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Grape IPM in the Northeast

IPM Disease Management Protocols

Postinfection, Primary-Season-Only Spray Protocol for Concord

Sprays are timed according to the presence of the powdery mildew (490k pdf file) and black rot (548k pdf file) inoculum and the occurrence of an infection period. An infection period occurs under the following conditions: 1) For powdery mildew, approximately 0.1 inch or more of rain and temperatures equal to or above 50°F, or 2) any amount of rain and temperatures during the period of leaf wetness that are suitable for black rot infection (see table 3 below).

Table 3. Leaf Wetness Duration and Temperature Necessary for Infection
by the Black Rot Fungus ("Spotts Chart")

Temperature (°F)

Hours of Leaf Wetness Required for Infection

45

no infection

50

24

55

12

60

9

65

8

70

7

75

7

80

6

85

9

90

12

Table by R. A Spotts, Ohio State University. Reprinted with permission.

Monitoring of weather conditions for infection periods should begin at three inches of shoot growth. Once an infection period for either black rot or powdery mildew has occurred, the following fungicides should be applied within 72 hours after the start of the infection period. Nova at 4 oz/A should be used in combination with an EBDC (Manzate, Dithane, etc.) at 3 lb/A in all prebloom, postinfection sprays. After this fungicide application, a 14-day interval should pass before additional treatments are considered. Infection periods that occur within that interval should be ignored. Weather monitoring should continue in order to time fungicide applications in accordance with infection periods until the supply of black rot ascospores is nearly exhausted, or when berries are 5 mm in diameter (pea-size). The Nova label states that a maximum of 21 days of protection is provided for powdery mildew. If no infection periods have been recorded after 20 days and berries have not reached 5mm in size, another Nova application at 4 oz/A should be applied. Continue monitoring for infection periods after 14 days or until berries reach 5mm in size.

One disadvantage of the postinfection program is that there are no postinfection fungicides that will manage Phomopsis Cane and Leaf Spot (277k pdf file) or downy mildew (300k pdf file), and protectant applications for them are not a part of the protocol. Phomopsis and downy mildew can be maintained at low levels using this protocol in low-inoculum vineyards and in years that do not favor severe infections. However, if a vineyard has a history of severe Phomopsis or downy mildew infections, a primary-season protectant disease management strategy should be used.

An example of how the postinfection disease management protocol has been used successfully in grower vineyards is illustrated by figure 4 below. This figure shows infection periods and wetting periods as they were recorded during the 1994 growing season at the Lake Erie Center for Grape Research and Extension (LECGRE), Fredonia, New York. Wetting periods are rain events that produce leaf wetness but do not provide conditions necessary for disease germination and infection. Bud break occurred on May 2, with 3 inches of shoot growth in some areas by May 5. Three inches of shoot growth is the "trigger" to start monitoring for infection periods in Concord vineyards with a history of black rot or powdery mildew. Vineyards without a history of problems with these diseases can wait until 10 inches of shoot growth.

Figure 4.

An infection period for powdery mildew occurred on May 5. This required a tank-mix application of Nova at 4 oz/A and an EBDC (Manzate, Dithane, etc.) at 3 lb/A within 72 hours after the 9 p.m. start of the infection period on May 5. As shown in figure 4, a fungicide application was made on May 6. Four ounces of Nova provides 14 days' protection against black rot and powdery mildew. While the Nova label states that 21 days' protection is provided for powdery mildew, monitoring is resumed after 14 days due to the loss of protection for black rot. Therefore, no monitoring for infection periods was required until May 21.

An infection period occurred on May 26, resulting in the need for a second Nova/EBDC application. Once again, no monitoring took place for 14 days. On the fifteenth day following the fungicide application, weather conditions were again monitored for conditions suitable for infection by black rot or powdery mildew. An infection period occurred on June 13, followed by a third Nova/EBDC application on June 14. The official date of bloom at the LECGRE was June 19. This date has significance because some processors allow EBDCs to be used only from bud break to the time just prior to bloom. As shown in figure 4, the June 14 fungicide application provided protection to the shoots and leaves for the bloom and immediate postbloom period, during which six of the seven late-June infection periods occurred.

The seventh infection period on June 29 required a fungicide application of Nova at 4 oz/A and Ferbam at 3 lb/A (used due to the restriction on EBDCs). This was the fourth and final spray, as this application provided protection past the time of pea-size berries.

When the growth stage of pea-size berries is reached, primary inoculum of black rot and powdery mildew are expended. With good early-season protection, little or no primary infection should occur. This should, in turn, severely limit the amount of secondary inoculum. Concord growers using the postinfection spray program during the 1990-1994 growing seasons achieved management of powdery mildew and black rot equal to or better than that provided by their conventional fungicide programs.

Figure 5 (below) shows a typical grower adaptation to the postinfection disease management protocol. Many Concord vineyards historically have low levels of black rot and powdery mildew at harvest and therefore low levels of overwintering inoculum. Growers with these vineyards do not need to start applying fungicides until the 10-inch growth stage. In figure 5 growers have waited until the 10- to 12-inch shoot growth stage to begin monitoring for black rot or powdery mildew infection periods. An infection period occurred on May 15, followed by an extended wetting period - but not an infection period - caused by sporadic rainfall on May 16. A Nova/EBDC fungicide application was made on May 17. Monitoring of infection periods began June 1, detection occurred on June 6, and another Nova/EBDC application was made on June 7.

An infection period on June 23 resulted in a third fungicide application of Nova and Ferbam. While this application only provided protection against powdery mildew and black rot until July 9, there were no more infection periods detected before the growth stage of pea-size berries was attained on July 10. Similar postinfection programs starting at 10 inches of shoot growth have been used by growers in the Lake Erie region and have provided equal or improved protection against powdery mildew and black rot when compared to their conventional disease management programs during the 1990-1994 growing seasons.

Figure 5.

Postinfection Spray Protocol for Niagara and Certain Hybrid Varieties

This program is useful in varieties that have a susceptibility to black rot and powdery mildew similar to that of Concord, but with an increased susceptibility to downy mildew and/or Botrytis. The postinfection, primary-season program will be the same as that used for Concord. This program is to be used until the prebloom period. (Depending on weather and growth conditions, the prebloom period could be anywhere from 3 to 10 days prior to bloom.) Sprays are timed using the Spotts Chart for black rot or the powdery mildew model of at least 0.1 inch of rain at a temperature of 50°F or higher.

First Spray
Starting at three inches of shoot growth, weather is monitored, and Nova is applied at 4 oz/A within 72 hours after the start of an infection period for black rot or powdery mildew (as determined by the Spotts Chart for black rot or the powdery mildew model of 0.1 inch of rain and temperature of 50°F or above).

Second Spray
After waiting 14 days, monitoring of weather conditions for black rot or powdery mildew infection periods begins. When either occurs, Nova is applied at 4 oz/A. Do not allow more than 21 days to elapse between the first and second fungicide applications. Label restrictions do not allow for more than 21 days to elapse between applications of Nova.

Other Prebloom Sprays
Same protocol is followed as for the second spray.

Immediate Prebloom Period
This application will be a postinfection application of Nova (4 oz/A) + mancozeb (3 lb/A) or as a protectant application if no infection periods for black rot or powdery mildew have occurred immediately prior to bloom. In other words, a Nova + mancozeb spray needs to be applied prior to bloom for downy mildew, powdery mildew, and black rot protection through bloom. Ridomil MZ may be substituted for mancozeb for this spray.

Postbloom Sprays
These will be driven by a downy mildew sporulation model, if available, and the occurrence of black rot or powdery mildew infection periods. The postinfection disease program will be terminated when berries have reached pea-size (5mm). Neogen and METOS weather equipment have downy mildew sporulation models available. If no downy mildew models are available and conditions exist for downy mildew infection, fungicides should be applied based on a protectant program. Applications of an EBDC, captan, Ridomil/MZ 58, Ridomil/ copper, or copper + lime can be used for downy mildew. Sulfur, copper + lime, JMS Stylet Oil, or a sterol inhibitor can be used for powdery mildew. Check processor restrictions before making an EBDC or captan application. Do not apply Nova, Bayleton, or Rubigan in vineyards with existing severe powdery mildew infections.

Supplemental Management of Botrytis on Susceptible Cultivars or in Vineyards With a History of Botrytis Infection

Disease Management Protocol for Vinifera and Highly Susceptible Hybrid Cultivars

This program is designed to provide excellent management of primary infections of powdery mildew, black rot, and downy mildew, and of fruit and rachis infections of Phomopsis Cane and Leaf Spot during the period of susceptibility. This should allow cessation of black rot management after the first postbloom spray, cessation of Phomopsis sprays, cessation of downy mildew sprays unless scouting reveals the need to manage additional secondary spread later in the summer, and relatively inexpensive management of secondary powdery mildew during the summer. This is also a good resistance management program for powdery mildew. Midsummer outbreaks of powdery mildew (very unlikely if protocol is followed) should be responded to with JMS Stylet Oil, not the sterol-inhibiting fungicides.

First Spray
Starting at three inches of shoot growth, monitor weather and apply Nova at 4 oz/A for black rot and powdery mildew within 72 hours after the start of a powdery mildew (PM) or black rot (BR) infection period. Add mancozeb at 3 lb/A if there is a history of Phomopsis (Phom) infection.

Second Spray
Fourteen days later, apply Nova at 4 oz/A for BR and PM.

Third Spray (Prebloom)
Fourteen days later, apply Nova at 4 oz/A for BR and PM + mancozeb at 3 lb/A for downy mildew (DM) and Phom fruit infection or apply Rubigan at 3 oz/A + mancozeb at 3 lb/A.

Fourth Spray (1st Postbloom)
Fourteen days later, follow the same protocol as for third spray (prebloom).

Fifth Spray (2nd Postbloom)
Ten to fourteen days later, apply sulfur for PM and, if rainfall is abundant, mancozeb at 4 lb/A for downy mildew.

Midsummer Sprays
Apply sulfur for PM at 7- to 14-day intervals through veraison when needed as indicated by scouting or apply JMS Stylet Oil to eradicate existing powdery mildew infections. Captan or copper + lime may be used for downy mildew if scouting indicates a need.

Supplemental Management of Botrytis for Susceptible Cultivars or in Vineyards With a History of Botrytis Infection

Primary-Season Protectant Disease Management Strategy

This protocol can be used in place of the postinfection disease management protocol for varieties that are susceptible to black rot, Phomopsis Cane and Leaf Spot, and/or downy mildew, but not powdery mildew. This disease protocol attempts to greatly reduce the amount of primary infections through early-season fungicide applications, as does the postinfection protocol, using a protectant schedule. However, this protocol does not provide management of powdery mildew prior to the prebloom application. Therefore, it should not be used in vineyards with a history of powdery mildew infections or in vineyards with highly susceptible varieties (see table 2, 69k pdf file) for varietal susceptibility to this disease). This protocol will result in four fungicide applications being made each year.

Timing

Fungicide Applied

 3 inches of shoot growth

 EBDC

 14 days after first application

 EBDC

 14 days after second application (prebloom)

  SI* + EBDC

 14 days after third application

  SI* + EBDC or Ferbam or Ziram

 * SI = sterol inhibitor (Bayleton, Nova, or Rubigan). Rubigan should not be used as the sole fungicide for management of black rot under conditions of heavy disease pressure.