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Fungal disease management throughout the growing season

The following table was developed as a means of summarizing the information provided in OMAFRA Publication 360 - Fruit Production Recommendations 2010-2011, including new products for 2011 and highlights the periods during the growing season when specific diseases may be a problem and which fungicides are recommended at a particular growth stage. This will vary somewhat depending on the susceptibility of the grape variety, the weather conditions and the history of disease in the vineyard. In some cases, a fungicide may be labeled for the full season but is not recommended to be used that way for resistance management. Table 6-5 in OMAFRA Publication 360 gives more information on the relative effectiveness of these fungicides. The main purpose of this table is to give some idea of the fungicide combinations/mixtures that may be used throughout the season to manage specific diseases present in your vineyard. However, this table is not meant as method of indicating compatibility of products in a spray mixture. You should read the label to determine whether a fungicide will cause injury (e.g. burning or discoloration) on a particular variety or under specific drying conditions and also whether specific tank mixes are not recommended. (See Table 6-5 Publication 360 as well as fungicide labels.). It is also important that you confirm that a particular fungicide is acceptable for use by your processor and follow their pre-harvest intervals for individual pesticides

How to use this table:

The table is broken down by growth stage and within each growth stage the diseases that require controlling are listed. If a disease is bold italics (+) it is of primary concern at that growth stage. For example, at 80% bloom to immediate post-bloom, powdery and downy mildew and black rot can infect the berries (and leaves) while Botrytis is a risk only in susceptible varieties. At berry touch, powdery and downy mildew should still be controlled on the foliage but Botrytis infection of fruit is of special concern at this stage.

While several of the fungicides are labeled for use throughout the season and are listed throughout the calendar in Publication 360, in the table below they are recommended at specific growth stages. For example, Nova, Flint, Sovran, Pristine, Lance, Revus, Presidio, Vivando and Quintec are recommended specifically during the period when fruit are susceptible to powdery and downy mildew and black rot, that is, as soon as the caps fall until berry touch. These products are our "big guns" and should be used to keep the fruit disease-free. It is also important to be sure to maintain tight spray intervals during this time to ensure that the berries are protected. Unless the weather is very dry, do not stretch spray intervals beyond 10 days during this time.

The growth stages listed are a guide. Generally, you should keep a 7-day interval between sprays (unless it gets cold) from your first spray until berry touch. New growth will not be protected from infection if you stretch beyond this interval. Once the period for fruit infection is past, you can usually stretch spray intervals to 2 week intervals.

Printable version of table

A few things to note:

1. A general rule of thumb is that half of a protectant fungicide is washed off with 1" (25 mm) of rain and the spray interval should be shortened and if 2" (50 mm) of rain occurs, the fungicide should be reapplied. This is especially important if the rainfall (or irrigation) occurs within 24 to 48 hours of the pesticide application. Nova, Flint, Sovran, Pristine, Lance, Revus and Ridomil Gold MZ move into leaves and fruit so are not prone to rain wash-off one hour after drying. Only Ridomil Gold MZ will move from treated leaves to untreated leaves and fruit. However, do not rely on systemicity of these products to compensate for sloppy spray application!
   
2. The Phomopsis spray at 1-3 leaves is necessary only if there is a history of Phomopsis problems in the vineyard.
   
3. Ridomil Gold MZ may be applied once pre-bloom and once post-bloom with a 66 day PHI.
   
4. Dikar will available for sale until the end of 2010. It will be registered for use in Canada until 2012.
   
5. Revus, Nova, Flint, Sovran, Pristine or Lance should not be applied once the disease is visible as this will promote the development of resistance. Switch to multi-site (M) fungicides and protect uninfected tissues.
   
6. Black rot was more of an issue than usual in some vineyards in 2009. The critical period for black rot control of fruit is from immediate pre-bloom through 4 weeks post-bloom. In vineyards where severe black rot developed in 2009, or if the vineyard has a history of consistent black rot development, an additional spray two weeks before bloom may be beneficial, particularly under wet conditions. Because damaging levels of black rot usually result from spread within the cluster, sprays should continue through the end of July if more than a trace level of berry rot is present and weather conditions are suitable for infection.
   
7. The fungicides labeled for botrytis bunch rot are very specific in their mode of action. The importance of the bloom period sprays varies from one year to the next and among varieties. In years with a wet bloom period, the bloom sprays can make a significant contribution in reduction of bunch rot later in the season. In years with a dry bloom period, the best effects result from botrytris sprays applied from bunch closure through veraison. Pristine will probably provide adequate protection from botrytis bunch rot infections at bloom if it is used at the 80% cap fall to immediate post-bloom period, but it must be followed up with a good fungicide program at berry touch and veraison ("s" for "suppression" in the table). In the past, it was assumed that the period between fruit set and bunch closure was relatively "safe" for bunch rot infections. However, sporulation of Botrytis on hail-injured berries while they were still green in 2008 and 2009 showed that latent infections that occurred at bloom may be activated when fruit is injured well before it reaches veraison.