2011 Bud Break

Seasonal Overview

The 2011 season has started slow with growing degree days currently behind last year.  Bud break averaged several days to one week behind normal throughout the state and shoot growth has been slow.  The Central Coast experienced significant frost events and primary growing tissue has been damaged at multiple locations.  North Coast vineyards have had several frost events, however, no significant damage has been sustained.

Although trending behind last year, we are expected to catch up.  The La Nina weather pattern is breaking up and we are forecast to see more normal conditions as the spring progresses.  The next two weeks are expected to be warm throughout California with averages in the 70s.  With several days of above average temperatures we can expect more rapid shoot growth and development. 

The tables below illustrate growing degree days and precipitation data.  The current season is compared to historical averages and last year to give a relative idea of how we are tracking.

Grape Growing Degree-Days
March 15 – April 16
  This Year Last Year Normal* Actual Days Compared to Normal** Actual Days Compared to Last Year**
Mendocino County          
Ukiah NCDC (9122) 112 154 186 -8 -5
Hopland CIMIS (85) 105 127 143 -4 -2
Lake County          
Kelseyville 104 113 151 -5 -1
Red Hills 106 115 151 -5 -1
North Valley          
Manteca CIMIS (70) 186 204 241 -4 -1
Lodi CIMIS (166) 186 209 249 -5 -2
Oakville CIMIS (77) 183 179 224 -3 0
Santa Rosa CIMIS (83) 122 125 204 -12 0
Carneros CIMIS (109) 172 182 227 -5 -1
Central Coast          
Atascadero CIMIS(163) 176 165 233 -4 +1
Monterey County          
King City CIMIS (113) 176 210 249 -6 -3
San Benito          
Hollister CIMIS (126) 174 191 209 -2 -1

* “Normal” degree-days are calculated by taking the average of at least 5 years of historical data.

** Comparative columns illustrate actual days ahead (+) or behind (-) the current season is tracking with historical average and last year.  For example, a +1 in “Compared to Normal” illustrates the growing season is one day ahead of historical average.

Cumulative Precipitation (inches)
January, February, and March
  2011 2010 Historical Average
Mendocino County      
Hopland CIMIS (85) 17.6 21.0 17.9
North Valley      
Lodi CIMIS (166) 8.0 7.8 6.0
Oakville CIMIS (77) 23.7 20.8 19.2
Santa Rosa CIMIS (83) 18.6 20.0 16.8
Monterey County      
Kings City CIMIS (113) 9.8 8.9 6.7
San Benito      
Hollister CIMIS (126) 6.5 6.2 7.1
San Luis Obispo      
SLO CIMIS (52) 13.7 13.9 12.1

Napa, Sonoma

Andrew Nelson

This March was one of the wettest on record.  Over 13 inches of rain in Napa and 11 inches in Sonoma caused flooding in many vineyards.  The end of March brought two heat spikes and dry weather.  However, April has been cool and presented frost danger.

In Napa, growers have battled frost on several nights.  Time periods of 4 to 5 hours with temperatures dipping into frost potential have been mitigated with fans and overhead sprinklers.  Hail caused minimal damage to new green tissue in several sites but nothing of substantial impact.  In Pope Valley, frost protection has been used for long periods on two occasions.  One grower ran overhead sprinklers from midnight until nearly 11am on two consecutive nights.

Bud break is slightly behind with estimates ranging from several days to one week.  Degree day models show we are 3 to 5 days behind average and 1 day behind last year.  Shoot growth ranging from 1 to 6 inches.  Hillside Cabernet at Diamond Mountain Ranch shows about 1 inch in growth while earlier varieties on the valley floor are closer to 6 inches.  Sites with better drained soils are slightly ahead.  Growth has been slow the last week due to colder temperatures.  Growers are slow to get disking and mowing equipment into the field with soils still largely saturated.

During a March downpoor, this Vineyard in Yountville was almost completely underwater.

Mendocino & Lake, Northern Sonoma & Northern Napa

Terese Geniella

The growing season has been cool and rainy, off to a slow start, with only a few days in the 70s and 80s.  Frost nights have been few, most growers turned on less than 10 times, with 28°F the lowest temperature.  Rainfall is above average. Growing grounds are saturated.  Weeds are growing rapidly and growers are rushing to get disking and mowing completed.

Buds are out 2 – 8  inches, becoming shoots, with Cabernet in Lake County the farthest behind.  Consensus is the season is about 2 weeks behind normal, and expectation is that warm May weather will catch up vintage timing to normal.  The first round of sprays has started in the whites.  Clusters are mostly long, and doubles with wings, although it’s too early to see possible crop size.  Suckering will start in the next 2 weeks.

Lodi, Solano, Yolo and Contra Costa

Ron Pieretti

Over all shoot growth started off strong after the late bud break but slowed down after the weather changed to a cooler climate after our heat spike a few weeks ago.  In general we have shoots ranging from 4 to 8 inches in the warmer spots and 3 to 6 inched in the cooler areas.

Pest pressures are low with the cooler climate but I am still monitoring for symptoms.  One grower reports a new problem with snails in blocks that are close to cherry orchards with invasions nesting on stakes and posts then migrating to the vines to feast on the soft tissue.  None of this type of activity is noted in any of our blocks.

The frost event that we experienced a few weekends ago also had impacts in the Lodi and Delta area with some of our blocks being impacted.  Worst off appears to be some Chardonnay in Lodi.  The net loss is still too early to assess but about 20% of the block has tissue damage.  However, the end impact could be minimal because the fruit we usually drop after set could be equal to the losses due to frost damage.  Originally it was reported that our Zin Blocks in Lodi fared well but after further inspections some damage has been noted.  Again, net losses could be minimal because of our standard farming practices and could be mitigated by leaving canes that would typically be removed.  Viognier also initially reported no damage but we have become aware of some damage on the western edges of blocks with between 5-10% of the vineyard being impacted.

Monterey, Paso Robles

Matt Wilson

Paso Robles

Current vine growth is on average about 10 days behind normal.  Paso Robles forecast for the next 2 weeks is expected to be in the normal range with highs around 72-74°F and lows 42-44°F.  There was some significant frost damage around Paso.  Frost was sporadic and did damage to both red and white grapes throughout the area.  Many vineyards were not fully out when the frost event happened, so the extent of the damage is still being analyzed and time will tell how much crop loss there is.


Currently vine growth is on average about 10 days behind normal.  Monterey county forecast for the next 2 weeks is expected to be seasonally normal with highs around 68-70°F and lows 45-47°F.  There was some significant frost damage up and down Central Ave, Arroyo Seco and especially in San Lucas at our Paris Valley Road Vineyard.  Chardonnay was hit the hardest in Monterey County, but also other whites, Merlot, some Pinot Noir and Cabernet Sauvignon.  Vineyards that were damaged will be even further behind as they push new growth and crop levels will be affected dramatically.

Frost Damage in San Lucas at the Paris Valley Ranch. Temperatures were in the low 20s.


San Luis Obispo, Santa Barbara

Stasi Seay

San Luis Obispo

The weather forecast is calling for seasonable weather for the next ten days with no frost warnings.  Highs ranging from the mid 60’s to the low 80’s, low in the mid 40’s. Overall, the vine growth is behind ten days but should catch up quickly with warmer temperatures.

Santa Barbara

The forecast looks promising with warmer temperatures predicted. Highs in the upper 60’s to mid 70’s and lows in the low 40’s. Vine growth is behind a week but will catch up with continued warm weather.


European Grapevine Moth (EGVM)


Mothe on the Vine

This adult moth is camouflaged in the canopy.

The fight against the moth rages on, and it appears we are winning.  In 2010, for Napa County, there were almost 100,000 moths caught during the first flight (bud break), over 1,500 in the second flight (berry set) and under 300 individual moths caught during the third and final flight (verasion to harvest).  The steady decline of catches in 2010 was promising but the true test would be the number of catches in the first flight of 2011.  So far, there have been less than 10 individual moths caught in Napa County (compared to almost 100,000 at this time last year).  In addition, there are more traps being monitored this year compared to last (~8000 in 2010 compared to ~16,000 this year).  State wide catches this year have been limited to only Napa and Santa Clara counties, compared to catches last year in Fresno, Mendocino, Merced, Napa, Sonoma, Solano, Lake, San Joaquin, and Santa Clara.  UC Cooperative Extension research indicates that we are currently in the peak of the first flight which correlates to peak egg laying.  Growers are urged to spray now in a timed effort to target newly laid eggs and young larva.

Life Cycle and Control Methods

Larval Damage

When this egg hatches the larvae will feed on the flower cluster.

Larva from the third (and last) generation of 2010 overwintered underneath the bark and are currently emerging as adult moths.  These moths quickly mate and lay eggs on the cluster primordial (right).  These eggs hatch, and new larva feed on premature cluster tissue.  At the peak of the first flight (now), growers target spray programs on newly laid eggs (ovicide) and early life stages of new larva (larvacide).  Conventional growers are urged to spray Intrepid or Altacor (both are an ovicide and larvacide).   Organic growers apply a cultivated bacterium (Bacillus thuringiensis) that, when consumed by the moth larva, block the midgut and cause death.  However, Bacillus Thringiensis (Bt) has a lower residual control effect compared to conventional sprays (7 days compared to 21) and organic growers must spray more frequently to achieve the same coverage.

Pheromone Disruption

EGVM pheromone disruptor twist tie hung high in the canopy where mating occurs.

In 2011 there has been a large focus on pheromone mating disruption.  Growers are urged to apply pheromone emitters throughout the vineyard (200 per acre) which dispense the same pheromone that females produce to attract a male.  With enough “false” pheromone in the air, males are unable to successfully locate a female and mate.  Pheromone disruption is most effective when populations are low and males are dependent on locating a female by tracking her pheromone.  In dense populations males are able to locate females by site and pheromone disruption is not effective.  Pheromone disruption is considered essential to lowering current low populations to undetectable, with eradication being the ultimate goal.

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