jul (2 nd post-bloom, bunch closure); 3 = 28 Jul (3 rd post-bloom); 4 = 11 Aug (4 th post-bloom); 5 = 3 Sep (5 th post-bloom, veraison), 6 = 10 Sep. y Column means followed by the same letter are not significantly different according to Fisher s Protected LSD test x Data did not pass Barlett s test for homogeneity of variance even after transformation; assumptions of the ANOVA may have been violated. w Leaves were manually removed around each cluster to improve airflow and sunlight penetration on 9 Jul 2008 (early berry touch) or 8 Aug (pre-veraison). v Bracketed values denote percent control relative to the untreated check. 6

7 Table 4 Combined rots (overall severity) Application timing z Botrytis rot + Sour rot [%] w Bot + SR + Phom. [%] w Untreated a 56.8 a TrigoCor (undiluted)... 3, 4, b y [34] 30.9 b [46] Serenade Max 3 lb + NuFilm pt... 3, 4, bc [40] 28.1 b [50] Cuprofix Ultra 3 lb... 3, 4, bc [40] 29.3 b [48] Oxidate 1% (v/v)... 3, 4, bc [41] 28.7 b [49] Switch 11 oz... 3, 4, bc [41] 27.4 b [52] BlightBan A oz... 3, 4, bc [42] 35.3 b [38] Leaf removal berry touch x... Berry touch 21.9 bcd [44] 34.1 b [40] Potassium metabisulfite 4.4 lb bcd [45] 26.3 b [54] Sevin XLR 2 qt bcd [47] 33.8 b [40] Ziram 76DF 3 lb + Elite 45WP 6 oz Elite 45WP 4 oz + Phostrol 4 pt... 3, 4, cd [59] 27.9 b [51] Leaf removal x... Pre-veraison 14.6 d [63] 26.8 b [53] z Spray dates: 1 = 1 Jul (1 st post-bloom); 2 = 14 Jul (2 nd post-bloom, bunch closure); 3 = 28 Jul (3 rd post-bloom); 4 = 11 Aug (4 th post-bloom); 5 = 3 Sep (5 th post-bloom, veraison), 6 = 10 Sep. y Column means followed by the same letter are not significantly different according to Fisher s Protected LSD test (P<0.05). x Leaves were manually removed around each cluster to improve airflow and sunlight penetration on 9 Jul 2008 (early berry touch) or 8 Aug (pre-veraison). w Bracketed values denote percent control relative to the untreated check. 7

8 Downy mildew, interestingly, was less severe in the treatment where leaves were removed at berry touch compared to the untreated control (Table 5); this was not the case with leaf removal at pre-veraison. However, the leaf removal treatments were considered not statistically different from each other. The reason for the disease reduction may be inoculum removal and/or a reduction of humidity at an important time of the disease cycle. No sunscald was noted on clusters in the trial. Table 5 Downy mildew on the leaf blade Application timing z Incidence Severity Overall severity x Untreated a 6.0 x a 1.64 x a [%] v Leaf removal w... Pre-veraison 16.3 ab 4.3 ab 0.90 ab [45] Switch 11 oz... 3, 4, bcd 3.5 bcd 0.53 bc [68] Leaf removal w... Berry touch 13.8 abc 2.5 bcd 0.40 bc [76] TrigoCor (undiluted)... 3, 4, bcd 1.6 bcd 0.18 bc [89] BlightBan A oz... 3, 4, bcd 1.6 bcd 0.15 bc [91] Cuprofix Ultra 3 lb... 3, 4, d 2.5 bcd 0.13 bc [92] Potassium metabisulfite 4.4 lb cd 2.0 bcd 0.13 bc [92] Oxidate 1% (v/v)... 3, 4, bcd 1.5 cd 0.13 bc [92] Sevin XLR 2 qt bcd 1.0 cd 0.11 c [93] Ziram 76DF 3 lb + Elite 45WP 6 oz 3, 4, Elite 45WP 4 oz + Phostrol 4 pt bcd 0.9 cd 0.11 bc [93] Serenade Max 3 lb + NuFilm pt... 3, 4, cd 0.8 d 0.08 c [95] z Spray dates: 1 = 1 Jul (1 st post-bloom); 2 = 14 Jul (2 nd post-bloom, bunch closure); 3 = 28 Jul (3 rd post-bloom); 4 = 11 Aug (4 th post-bloom); 5 = 3 Sep (5 th post-bloom, veraison), 6 = 10 Sep. y Column means followed by the same letter are not significantly different according to Fisher s Protected LSD test (P<0.05). x Data did not pass Barlett s test for homogeneity of variance even after transformation; assumptions of the ANOVA may have been violated. w Leaves were manually removed around each cluster to improve airflow and sunlight penetration on 9 Jul 2008 (early berry touch) or 8 Aug (pre-veraison). v Bracketed values denote percent control relative to the untreated check. Overall conclusions This research has shown that control of the bunch rot complex can be improved by the use of post-bloom fungicides as well as leaf removal and even a late spray of an insecticide. It appears that late sprays (within 2-3 weeks of harvest) were probably the most critical for control of Botrytis bunch rot and sour rot. In general, Botrytis bunch rot was easier to control than sour rot, as results were not statistically significant for sour rot. For controlling combined Botrytis bunch rot/sour rot, the most effective treatment actually was leaf removal at pre-veraison. For the combination of all rots (including Phomopsis fruit rot), numerically the best treatment was a single spray of potassium metabisulfite at veraison, but other treatments were statistically similar. All treatments, except leaf removal at pre-veraison also reduced downy mildew on the foliage; however, disease pressure was very low. 8

9 In Year 2 of the study, we will repeat the evaluation of the best products and practices from Year 1 and will also test a combination of leaf removal and chemical application to see if control can be improved when best practices are integrated (leaf removal should improve fungicide spray penetration). In addition, we will modify the timing of chemical applications, evaluating and 3 sprays at weekly intervals after veraison. Communications Activities, Accomplishments, and Impacts: Portions of this research were presented in a talk by Paolo Sabbatini at a Nebraska Winery and Grape Growers Association Meeting in November, This research will also be presented at various upcoming grape meetings during the 2009 growing season, including Viticulture Day. The data have been used to adjust recommendations for disease management in grapes in E-154, the Michigan Fruit Management Guide. In addition, the report will be submitted for publication in Plant Disease Management Reports in A poster abstract will be submitted for the Annual Meeting of the American Phytopathological Society to be held in Portland, Oregon in July, Funding Partnerships: No funding partnerships were established for this project in However, for 2009, we will apply for matching funds from product manufacturers as well as Viticulture Consortium East. We will work with Drs. Paolo Sabbatini and Tom Zabadal on an integrated project for control of Botrytis bunch rot and sour rot. 9