Developing an Effective Fungicide Spray Program for Wine Grapes In Ohio
Michael A. Ellis
OARDC
The Ohio
State University
Wooster Ohio
44691
The following information is intended to be “food for thought” in relation to developing a fungicide spray program for wine grapes in Ohio. The spray schedule presents various fungicide options that can be considered by growers. It is important to note that the schedule is intended to provide simultaneous control of black rot, powdery mildew, downy mildew and Phomopsis cane on leaf spot. The schedule is also intended to provide fungicide resistance management, primarily against the powdery mildew fungus. Note that there are usually several fungicide options that can be selected. This schedule does not contain all of the fungicides currently registered for use on grapes. Remember, these are only “Suggested Guidelines” for use in developing a fungicide program. The final program that you develop will depend upon the disease complex in your vineyard as well as economic considerations.
SUGGESTED
GUIDELINES FOR DEVELOPING A FUNGICIDE SPRAY PROGRAM
FOR WINE
GRAPES IN OHIO
This program is intended to provide simultaneous control of Block Rot, Powdery Mildew, Downy Mildew and Phomopsis Cane and Leaf Spot, as well as Fungicide Resistance Management
|
Application Timing |
Material (and
rate/A) |
|
NOTE: Mancozeb alone for Phomopsis only. If Powdery Mildew is a concern this early in the growing season, use: |
|
|
|
Mancozeb (3 lb/A) |
|
3-5 inch shoot |
Mancozeb (3 lb/A) |
NOTE: If Powdery Mildew is a major concern, Rubigan, Elite or Nova are the fungicides of choice to combine with Mancozeb. Also, be aware that the efficacy of Sulfur for Powdery Mildew control declines below 65°F. If cool temperatures persist (below 65°F), Rubigan, Elite or Nova should be used instead of Sulfur for Powdery Mildew early in the growing season. On Sulfur sensitive varieties, use Rubigan, Elite or Nova. If Powdery Mildew is not a problem, Mancozeb alone can be used.
NOTE: Always check the price (cost per acre per application) of each fungicide. At the rates recommended, fungicides may vary considerably in cost.
|
10-12 inch shoot |
Same fungicides |
|
Immediate prebloom |
(Strobilurin Fungicide) |
NOTE: It is important to alternate different fungicide chemistry in the program in order to prevent the development of fungicide resistant strains of fungi, especially powdery mildew. Our intention here is to alternate the sterol-inhibiting fungicides (Rubigan, Elite or Nova) with the strobilurin fungicides (Abound or Sovran).
|
First postbloom
spray |
(Strobilurin Fungicide) |
|
Second postbloom
spray |
Mancozeb (4 lb/A)
|
NOTE: In order to prevent or delay the development of fungicide resistance, the sterol-inhibiting fungicides (Rubigan, Elite or Nova) and the strobilurin fungicides (Abound or Sovran), each class of fungicide should not be used more than 3 to 4 times (preferably 2-3 times) per season.
|
Summer Sprays Should Not Exceed a 14-Day Interval |
|
|
Third post bloom
spray |
(Strobilurin Fungicide) |
NOTE: A sterol-inhibitor fungicide (Rubigan, Elite or Nova) can be used postbloom for Powdery Mildew control; however, season long use of the sterol-inhibitors will greatly increase the risk of fungicide resistance development. Especially if early season disease control is good, emphasis for Powdery Mildew control later in the season should be placed on Sulfur, a Strobilurin fungicide (Abound or Sovran),a fixed copper fungicide or JMS-stylet oil.
NOTE: No more than 4 applications of a Strobilurin fungicide can be made per season.
NOTE: Watch the 66 days PHI on Mancozeb. If you get within 66 days of Harvest, Captan can be used in place of Mancozeb. The danger of black rot infection should be over by this time. Berries should be resistant to black rot. The Mancozeb or Captan is included for downy mildew control only. If downy mildew is a problem, the high rate of Sovran should be used.
|
Fourth post bloom
spray
These fungicide
choices |
(Strobilurin Fungicide) |
NOTE: If dry weather persists and the risk of Downy Mildew is low, Mancozeb or Captan should not be required and Sulfur can be used alone for powdery mildew control. If weather is wet and Downy is a problem, a Downy Mildew material needs to be included. A Fixed Copper Fungicide will give good control of both Downy and Powdery Mildew. Especially on susceptible varieties, powdery mildew will need to be controlled throughout the growing season.
NOTE: For Botrytis bunch rot control, the following fungicides are available:
|
|
Rovral
(1.5 lb/A) PLUS Latron B1956(6 fl oz/100 gal) OR Vangard (10 oz/A) used alone OR Elevate (1 lb/A) used alone |
These will be used only on bunch rot prone cultivars. The first spray should be made when disease is first observed or at veraison (or shortly thereafter). Then wait until a combination of threatening weather and/or disease develops and make a second spray (at least 2 weeks after the first spray). On late maturing varieties a third spray may be required.
NOTE: Some tests in New York have indicated that Rovral at 1 lb/A plus Vangard at 5 oz/A may have an additive effect and provides good bunch rot control. The use of a strobilurin fungicide during the bloom period may provide some control of Botrytis.
NOTE: The strobilurins (Abound, and Sovran) cannot be applied more than 4 times per season on wine grapes, and 3 times per season on all other types of grapes (juice). The label also states “do not apply more than 3 sequential sprays of any strobilurin fungicide before alternating with a fungicide that has a different mode of action”.