LERGREC
| Plant Pathology | Fungicide Efficacy
Trials 2001
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Evaluation of Fungicides for Control of Downy Mildew, Powdery Mildew, and Phomopsis Cane and Leaf Spot of Vitis interspecific hybrid 'Chancellor' Grapes, 2001
J.
W. Travis and B. Hed
Penn State Fruit Research and Extension Center, 290 University Drive Biglerville
PA 17307-1330
Lake Erie Regional Grape Research and Extension Center, North East, PA
16428
This trial was conducted in an eleven-year-old vineyard at the Lake Erie Regional Grape Research and Extension Center, North East, PA, where vines were trained to a single curtain, (no tie) system. Treatments were applied to 4-vine plots in a randomized complete block design with 4 replications. Fungicides were applied with a Friend covered-boom plot sprayer at 200 psi, applying 100 gal/A. Applications for all treatments, except the VITIS advised program, were made on 4 May (bud burst), 15 May (3-4 in. shoot), 28 May (8-9 in. shoot), 8 Jun (pre-bloom), 21 Jun (post-bloom), 3 Jul, and 16 Jul. Sevin 4F was applied at 2.5 quarts/A on 12 Jun to control insects. Rainfall for May, Jun, Jul, Aug, and Sep was 5.88, 4.13, 4.46, 6.88, and 4.09 in., respectively. Bud burst occurred on 3 May and full bloom on 19 Jun. Powdery and downy mildew disease incidence on 23 Jul was determined from 50 randomly selected leaves and clusters per plot. Phomopsis incidence on 15 Aug was determined from the first five basal internodes and first 2 cluster rachises of 10 randomly selected primary shoots per plot. Incidence and severity of powdery and downy mildew were determined on 20 Aug and 18 Sep from 25 randomly selected leaves and clusters per plot.
Results
Powdery Mildew:
Powdery mildew disease pressure was high. All chemical treatment programs
were providing significant control of leaf and cluster infections by late
July, although the TM 41503 and BAS 516 programs were statistically superior
to programs relying on Nova and/or Sovran. By late August, the incidence
of powdery mildew had reached 100% on leaves and clusters in plots of
the untreated check and all the Nova and/or Sovran chemical treatment
programs, but was significantly lower in the TM 41503 and BAS 516 treatments.
By August 20, treatments were characterized as follows with respect to
powdery mildew: treatments containing BAS 516 or TM 41503 had little or
no berry infection and very limited cluster rachis and leaf infection;
treatments containing Sovran and/or Nova had limited but common berry
infection, often extensive to severe rachis infection, and limited but
occasionally severe leaf infection; untreated vines had severe rachis
and leaf infection and common and occasionally severe berry infection.
By the 18 Sep rating, incidence on leaves and clusters was at 100% for
all treatments. Leaf and rachis infection was severe in treatments containing
Nova and/or Sovran, and in unsprayed plots, but still significantly limited
in treatments containing TM 41503 or BAS 516. All chemical treatment programs
controlled the severity of berry infections. In general, the severity
of berry infections in plots receiving TM 41503 or BAS 516 was extremely
light and lower than in treatments containing Sovran and/or Nova. TM 41503
provided numerically better control of leaf and berry infection than BAS
516, but the differences were never significant. However, the higher rate
of BAS 516 did provide significantly better control of rachis infection
than TM 41503. The higher rate of BAS 516 provided better numerical, but
not statistical control of leaf, rachis, and berry infections than the
lower rate.
Downy Mildew: Disease pressure was considered light to moderate in June and early July. Disease incidence rose slowly in unsprayed check plots, remaining below 10% on clusters until mid July, when incidence increased to 36.5% before clusters became resistant to downy mildew. All chemical treatment programs provided excellent control of downy mildew on Chancellor clusters.
Phomopsis disease
pressure was considered moderate in May and light in June and early July.
Only programs with BAS 516 (either rate) and Penncozeb/Ziram amended with
TM 41503 had a significantly lower incidence of Phomopsis on shoot internodes
than the untreated check. All other Penncozeb/Ziram programs were statistically
similar to the BAS 516 and TM 41503 amended Penncozeb/Ziram programs,
but were not statistically better than the check. All chemical treatment
programs provided significant control of Phomopsis rachis infections.
There was no statistically significant rate effect on the level of control
of shoot internode or cluster rachis infections with respect to BAS 516.
No phytotoxicity was observed.
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Powdery
Mildew1
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Downy
Mildew1
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Phomopsis1
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Clusters
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| Leaves |
Berries
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Rachis
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Clusters
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%
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%
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%Area3
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%Area3,4
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%Area3
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%Area3
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Internodes
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Rachises
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| Treatment and rate/A |
Timing2
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Infected
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Infected
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Infected
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Infected
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Infected
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Infected
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| BAS 516 UD F 0.395 lb/A |
1-7
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46.73 a5 | 0.19 abc5 | 33.16 ab5 | 0.0 a5 | 12.0 a5 | 3.8 a5 | ||
 |
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| BAS 516 UD F 0.526 lb/A |
1-7
|
28.67 a | 0.12 ab | 16.90 a | 0.0 a | 10.0 a | 3.8 a | ||
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| Penncozeb 75 DF 4 lb/A |
1,
2
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| Penncozeb 75 DF 4 lb/A + TM 41503 125 SC 9 fl oz/A |
3,
4
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| TM 41503 125 SC 9 fl oz/A + Ziram 76 DF 4lb/A |
5-7
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24.95 a | 0.05 a | 44.05 b | 0.0 a | 8.0 a | 6.3 a | ||
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| Penncozeb 75 DF 4 lb/A |
1,
2
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| Penncozeb 75 DF 3 lb/A + Sovran 50WG 4oz/A |
3,
4
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| Sovran
50WG 4oz/A + Ziram 76 DF 3 lb/A |
5-7
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77.74 b | 2.69 d | 95.40 c | 0.0 a | 13.5 ab | 8.8 a | ||
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| Penncozeb 75 DF 4 lb/A |
1,
2
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| Penncozeb 75 DF 4 lb/A + Nova 40 W 4 oz/A |
3,
4
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| Nova
40 W 4 oz/A + Ziram 76 DF 4 lb/A |
5-7
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79.83 b | 2.15 d | 95.62 c | 0.02 a | 13.0 ab | 16.3 a | ||
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| Penncozeb 75 DF 4 lb/A |
1,
2
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| Penncozeb 75 DF 4 lb/A + Nova 40 W 4 oz/A |
3
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| Penncozeb 75 DF 3 lb/A + Sovran 50WG 4oz/A |
4
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| Nova 40 W 4 oz/A + Ziram 76 DF 4 lb/A |
5,
7
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| Sovran 50WG 4oz/A + Ziram 76 DF 3 lb/A |
6
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74.21 b | 1.80 bcd | 93.17 c | 0.0 a | 12.5 ab | 15.0 a | ||
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| Spray timing advised by VITIS expert system6 | |||||||||
| Penncozeb 75 DF 4 lb/A |
1
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| Penncozeb 75 DF 4 lb/A + Nova 40 W 4 oz/A |
2,
4, 6
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| Penncozeb 75 DF 3 lb/A + Sovran 50WG 4oz/A |
3,
5
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| Sovran 50WG 4oz/A + Ziram 76 DF 3 lb/A |
7
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72.97 b | 1.87 cd | 96.72 c | 0.09 a | 13.5 ab | 12.5 a | ||
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| Untreated check |
1-
5
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91.47 b | 16.09 e | 97.01 c | 7.51 b | 31.5 b | 45.0 b | ||
1 Data shown are from
18 Sep rating for Powdery and Downy Mildew and from 15 Aug rating for
Phomopsis.
2 Dates for spray timings: 1 = 4 May; 2 = 15 May; 3 = 28 May; 4 = 8 Jun;
5 = 21 Jun; 6 = 3 Jul; 7 = 16 Jul.
3 Severity was rated using the Barratt-Horsfall scale and was converted
to % area infected using Elanco conversion tables.
4 Actual data are shown. Data were transformed by arcsine square root
transformation before statistical analysis.
5 Means followed by the same letters within columns are not significantly
different according to Tukey-Kramer (P < 0.05).
6 Dates for VITIS spray timings: 1 = 10 May; 2 = 20 May; 3 = 30 May; 4
= 11 Jun; 5 = 25 Jun; 6 = 6 Jul; 7 = 20 Jul.
