What happens when grapes get wet feet.

After three years of very dry winters in Sonoma County, the rain has returned.  This is all good to a certain extent, lord knows we need the water.  The reservoirs are full and some are even over 100% of “normal” capacity.  However, there may be a big downside, at least as far as us winos are concerned.  By now the skies of Sonoma County should be blue and the weather should be warm.  Alas, it’s another gray, wet day here in Northern California.

Okay, so what?

Wet Rows

These vineyard rows are in Windsor, California, in the Russian River Valley.  In an effort to help with the saturated ground the vineyard manager and viticulturist decided to have the rows rotor-tilled to try and dry out some of the water.  Of course we’ve had nothing but rain, rain and more rain, so now there’s just a big sloppy mess!

So grapevine biology is, well, just like anyone else.  They are here to procreate.  Yeah, grapevines need to get busy just like the rest of you.  Pollination of grapes is a little different than your average fruit tree or flower.  Grapevines are self-pollinating.    They have both the boy parts and girl parts (no snickering in the back!).  They pollinate them selves via the air that blows across the baby clusters when they “Flower.”  Here’s the rub, it’s been raining like crazy and the rain is washing the pollen off and it’s quite possible that a good deal of grapes will not be fertilized and therefore will not seed.

Okay, still… So what?

Clusters are Flowering

Grapes that don’t produce seeds never make into full fledged berries.  The grapevine doesn’t want to waste energy into grapes that bear no seed.  So that berry-to-be shrivels up dies, this is called shatter.  Multiply this effect because of the rain and you can see what kind of effect this could have on a growing season.

Oh NO!

Chardonnay Vines

Compound this shattering effect with additional water on fruit and you get mildew.  Yuck!  This is a tenuous situation at best, and there’s little we can do but hope for better weather (no more rain please Mom).

So, what’s up Doc?

I checked in with local expert, Dr. Marilark Padgett-Johnson, an instructor in the wine program at Santa Rosa Junior College (you can find her here: http://online.santarosa.edu/homepage/mpadgettjohnson/).  By the way Santa Rosa Junior College is a great resource for any folks who are local to Sonoma County. They offer classes from Viticulture to Oenology, and from Wine Judging to Component Tasting.  If you can I highly recommend taking advantage of this outstanding resource… Okay, enough of a plug for SRJC, on with the schooling.

image from SRJC website

She says that the PM (powdery mildew) is the greatest concern at this point.

“More of an issue are the threats of powdery mildew (PM), spring time Botryis Cinerea hits on shoot tips and foliage, and phomopsis.”

I had to look up phomopsis, here’s a good article I found from Michigan State Extension, Van Buren County http://www.canr.msu.edu/vanburen/phomop.htm

“PM an issue because it’s challenging to get into the vineyards and spray fungicides when the soil is wet, and the rain potentially washes off the spray material if applied.   Botryis Cinerea, and phomopsis are fungal diseases that flourish during wet springtimes.”

It is what it is!

Yeah, still.  Grape farming is just that, it’s taking what mother nature deals you and doing the best you can.  There have been many previous rainy seasons that have turned out some fabulous crops and excellent wines.  Here’s an excerpt from 2005, a great wine year:

Source : http://www.farmersalmanac.com/weather-history/94928/2005/05/25/

As you can see in 2005 on this day it was 84, now that’s what I call great Spring weather, instead today we have

Source: http://noaa.gov

A few more days of rain are in the forecast and we here in Sonoma County are all crossing our fingers and hoping that we’ll get some more seasonable weather.

I hope this is some good information for you all and that you send some sunny wishes our way, we could sure use them!

Cheers,
Brian

Tags: biology, flowering, grapes, powdery mildew, rain, shatter, vineyard managment, Viticulture