Posts Tagged: avocados

Climate change may reduce frost damage to orchard crops

CalAgroClimate web tools help farmers prepare for frost events

A cold snap damaged almond blossoms across the Central Valley, resulting in more than $44 million in crop insurance claimsin late February 2018. A multi-day frost event wiped out roughly 75% of California's citrus crop and severely damaged avocados in January 2007. Frost can damage crops, impact growers' bottom lines and drive up food prices for consumers. With advance notice, farmers may be able to use heaters, wind machines, irrigation and other tactics to lessen some of the impacts of cold weather, such as damaging near-ripe citrus fruit or killing the bloom in almonds.  

CalAgroClimate is a new farmer-focused website that can help growers anticipate weather-related risks and make plans for taking defensive action. Growers and crop consultants can use CalAgroClimate's crop and location-specific tools and resources to help prepare for upcoming frost events. The website's tools can also support on-farm decisions for managing heat, crop development and pests. 

Future holds less frost

The risk of frost damage to crops and the need to prepare for that risk is top-of-mind for many farmers today, but will it always be so? To examine what climate change might mean for future frost risk, researchers at UC Davis, UC ANR and the USDA California Climate Hub conducted a study examining the incidence of temperatures below multiple “frost thresholds” during the months of critical development phases for three frost-sensitive California crops: almonds, avocados and navel oranges.

The researchers found that even during the coldest winters and springs, the incidence of frost exposure declined under projected mid-21st century climate conditions by more than 50% for almonds and oranges, and by more than 75% for avocados. While farmers in 2050 will not find frost risk to completely be a worry of climates past, they will not have to contend with the same frost concerns that farmers face today.

Beyond the obvious benefits of reduced risk of crop damages, additional benefits of reduced frost exposure include lower water use and energy costs associated with mitigation actions. Irrigation is a primary means of protecting crops from frost temperatures, and with fewer hours below freezing that means fewer hours of running water and using pumps. The authors of the future frost exposure study showed that growers may collectively save tens of thousands of acre feet of water and enjoy millions of dollars in energy savings.

Few aspects of climate change are considered “positives,” and although the warming winters and springs that result in reduced frost temperatures could also come with increased pest pressure, reduced chill accumulation and other challenges, the reduction in frost exposure is a silver lining.

However, until this frost-free future arrives, growers still need to be prepared to protect their orchards from frost. To assess frost risk for the next seven days for your location, check out the new interactive Frost Advisory Tool at CalAgroClimate.org.

Avocado tasters are wrapping up a their work at UC sensory lab

A group of trained and dedicated volunteers have been tasting avocado samples at the UC Kearney Agricultural Research and Extension Center in Parlier to determine whether the GEM avocado variety can stand up to the tried-and-true Hass in grocery stores, reported Dale Yurong on ABC 30 Action News.

Yurong visited the sensory lab at Kearney where nine tasters have been meeting for months to help inform UC and USDA research that may enable commercial production of avocados in the San Joaquin Valley, an area believed to be unsuitable because of hot summers and cold winters.

The panellists identify avocado characteristics like nutty, stringy and buttery. "You're getting into the texture, you're getting into a lot of different nuances of flavor," said taster Shannon Aguilar.

GEM avocados grow on smaller trees than Hass and GEM has a tear-drop shape, while Hass is more pear-shaped. But the real test will be comparable flavor and tolerance to valley conditions.

"We believe it has a little more heat tolerance and a little more cold tolerance," said UC Cooperative Extension specialist Mary Lu Arpaia. 

The GEM may give local farmers a new crop option. One has already planted two acres of GEM.

"It's something that we probably need in this area. Something we can do and we wouldn't have to import it from other parts of the country or the world," said Marvin Flores, environmental health and safety specialist at Kearney and a member of the avocado taste panel.

UC researchers look to expand California avocado production

California avocados are the best in the world. So says downtown restaurant manager Daniel Avalos in a Valley Public Radio story by reporter Ezra David Romero.

The fact that they currently thrive only on a small swath of coastal Southern California is being challenged by UC Cooperative Extension specialist Mary Lu Arpaia. She is on a mission to find avocado varieties that withstand the hot summers and cold winters of the San Joaquin Valley, where irrigation water and crop land are more abundant and cheaper. 

She hopes to find avocado varieties that ripen at various times of year, and varieties that might be an alternative crop for citrus growers should huanglongbing, a disease that has devastated the Florida citrus crop, take hold in Central California.

"There's a void of California fruit on the market in the months of November, December and actually early January," Arpaia said. "So if we can find different selections that maybe are unique that fit into that window, then we help the entire California avocado industry."

Romero visited the UC Lindcove Research and Extension Center to see the trees in Arpaia's study. Currently, the vast majority of California avocados are the Hass variety. The goal is to breed varieties with similar eating quality that grow to a moderate height and have high yield. One potential that is already being produced by nurseries is called "gem."

"This is gem," said Eric Focht, a staff research associate in Arpaia's lab. "You can see it's a little more oval or egg shaped than Hass. It has the speckling on the skin. Now as this ripens, it will turn dark and a lot of times the speckled lenticels with get a yellow kind of golden color it it."

Another promising variety is called "lunchbox" because of its small size. According to Focht, it "just falls out of the skin." Arpaia said, "It makes wonderful guacamole and I found, with a non-replicated test in my refrigerator, the fruit doesn't brown."

Arpaia's favorite guacamole recipe is featured at the end of the story on the KVPR website.

High-density planting of avocados boosts yield

The California avocado industry is getting much-needed hope from results of a UC Agriculture and Natural Resources (UC ANR) study on high-density planting, reported Lesley McClurg on Capital Public Radio. One farmer featured in her report said, because of the drought, he is paying $1,600 per acre-foot for water, an all-time high.

Gary Bender, an advisor with UC ANR Cooperative Extension in San Diego County, believes that increasing per-acre yield will help farmers stay in business.

“We've been growing avocados wrong all these years and we're finally starting to figure it out," Bender said.

He planted trees 10 feet apart in a research trial, instead of the standard 20 feet spacing. Instead of letting the trees grow tall, the standard practice, he pruned them regularly to keep the trees short and fat.

The study was a huge success, yielding nearly 13,000 pounds of Haas avocados per acre, McClurg reported. Usually farms in the area yield between 6,000 to 7,000 pounds per acre.

 

 

Frost Hardy Avocados for Solano Micro Climates

The avocado (Persea Americana) is sometimes described as the perfect food because of its digestibility and nutritional value, according to the California Master Gardener Handbook (2002).

Our backyard has an 30 year old (as yet unidentified) avocado tree which has been a real gem!  It produces beautiful fruit and has proven to be frost hardy during a recent mid-January cold snap.  Although we live in Vallejo, which is in Sunset’s zone 17 where frosts are relatively rare, Solano County has 3 additional zones:  zones, 14, 15, and 9 in the Vacaville area.  And you could have your own micro climate within those zones.  For example a property on a hill or ridge top will have good “cold air drainage”, with temperatures a good 10-12 degrees F warmer than in lower lying areas.  

According to UC Extension San Diego, the ‘Haas’ cultivar is the preferred one for Southern California coastal valley areas, which is where most of them are grown commercially.  However, Mexican varieties (Persea americana drymifolia) can be grown in the Bay Area, as well as the “banana belts” of the San Joaquin Valley.  Top Sunset Garden Book picks include ‘Fuerte’ (hardy to 27 degrees F), ‘Bacon, ‘Mexicola’ (very cold hardy to 20 degrees F), and ‘Zutano’ (hardy to 27 degrees F).  I’m guessing our tree could be a ‘Bacon’, ‘Fuerte’ or ‘Zutano’, because the color  of our fruit is dark to medium green, turning darker when ripe.  It has a mild, nutlike flavor, and is quite good in a salad.  

Fruit ripening varies with the cultivar.  ‘Bacon’ and ‘Fuerte’ mature November to March, and ‘Mexicola’ matures August to September.  Avocado varieties have flowers categorized as Type A or Type B, depending on the time of day they open and when pollen is released.  Sunset recommends either planting a tree of each type, or buying a tree that has the opposite type grafted onto it, which is most likely the case with our tree, since we have only one.

Avocados need good drainage with occasional deep watering.  Mulch should be applied 6 to 12” deep, but it needs to be kept away from the trunk.  Although these trees are very susceptible to ‘Phytophthora’ root rot, the mulching and additional gypsum added to the soil, creates conditions which suppress this fungus.

So, experiment with this tropical treat.  Although your harvest may not be of commercial quality, some of the hardiest varieties can be successfully grown.

Photos by Bud Veliquette

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