I just saw Tony sent an email this afternoon to discuss about the sanitation issues. I want to add a few more comments here to discuss this important issue. (by the way, if you would like to be listed to Tony's email list which he also uses to publish his quarterly publication "Viticulture Note", please let me or Tony know)
Since we finished the season with long rainy periods, some of you experienced increased level of downy mildew and/or Botrytis. In addition, I have seen several outbreaks of ripe rot (which I will discuss in the next posting), and other general rots (sour rot, Aspergillus, Penicillium, etc.). Because of that, we probably have a higher risk of having these diseases in the next season. The question is how to deal with them.
As Tony noted, it is probably a good idea to move them from the vines and place them in the middle of the row, then remove or mow. If the berries are hanged in the trellis, these can be sources of inoculum in the next season. Since many of these pathogens are splashed by rain, having a large number of spores right next to new growths is a bad idea. Also, by mowing the debris, it will help decomposition of these infected tissues. I have seen berry debris directly under the vines that were covered with Botrytis spores in the spring. Since there were no green tissues around, I do not know what it meant in terms of disease development for the season, but it just made me realized that they do survive through the winter in these tissues.
The question is what you can expect from these sanitation measures. Unfortunately, many of grape pathogens can complete their lifecycle in a short period of time (2-4 weeks), thus the effect of sanitation does not last long. Therefore, even if you do a good job of cleaning up your vineyards, it will not allow you to skip any of early season sprays. However, it will help reducing the risk of outbreak early in the season. If the environmental conditions were very favorable and there were abundant spores, you may face the risk of outbreak from the get-go of the season.
Tony covered about cluster, but how about canes and pruning woods? The same principal will apply here. However, the difference is that these woody tissue are more resilient to decomposition, and some of pathogens, such as Phomopsis, Botryosphaeria, and Eutypa can survive in the woods for several seasons. Since both Phomopsis can Botryosphaeria can produce spores from the infected 1st year cane, if you leave them on the ground, chances are they can be the source of inoculum for the next season. Spores of both pathogens are splashed by rain (some of Bot species can produce airborne spores, but it seems that rain splashed spores are the majority), thus, the closer the canes to the main trunk, the higher the risk is. Say, if you have infected canes nearby trunk and the trunk is damaged from winter injury or other means of wounding event, you can easily imagine that these pathogens move into the wound and cause problems later. Thus, it would be nice to remove pruned canes from the vineyard, or at least chop them down in the middle of the row.
If you are making a big cuts, make sure to take them out from the vineyard. You are cutting big pieces probably because of diseases, and leaving these old trunks or cordons in your vineyards won't do any good for you.
Friday, October 21, 2011
Friday, October 7, 2011
I just learned that Fenarimol (Rubigan® AS, Vintage® SC and Focus®, from Gowan) will be taken out from the market soon. It was due to their business decision. The company will sell and support the fenarimol brands Vintage SC and Rubigan AS through December 2012. Gowan is in discussion with EPA to voluntarily cancel its fenarimol registrations.
The distribution channel typically has 2 years from the official date of cancellation to sell existing inventory of fenarimol products. Growers typically have no time limitation to use up fenarimol products they have purchased. (Please remember to keep and follow the label!)
It is sad to loose a good product that can be an alternative option for our powdery mildew. It belongs to group 3 in FREC code (Sterol Inhibitors or SI), thus, the mode of action is the same as other SI's, such as tebuconazole, myclobutanil, etc.