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Viticulture Association of the Santa Cruz Mountains

  Bloom I

Map with permission of VinMaps



Itís hard to believe that we are already into the middle of May. The late winter rains over-stayed their welcome and allowed Spring to sneak in barely noticed. Nevertheless we are looking at that time of year when the need for powdery mildew control is absolutely essential.  If you can get through bloom and fruit set with-out mildew your summer will be far more enjoyable.  Remember that powdery mildew is not always obvious in the early stages. By the time you see the powder your vineyard has already built up quite a population and eradication efforts are required.

The rains this year have made the spray program quite challenging. It is my opinion that the standard suppressant program of Thiolux or other sulfur programs might provide limited protection because they just keep getting washed off. Eradicant products like JMS Stylet Oil or Armicarb or Kaligreen (doesnít last as long on the foliage) are very effective tools against mildew in a year like this. They wash off too, but at least they kill off the spore populations before they go. That way there are fewer spores to be distributed by the rain. As always, thorough coverage is essential. These products are not systemic and are only effective on foliage they come in contact with.

Be sure to include a botrytis control spray in your program during bloom and at set.  Serenade is an organic product available for this purpose. Elevate and Vanguard are among the alternatives.

In addition to sprays it is very beneficial to focus on improving the canopy microclimate. 

Shoot thinning is an essential practice this year in most vineyards.  If your vineyard tends to have extra vigor, late season shoot thinning will not only open up the canopy but reduce vigor as well. Make sure that your canopy allows plenty of light and air to surround the developing flower clusters. This allows them to dry out from the rains, reduces humidity within the canopy, and allows spray penetration and good coverage. Sprays are far less effective if you donít achieve good coverage.

On another note, Juan Hidalgo from the Santa Cruz County Ag. Commissionerís Office passed out mealy bug traps at the last meeting. Hopefully everyone has deployed those traps in their vineyard. If you have, please remember to bring the trap to the next meeting. We will gather them up and turn them in for examination. New traps will be available

at the same time. Turn in the trap even if you donít see anything in it Ė it will still help the Ag Department track the spread of the bug, or lack of it. Letís keep up with this program and keep Santa Cruz free from this pest. There are a number of control programs available if you do have mealy bugs, so get informed and take action before they corrupt your fruit.

This is the perfect year to consider a no till policy in your vineyard. With all the rain it may be wise to simply keep the ground cover tightly mowed and avoid tilling or discing. Tearing up the soil not only disrupts microbial life in the soil, it also makes it harder to drive the rows, it compacts the soil, it wicks up even more moisture from deeper in the soil profile, and it creates a dustbowl in late summer. Focus on weed control under the vines and keep the aisles closely mowed to discourage mites and other pests. Newly planted vineyards may require a different approach.

Remember to take petiole samples at full bloom. Doing so will tell you the nutritional status of the vines in real time and is an excellent aid making decisions about nutrient supplements at fruit set and later.

Despite the rain, I hope that everyone is enjoying a bountiful spring. It is the best wildflower year in ages. Make a point of taking in all the beauty that each season brings. It is such a gift to be here.

Happy Spring.

Prudy Foxx
President, Viticulture Assn. of the Santa Cruz Mountains

(Vine Talk column, May 2005)

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