A call from a small grower, surprised at the sudden decline of the avocado trees. It must be a disease was the grower's thought. Well driving up to the site, there were numerous trees with canopies indicating drought stress. In fact most of the trees looked like they had had the water turned off. When I got to the orchard, all the trees had a similar look (see photo below). The fringe of the canopy had turned brown/red where the leaves had collapsed rapidly, while the interior leaves were often still green. All the trees had a similar cast. It turns out the water district had required a cutback just when temperatures were going into the 100's. NO water, no cooling effect of transpiration and the outer fringe of leaves collapsed. This is called the “clothesline” effect. It's like a sheet on a clothesline where the margins of the sheet dry first and gradually the body of the sheet dries. The same thing happens in a canopy. The outside leaves are the first to dry out and then the rest of the canopy goes. When you see a whole orchard go down suddenly, that does not fit into a disease pattern. There's usually an epicenter where it starts – where it's colder, wetter, dryer, hotter, more overgrown, etc. and spreads out from there if it is going to spread. It turns out that the automatic irrigation system had gone down and the grower hadn't noticed until too late. When you see reddish tinged leaves, it means the leaves went down fast. When they are brown, it means they slowly went down over weeks or months.
With all the dead points in the tree, it is now open to disease – twig/leaf blight caused by one of the Botryosphaerias. These decay fungi are everywhere in an orchard decaying organic material on the orchard floor. With the dead material in the tree, now the tree becomes a potential feast for the fungi. The dead stuff has to come out, or the fungus will start eating into the tree. I suggested that instead of pruning out all those little points of death, that they cut back the whole canopy to major scaffold branches. In doing so, it would rapidly and cheaply remove the dead material and reduce the water demand.
CACHUMA RESOURCE CONSERVATION DISTRICT
FOR SANTA BARBARA COUNTY GROWERS AND FARMERS
WATER CONSERVATION FUNDING AND TECHNICAL SERVICES WORKSH0P
8:15 Breakfast and Technical Displays
9:00 Grower and Funding Talks
10:40 Discussion and
Monday, June 27, 2016 8:15 -11:30 am
Rincon Beach Club
3805 Santa Claus Lane
Hear from growers who have used State and Federal funds to improve water use and operational efficiency and lern about new resouce conservation technologies from local agricultural and technical service providers.
Advance registration not required. For more information:
Anne Coates 805-455-2820 www.waterwisesb.org
Jamie Whiteford 805-764-5132 www.vcrcd.org
Water woes are probably not going to go away, so readup on how to best manage water at this new blog.
- Author: Rachael Long
Guest post from Rachael Long, UC Cooperative Extension Farm Advisor, Yolo County
The Yolo County Flood Control and Water Conservation District (YCFC) is an agency that supplies water to farmers in northern California. The agency is at the forefront of innovative efforts aimed at banking groundwater by diverting flood waters into their unlined canals. This gives flood waters time to infiltrate soils and recharge groundwater.
Using a water right permit that they recently obtained from California's State Water Resources Control Board, flood waters from recent storms are being captured from Cache Creek as it enters the Sacramento Valley. YCFC recently opened their lateral gates, allowing the flood waters to...
Groundwater wells can fail in many ways. Sometimes the water table sinks below the level of the well. Sometimes minerals cause buildup in well systems. And, sometimes, wells get clogged with lots and lots of microbes.
Microbes can form large, jelly-like mats that lead to well failure from what is known as biofouling. Biofouled wells can be both expensive and technically challenging to repair. There are even times that repair is not possible and replacement is the only option. In Washington State, for example, researchers have encountered well pipes completely clogged by mats of bacteria....
California's Sacramento-San Joaquin River Delta region, commonly referred to simply as the Delta, is often described as a unique part of the world. Although it is located between two big urban centers – the greater Sacramento and San Francisco Bay areas – the Delta can feel like another world altogether.
This is something Michelle Leinfelder-Miles, a farm advisor with UC Agriculture and Natural Resources, knows well. She comes from a sixth-generation farming family in San Joaquin County and, after accepting her position several years ago, was happy to return “home”...
The California drought has shined a spotlight on stories of people and communities living without water. Unfortunately, lack of access to clean and affordable water is not a new issue. Water security has been an enduring challenge across the state in wet and dry years alike, particularly for disadvantaged communities. Trying to meet concerns about water availability and affordability with pragmatic action is where things get both complicated and interesting.
One approach that the state has invested a great deal in exploring is known as integrated regional water management. While it is a complex topic, the basic idea is that there are multiple needs for water throughout the...
Street-side stormwater facilities are turning runoff once seen as a nuisance into a resource. Also known as bioretention areas, rain gardens, and bioswales, these small stormwater facilities provide a decentralized approach to alleviating peak stormwater runoff and subsequent flood damages. These are particularly critical functions in cities like San Francisco where the storm and sanitary sewer systems are combined because they help managers to prevent dreaded “combined sewer overflow” events. As a bonus, stormwater facilities have also proved useful in promoting groundwater recharge and filtering pollutants as water percolates through soils.
While street-side facilities are effective in helping to manage...
As fruit gets heavier and heavier on a tree, does the tree use more water? Or is it sensitive to more water stress? It's not clear if there is a difference. We've all seen a lemon tree sigh in relief after the crops been pulled off. And avocado trees last summer that got hit by the Santa Ana seemed to be more affected the more fruit they had. In fact, about two weeks after the wind blew, many trees with a heavy fruit load showed clear signs of salt burn or leaf blight.
Now according to work done on olive, the trees actually need more water to avoid stress. In an Israeli study they measured water use by olive trees with and without fruit and found that there was significant more water use when fruit was present.
This is a lot more than we usually allow for in our irrigation scheduling. Often we don't adjust at all for fruit load. As fruit sizes most growers do recognize this as a period when stress might cause fruit drop and pay more attention to the trees, but may not alter the irrigation cycle.
Fruit have stomata just like leaves do, so they do lose water. Losing too much water leads to flaccid fruit and in the case of avocado easy fruit dehydration and drop. So we know it's a sensitive period, but maybe we need to be irrigating more frequently. That's where soil moisture measuring devices help adjust the schedule. If they are using more water, then irrigate more frequently.
We'll be doing some work over the next few years to verify this. Stay tuned.
At a recent meeting in Modesto covering drought and how it is being dealt with around the world, there was an interesting presentation by some Israeli researchers. They looked at the use of recycled water from sewage treatment plants and the use of desalinated water from the Mediterranean. The recycled water had much of the original mineral nutrients, but had been treated for microorganisms. They wanted to know how much of the nutrients could be accounted in the fertilizer balance applied to apple, pear and nectarine orchards. Their conclusion that after one year, there was a significant contribution and that leaf analysis had not changed, not yields after applying the effluent. This was only for one year, but I could imagine that after many years there would be a significant impact.
They also looked at desal water, and found that the process removed most minerals except for boron. They actually found that plants irrigated with this water ended up with calcium and magnesium deficiencies and more boron toxicity. The reverse osmosis membranes used in this case were not very effective at removing boron. In the case of many waters north of Los Angeles there are often high levels of boron in the water, and using RO water might accentuate the problem.
RO water also is usually too pure and the lack of salt causes soil to deflocculate - lose structure. Yes, you need some salt to have a healthy soil.
Read more about this trial at:
Bitter Pit in Apple caused by low Calcium