LERGREC | Plant Pathology | Fungicide Efficacy Trials 2002 You are here

Evaluation of fungicides for control of downy mildew (Plasmopara viticola) and Phomopsis cane and leaf spot (Phomopsis viticola) of grapes, 2002.

B. Hed and J. W. Travis
Lake Erie Regional Grape Research and Extension Center, North East, PA 16428
Penn State Fruit Research and Extension Center 290 University Drive, Biglerville PA 17307-1330

This trial was conducted with twelve-year-old Vitis interspecific hybrid 'Chancellor' at the Lake Erie Regional Grape Research and Extension Center, North East, PA. 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, and 100 gal/A. Rainfall for Apr, May, Jun, Jul, Aug, and Sep was 7.42, 8.13, 2.33, 2.61, 3.16, and 6.58 in., respectively. Phomopsis incidence and severity were determined on 6-7 Aug from the first five basal internodes and first 2 cluster rachises of 10 primary shoots per plot. Downy mildew disease incidence and severity were determined on 12-13 Sep from 25 clusters per plot

Results

Phomopsis disease pressure was most severe during May. Fungicide applications on 27 Apr (1) and 11 May (2) were critical for disease control, and only programs that included these applications, regardless of material, provided significant control of internode and rachis infections. Although Penncozeb (applied at 1-3) appeared to provide better control than BAS 516 (at 1-3) at the rates used, the differences were not statistically significant. Downy mildew first appeared on 10 Jun. Downy mildew disease pressure was moderate in early Jun, but decreased in late Jun and early Jul due to dry conditions and limited overnight dew periods. All programs provided equally significant control of cluster infections.

Phomopsis
Downy Mildew
   
Internodes
Rachises
  
Clusters
Treatment and rate/A
Timingz
 % Infected
% Area Infectedy
% Infected
% Infected
% Area
Infectedy
BAS 516 UD F 0.658 lb/A
1-7
29.0 ax
1.2 a
8.8 a
0.0 a
0.0 a
spacer
BAS 516 UD F 0.658 lb/A
1-7
31.5 a
1.8 a
8.8 a
0.0 a
0.0 a
spacer
Penncozeb 75 DF 3 lb/A
1, 2
Penncozeb 75 DF 4 lb/A
3
BAS 516 UD F 0.395 lb/A
4, 5, 7
Ziram 76 DF 4 lb/A
6
15.0 a
0.6 a
0.0 a
1.0 a
0.0 a
spacer
Penncozeb 75 DF 4 lb/A
3
Penncozeb 75 DF 4 lb/A + Sovran 50WG 4oz/A
4, 5
Ziram 76 DF 4 lb/A
6
Sovran 50WG 4oz/A
7
82.5 b
9.8 b
57.5 b
1.0 a
0.4 a
spacer
Penncozeb 75 DF 4 lb/A
3
Penncozeb 75 DF 3lb/A + Flint 50 WGD 2oz/A
4, 5
Ziram 76 DF 4 lb/A
6
Flint 50 WGD 2oz/A
7
85.0 b
9.9 b
55.0 b
3.0 a
0.7 a
spacer
Penncozeb 75 DF 4 lb/A + Serenade WP 6 lb/A
3
Penncozeb 75 DF 4 lb/A
4
Penncozeb 75 DF 3lb/A + Sovran 50WG 4oz/A
5
Serenade WP 6 lb/A
6, 7
86.5 b
15.3 b
68.8 b
1.0 a
0.2 a
spacer
Untreated Check
82.0 b
14.5 b
61.3 b
23.0 b
8.1 b

z Application timings: 1 = 27 April (3 days after bud burst); 2 = 11 May (1-2 in. shoot); 3 = 24 May (3-4 in. shoot); 4 = 7 Jun (pre-bloom); 5 = 19 Jun (post-bloom); 6 = 3 Jul; 7 = 15 Jul.
y Severity was rated using the Barratt-Horsfall scale and was converted to % area infected using Elanco conversion tables.
x Means followed by the same letters within columns are not significantly different according to Tukey-Kramer (P < 0.05).