Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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SPRING 2012
GRAPEGROWING
In other words, against this specific disease, applying the label rate of a DFZ product is like putting on many times the label rate of Rally. Each fungal colony is different, but on average, it takes about 40 units of Rally to provide the same level of fungal inhibition as one unit of DFZ, which is why these latter products work better when both are used at comparable rates.
b. Vivando is a new product that received its first EPA registration in 2011. It is a fungicide that controls powdery mildew only, but has shown outstanding activity against this disease in our trials. For example, it provided 100% control on Chardonnay clusters subjected to extreme disease pressure: high carryover inoculum from the year before, no sprays whatsoever before bloom, untreated vines and those with various ineffective treatments scattered elsewhere throughout the block, 14-day spray intervals (Table I). Vivando represents a new class of chemistry, so there are no cross-resistance issues and it should be a very useful “big gun” addition to rotational programs with other materials.
c. Luna Experience is a new product that received EPA registration in February 2012. Like many new fungicide products, it is a combination of two active ingredients. The one that counts is fluopyram, a new “Group 7” material in the same class as boscalid (the non-strobie component of Pristine). It has shown excellent activity against both powdery mildew and Botrytis in several trials that we have run, which is consistent with results I have seen from a number of other locations. (The second component of Luna Experience is tebuconazole, the DMI active ingredient in the former product, Elite. Unfortunately, formulation of this new product is such that the lowest
labeled rate provides just a fraction of the tebuconazole that Elite once did, and it is unlikely to be of much benefit, especially in vineyards with any significant history of DMI use). CAUTION: At press time, fluopyram had not been approved for any wines exported to Japan.
Like virtually all new fungicides, the Group 7 materials are at risk of resistance development and must be rotated with other classes of chemistry in order to keep from burning them out. Remember, Luna Experience and Pristine both contain one of these materials, so should not be considered rotational products for one another.
2. Sulfur – We do not use dusting sulfur (too much rain), but sprayable formulations are very popular. A few years ago, we conducted numerous experiments with sprayable sulfurs to get a better handle on various aspects of their activity. A few highlights:
• Sulfur provides very good protective activity on sprayed tissues, but not on new leaves that emerge after the last application. No kidding.
• However, sulfur provides excellent post-infection control when applied up through the time that young colonies start to become obvious (about six or seven days at 80°F). Although it does have some eradicant activity against raging infections (see below), it is significantly stronger against the younger colonies. Practically speaking, this means that when a PM spore lands on a new, unprotected leaf produced since the last application (see above), there is still time to hit it with the next spray in a post-infection mode if that is applied thoroughly and before mildew is easy to see. Australian researchers have reported similar results.
• As noted above, post-infection sprays applied to heavily-diseased tissues are much less effective than
those applied to incubating or very young colonies. Sulfur is not the material of choice as an eradicant if you reach the “Omigod!” stage. That would be Stylet Oil or the similar PureSpray Green (or perhaps Oxidate, at a much higher cost).
Remember that once the leaf or berry cells beneath a well-established mildew colony have been sucked dry by the fungus, nothing will bring them back to life even if the mildew is eradicated. The best that an eradicant spray can do is to keep things from getting much worse, it cannot raise the dead. Never forget that the results you obtain will only be as good as the spray coverage you can provide.
• We were unable to demonstrate any negative effects of low temperatures on either the protective or post-infection activities of sulfur. In a number of repeated tests, control was the same at 59°F as it was at 82°F when we sprayed with the equivalent of 5 lb/A of Microthiol. Workers from Australia also reported no differences in control at 59°, 68°, or 86°F when used at this rate, although there was a slight decrease in activity at 59°F when the rate was reduced down to 1.7 lb/A.
• Rainfall of 1 to 2 inches decreases sulfur’s protective activity significantly. Not surprisingly, this effect is more pronounced with generic “wettable” formulations than with so-called “micronized” formulations (e.g., Microthiol), which have smaller particle sizes so adhere better to tissue surfaces. These latter formulations cost more for a reason. The negative effects of rainfall can be somewhat compensated for by adding a “spreader-sticker” adjuvant to the spray solution and/or increasing the application rate.