Evaluation of the efficacy of first fungicide application on the
control of Erysiphe necator and the ascospores release on Douro Region
Carmo Val1, Fernando Alves 1, Diana Monteiro 3, António Silvestre2 & Isabel Cortez2
1ADVID
2CITAB,
– Associação para o Desenvolvimento da Viticultura no Douro, Quinta de Santa Maria, Apt. 137, 5050-106 Godim, Portugal [email protected],[email protected]
Universidade de Trás-os-Montes e Alto Douro, Departamento de Agronomia, Apartado 1013, 5001-801 Vila Real, Portugal [email protected],
– Escola Profissional de Desenvolvimento Rural do Rodo, Quinta do Rodo, 5050-092 Godim, Portugal
3EPDRR
Methodology
Introduction
The powdery mildew (Erysiphe necator) is the most important disease which manifests itself more
aggressively, in the vineyard in the Douro Region (RDD), Portugal. In RDD, the hibernation occurs
mainly in the form of cleistothecia the "drapeaux" are rarely seen, and it is assumed that the first
infections were caused by ascospores (Freitas et al, 2005). The cleistothecia are attached on the
surface of organs, show a spherical (ostiole lacking), which is initially white in color and evolve to
reach the yellow and dark brown to maturation (84-115 mM) (Fig. 1). Each Cleistoteca contains
between 4 to 6 asci (50-60 x 25-40 mM) and each contains 4-8 ascospores unicellular, hyaline and
ovoid (10-14 x 15-25 mm) (Dubos, 1999). (Fig. 2).
The main objective of this work was to evaluate different treatment strategies in early vegetative
cycle occurs where the release of ascospores.
The plot where the study was conducted is located in
Quinta de S. Luíz (Cima Corgo, Douro Demarcated
Region). The vineyards of this plot are installed in 2
rows terraces, and the variety is Tinta Roriz
(Tempranilho), one of the most frequently planted in
this region.
At the beginning of March, we put small blades with
vaseline with the purpose to catch ascospora (Fig. 3).
The blades witches were changed after every time a
rainfall episode happens.
To evaluate the efficacy of the several chemical
strategies of controlling oidium, we define the following
protocol (Tab. 1)
Fig. 3 – Suporte de lâminas para captura de ascósporos
Table 1 - Schedule of treatments for each modality
Modalidalities
1T
2T
3T
4T
Fig. 1 – Cleistotecas mildew in various states of training
Schedule of treatments
28/04/2011
WP
-
14/04/2011
WP
WP
-
12/05/2011
WP
IBE
IBE
Phenology (Bagiollini)
F
G
H+
Dose/ha
4kg/ha
4kg/ha
4kg/ha; 35ml/hl
Fig. 2 – Cleistotecas observed under the microscope and its ascospores
Results
0,24
a
0
Jul-11
Mar-11
0,60
P
NC
ab
% Oídium
a
b
4,50
15
0,45
b
a
b
a
b
3,00
10
0,30
b
0,08
5
1,50
0,15
0,00
0
0,00
0,00
b
1T
2T
3T
4T
1T
2T
3T
4T
1T
2T
3T
4T
1T
2T
b
a
3T
4T
Fig 5 - Mean values of: - percentages of attack (Oidium%); - kg per vine (P); - number of clusters per vine (NC) and average weight of bunches (PMC) of the modalities
20-05-2011
08-06-2011
12-07-2011
Fig. 6 - Evolution of development of powdery mildew from fruit set until harvest
Bibliography
ALVES, F. & ALMEIDA, F. (2003) - Contributo para a discussão de estratégias de combate ao oídio da videira Uncinula necator (Schw.) Burr na Região Demarcada do Douro
DUBOS, B. (1999) - Les maladies cryptogamiques de la vigne. Champignons parasites des organes herbacés et du bois de la vigne. Editions Féret, Bordeaux. pp: 174.
FREITAS, J. & VAL, M. (2005) - Captura de ascósporos de oídio da videira na Região do Douro. Actas VII Encontro Nacional de Protecção Integrada. Instituto Politécnico de
Coimbra, Dezembro de 2005: 145-153.
T. (ºC)
10
0
Sep-11
20
10
Aug-11
30
20
2-Jun
23-May
5-May
12-May
28-Apr
40
Fig.4 - Dynamic of ascospores release per week and accumulated rainfall and evolution of the climate from March to September (temperature and precipitation)
a
0,16
11-Apr
0
31-Mar
0
25-Mar
5
2
50
TMed
30
Jun-11
10
R (mm)
40
May-11
4
P. (mm)
15
18-Mar
P. (mm)
6
50
Apr-11
8
6,00
ab
PMC
a
10
25
20
20
0,32
30
N.º ascospores / week
The ascospores release began at least on March 18th and occurred till June 2nd with
coincidence among the release picks and the episodes of rain, except on two dates (on
May 5th it rained and there was not a strong ascospores release and on May 23rd it did
not rain and there was a ascospores pick discharge) (Fig 4) .
The efficacy of the first spraying on the development of the disease and its effect was
evaluated by determination of the percentage of infected clusters, the yield (kg) per
vine (P), the number of clusters per vine (NC) and the average weight of bunches
(PMC) on the treatments.
During spring and summer of 2011, Oïdium disease had a high expression in Douro
region due to the high temperature and precipitation in April and May.
The severity of Oïdium was higher (statistically different P<0.05) on the treatment 1T
(without sprayings) in comparison with 2T, 3T and 4T (different active compounds and
different spraying periods). On 1T the number of clusters/vine, the yield/vine and the
weight of bunches/vine was lower in comparison with the other treatments (Fig 5).
Among 2T, 3T and 4T there was not significant differences for the parameters evaluated,
showing that it was only necessary to start the sprayings near blooming (4T) to control
the oidium development .
The early treatments don´t show a significantly increase in the control efficacy of the
disease, as also stated by Alves et al, 2003.
23-09-2011
23-09-2011