Grapevine disease management update

The rainy, overcast weather has been perfect for the development of downy and powdery mildew and Botrytis. These diseases thrive under the high humidity we've been having and the overcast conditions have also prolonged the susceptibility of the leaves - they feel thinner and more pliant than when we have a lot of sun. It may have been necessary to stretch spray intervals due to wet vineyards. This is why it is so critical to use systemic products during this period - they don't wash off and most have post-infection activity so that if intervals are stretched, they'll have some kick-back. Remember that these products also tend to be more prone to resistance so it's critical to rotate among chemical families.

The rain helps to keep caps inside the clusters and promotes the germination of Botrytis spores and infection of berries. As berries swell and clusters tighten with all the rain, it is critical to get excellent coverage of the clusters, both inside and out.

The following table, extracted from Publication 360 and Cornell, gives information regarding the physical activity (protectant/postinfection/anti-sporulant/eradicant), movement in the vine (surface/locally systemic/systemic), risk of resistance (Low, Medium, High) and the fungicide groups to which the different fungicides belong.

The diseases against which the fungicides have activity are given in ( ). PM = powdery mildew, DM = downy mildew, BR = black rot, Bot = Botrytis bunch rot.

Fungicide Physical Mode of Action:

Protectant - active when present before the pathogen infects

Post-infection - active after infection has occurred but before symptoms develop

Anti-sporulant - reduces spore production so decreases spread of the disease

Eradicant - kills most of the fungal colony when applied after symptoms develop

Some products are classified as having more than one mode of action. Products like Inspire, Pristine, Luna Tranquility, Elevate, etc., are locally systemic so they penetrate into leaves and fruit but they prevent new infections from progressing beyond the very start and most of these products also have post-infection activity. For resistance management, they are not recommended for use after sporulation is present.

+ Fungicide has confirmed physical mode of action

+? Mode of action is speculated but no data to support

+/- Limited effectiveness for the physical mode of action. For example, phosphorous acid will have a very short period of protection (3 days tops).

Movement in the plant:

Surface = remains on the surface, is subject to wash off by rain or irrigation

Locally systemic = moves into the sprayed tissues but does not move to unsprayed tissues

Systemic = moves from sprayed tissues to unsprayed tissues, usually fruit or new leaves

Resistance risk

Low - may be used back-to-back multiple times during the season

Medium - at some risk; rotation among families is recommended

High - resistance may develop quickly; always rotate among families and use no more than twice per season for downy and powdery mildew and preferably only once per season for Botrytis

Group
Fungicide
Protectant
Post Infection
Anti-Sporulant
Eradicant
Movement
in vine
Resistance
Risk
M
Coppers
+ (DM)
+/- (PM)
Surface
L
M
Sulphurs
+ (PM)
+ (PM)
+/- (PM)
+ (PM)
Surface
L
M
Ferbam
+ (DM, BR)
Surface
L
M
Polyram
+ (DM, BR)
Surface
L
M
Manzate Pro-stick
+ (DM, BR)
L
M
captans
+ (DM)
Surface
L
M
Folpan
+ (DM)
Surface
L
2
Rovral
+ (Bot)
+ (Bot)
+ (Bot)
Locally systemic
H
3
Inspire
+ (PM, BR)
+ (PM, BR)
+ (PM, BR)
Locally systemic
H
3
Nova 40 W
+ (PM, BR)
+ (PM, BR)
+ (PM, BR)
Locally systemic
H
3
Mettle
+ (PM, BR)
+ (PM, BR)
+ (PM, BR)
Locally systemic
H
4
Ridomil Gold MZ
+ (DM)
+ (DM)
+ (DM)
Systemic
H
7
Cantus/Lance
+? (PM)
+ (PM)
+ (PM)?
Locally systemic
M
7+9
Luna Tranquility
+ (PM, Bot)
+ (PM, Bot)
+ (PM, Bot)
Locally systemic
M
9
Scala
+ (Bot)
+ (Bot)
+ (Bot)
Locally systemic
H
9
Vangard
+ (Bot)
+ (Bot)
+ (Bot)
Locally systemic
H
9+12
Switch
+ (Bot)
+ (Bot)
+ (Bot)
Locally systemic
M
11
Flint
+ (PM, BR)
+ (PM)
+ (PM)
Locally systemic
H
11
Sovran
+ (PM, BR)
+/- (DM)
+ (PM)
+ (PM)
Locally systemic
H
11&7
Pristine WG
+ (PM, BR, DM)
+ (PM)
+ (PM)
Locally systemic
M
17
Elevate
+ (Bot)
+ (Bot)
+ (Bot)
Locally systemic
M
22
Gavel
+ (DM)
Surface
L
33
Phostrol/Rampart
+/- (DM)
+ (DM)
+ (DM)
+ (DM)
Systemic
M
40
Revus
+? (DM)
+ (DM)
+ (DM)
Locally systemic
M
40
Acrobat
+? (DM)
+ (DM)
+ (DM)
Systemic
H
40+45
Zampro
+ (DM)
+ (DM)
+ (DM)
Systemic
M
43
Presidio
+? (DM)
+? (DM)
+ (DM)
Locally systemic
M
44
Serenade ASO
+ (Bot, PM)
Surface
L
NC
MilStop
+ (PM)
+ (PM, Bot)
+ (PM)
Surface
L
U8
Vivando SC
+ (PM)
+ (PM)
+ (PM)
Locally systemic
M
U
Purespray Green Spray Oil
+ (PM)
+ (PM)
+ (PM)
Surface
L
P5
Regalia Maxx
+ (PM, Bot)
Systemic?
L

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