- Author: Lynn Wunderlich
Remember those 70°F days in early February? While you may have been basking in the California winter weather while your relatives back in the Midwest were freezing (sorry sisters!), our apple, pear, peach and nectarine trees weren't so happy. That is because pome and stone fruits need a certain amount of chilling during the winter to release them from dormancy.
Chilling has historically been calculated by summing the hours below 45°F or the hours between 32°-45°F from November 1 through the end of February.
When we look at the Camino CIMIS station's cumulative chilling hours below 45°F for 2017-2018, we can see that we reached only 855 chill hours during this time. Chilling requirements for pome and stone fruits depend on the variety, but most apple varieties that are not "low-chill" will require between 500-1000 chilling hours below 45°F, while most grapes will need less than 200 chill hours.
While February was unseasonably warm, late March and April has had some nights where temperatures have reached as low as 30-31°F. Once plants break bud, all of their tissue is susceptible to frost damage. Cold injury to grape green
Frost damage actually occurs because of dehydration of the plant cells. The cells are injured when their contents freeze and expand. Later, the damaged cells can no longer control their liquid contents, so they dehydrate.
The degree of frost damage depends on a number of factors: how cold the tissue got (depending on your site microclimate, slope, aspect, etc.); whether there is bare ground, which will absorb and hold daytime heat, or a ground cover or cover crop, which can not hold daytime heat and may even harbor ice nucleating bacteria that allow freezing to occur at slightly higher temperatures. The carbohydrate reserve that a vine has is also an important factor for susceptibility to frost injury. A low carbohydrate reserve, due to a super vigorous variety or one which stays growing late into the fall, or those that suffer from water stress (which is why it is advised to water post-harvest if you can), can make a vine more susceptible to frost injury.
Recently I observed variable frost damage in Viognier, Nebbiolo, Syrah and Gamay grape varieties growing in El Dorado County. It is still a bit early to determine how much damage (damage to emerging clusters) was done. Thankfully, basal buds and a "second crop" may come to the rescue! Erratic, intensive weather patterns, whether they be cold or warm, appear to becoming more common. Learning how to farm profitably during these uncertain times is but one of the challenges we face for our farming future.
- Author: Lynn Wunderlich
Vine balance is more than an academic concept. It is the foundation for making management decisions from planting time (rootstock choice, vine spacing, trellising type) to seasonal (irrigation, fertilizer, cover crop) and cultural options (canopy management, crop thinning) to harvest (grape quality and yield). It requires an in-depth understanding of your vineyard site
Also, as a special treat, Yorba Wines and Shake Ridge Ranch vineyard manager Ann Kraemer has agreed to come and share her techniques for estimating yield and adjusting fruit load. Ann is a knowledgeable and articulate speaker and I'm grateful to have a grower give practical advise.
All are welcome to attend Foothill Grape Day. To register, please go to: http://cecentralsierra.ucanr.edu/Agriculture/Viticulture/Foothill_Grape_Day_2018/
or contact Robin Cleveland, office assistant extraordinaire, at 530-621-5528, to sign up! I hope to see you there!
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- Author: Lynn Wunderlich
Happy New Year 2018 Fodder Folks! 2017 ended for me with a trip to South America, in order to participate
In Chile, growers are looking to sustainable farming methods.
Perhaps the most progressive thing that VSP wine group is doing to prepare for a sustainable future is communicating openly about their problems and solutions-because planning for a sustainable future doesn't happen in a bubble. Turns out it really is a small world, after all.
- Author: Lynn Wunderlich
The Charbono block that Dick had grafted over had a few shoots retained down on the trunk at the graft union which will need to come off for mech. harvest-these shoots were left to help devigorate the top so that the grafted bud wouldn't be shot out with spring flush. Kurtural noted that when grafting over from established rootstocks (this block was on 110R), there can be alot of vigor transferred to the scion in spring. Grafting over can also take place in fall, perhaps a safer time to make large cuts and avoid infection from canker disease. Vines need at least 10 days to grow a graft union and you want 6 inches of lignified shoot growth before fall frost hits. Of course, it isn't necessary to
The group then moved to take a look at the Gregoire pull behind machine Kevin Steward, vineyard manager with Trinchero Family Estates and Terre D'Oro Winery (located right across the street) generously brought over for the group to take a look at. The Gregoire had a "bow rod" head type of picking system, which means the fruit is shaken off of the vines using adjustable nylon rods. The berries fall down (without the rachis) onto Lexan or Nylon overlapping catcher plates that open and close as needed to work around vine trunks and trellis posts. The berries are then moved to the top with either a bucket or belt system. Trinchero has been using their machines for several years and is happy with
Lastly, we took a look at Dick's leaf remover-an Italian machine that sucks in the leaves and shreds them and spits them out the back. Dick loves this machine and uses it the day of harvest to cut "windows" into the thick canopies of his famously popular Barbera vines-making it easier for the pickers to find the fruit.
Is mechanization the answer for the labor issues facing the foothills? Looking at the numbers, it appears to pencil out, but some blocks are still too small, and too steep, and some winemakers and growers still prefer hand harvested fruit. As long as their are hands to do the harvesting.
- Author: Lynn Wunderlich
Hi Foothill Fodder Family! This week temperatures warmed up enough to begin the powdery mildew index in all of our 7 foothill PMI (powdery mildew index) stations-the information is publicly available on our UCIPM website here, with links on my webpages here. What does the index mean and how can we best use this information to begin our powdery mildew treatments?
I like to start by thinking of the disease "triangle": the 3 things needed for disease to happen. The key here is that all 3 of these parameters need to be in place for mildew to infect.
2. PATHOGEN. For infection to happen the pathogen needs to be present. There are 2 possible scenarios for every vineyard in spring:
Scenario 1: Mildew was present in the previous year AND/OR I have a highly susceptible variety. If you had mildew last year, or you have a highly susceptible variety (see above), then I always advise you start early-within 4-6 inches of shoot growth with an eradicant (i.e. horticultural oil at 1.5%), or apply a dormant or delayed dormant treatment (before budbreak) of lime sulfur, oil or micronized sulfur. If the problem was really bad, it may be a good idea to do both a dormant and an early treatment. The idea is to kill any of the overwintering chasmothecia spores and for this you need good coverage to contact those spores that are in the trunk and cordons crevices. This will greatly
Scenario 2: Mildew was NOT present in the previous year and varieties are not highly susceptible. The
By the way, there is new technology out there that uses lab sensing of fungal DNA (called "PCR" for polymerase chain
3. ENVIRONMENT. Powdery mildew is a living organism, even though we may not think about it that way. It grows at optimal temperatures, and at some temperatures-optimal is 70-85oF- it grows more quickly than at others. Mildew growth slows down or stops at high and low temperatures. That is the crux of the powdery mildew index, which accumulates points on a scale of 0-100 to indicate weather conditions that are optimal for mildew growth. The higher the score, the more quickly the fungus will grow as
To use the index well though, we really also need to look at our weather forecast-because this will help us predict how the index will change in the next week or so. Looking at the National Weather Service forecast, my preferred weather site, my crystal ball says the PMI will drop 10 points a day for several days this weekend and into next week; while rain with temperatures above 50 degrees will allow spores to germinate. I would GUESS that this next week will be our primary spore production period. If we had spore traps placed, we would be able to know better, so this is, again, only my best guess based on the weather forecast. Since weather can always change, I like to start my day (like every good farmer) looking at the NWS site to see our weather forecast.
I'll discuss more about current mildew conditions here in the foothills at Foothill Grape Day. I hope to see you there!