Posts Tagged: avocados
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.
Dedicated growers and research support from the University of California have made avocados a California success story. As part of the UC Global Food Initiative, which is channeling UC resources toward sustainably feeding the world's growing population, the California avocado experience can help alleviate food insecurity and poverty overseas.
Two UC Cooperative Extension specialists found a way to do that in Tanzania, Africa, where 69 percent of the population live below the poverty line and 16 percent of children under 5 are malnourished. In March 2017, UCCE biocontrol specialist Mark Hoddle and UCCE subtropical crops specialist Mary Lu Arpaia traveled to the east African nation to help growers there with their fledgling avocado industry.
In the late 19th Century, German missionaries introduced avocados to Tanzania when it was colonized by this European nation. Germany lost influence over the African country following World War I, but huge non-commercial avocado trees still thrive in the landscape.
Recently, attempts at commercial production growing the popular Hass variety are gaining momentum.
With proximity to a European market hungry for fresh avocados, Rungwe Avocado Company planted 250 acres of the Hass variety in the southern highlands around Mbeya near Lake Malawi, which establishes the border of south western Tanzania with Zambia and Malawi. In order to grow production to a level that would make the export to Europe practical and to support rural residents with a viable business option, approximately 3,700 small landholder farmers, known as outgrowers, were recruited to grow avocados. They manage small plots with as few as 20 trees to larger acreage with more than 200 trees, with participating farms ranging in elevation from 1,200 to nearly 6,000 feet.
However, this fledgling industry is experiencing production challenges, prompting the company to contact UC Cooperative Extension. UC faculty, specialists and advisors have conducted research on Hass avocados for decades in California and worked closely with growers to extend information that has supported the development of an industry with high-yielding trees producing premium fruit valued at more than $400 million per year.
“One of the aims of the Global Food Initiative is to deploy UC's best research and extension practices to address the key challenge of improving food production,” Arpaia said. “That's why we went to Tanzania.”
Hoddle and Arpaia visited growers, extension technicians, packing house managers and logistics experts. They identified production, pest management and fruit handling challenges faced by the avocado industry.
“The situation in Tanzania is quite different than California, and also different compared to Central and South America, where we have also worked on avocado production issues,” Hoddle said. “But we identified familiar issues that affect management for which there are solutions.”
Hoddle examined the Tanzanian avocado trees and fruit, and collected insect specimens. He said the insect damage was minimal at the time of the week long visit.
“That surprised me because of the insect biodiversity in Africa,” he said. “There was little evidence of heavy leaf feeding. There was some evidence of fruit damage caused by insect feeding on the skin, but they don't seem to have fruit boring weevils or caterpillars that we commonly see in parts of Mexico, Central and South America.”
A critical issue is extending entomological information to the outlying farmers to improve their ability to identify and manage beneficial insects and crop pests.
“They don't have the magnifying loops, collecting vials and insect boxes that we regularly use for insect identification,” Hoddle said. “I showed them my Leatherman tool, which can be used to open up fruit and look for damage. They need these basic tools.”
A post-harvest expert, Arpaia was able to identify ways to improve picking, handling, storage and shipping practices that would result in top quality fruit arrival in Europe.
The two scientists produced a report, which emphasized the need to provide outlying growers with basic equipment and agronomic information.
“We want to help them be better avocado farmers so the crop can be a greater contributor to the country's economy,” Arpaia said. “Boosting this industry will also give people all over Tanzania the opportunity to add nutritious avocados to their diets.”
Mary Lu Arpaia, a Cooperative Extension subtropical horticulturalist with UC Agriculture and Natural Resources (UC ANR) and the Department of Botany and Plant Sciences at UC Riverside, hosts an avocado tasting each month on the UCR campus. Attended typically by about 60 people, the tastings have grown in popularity over the years.
Eric Focht, a staff research associate in the Arpaia lab, helps organize the tastings; the guacamole he prepares specially for the occasion serves as an additional attraction. Focht has been working on avocados since 1999, the year he joined UCR as a staff member. His relationship with the campus, however, began before then; his father, now retired, was a professor on campus.
Typically, participants of the avocado tastings sample six avocados which come from UC ANR's South Coast Research and Extension Center in Irvine. “Hass control fruit are purchased from or donated by a packing house,” Focht says.
First, participants do a visual assessment of the fruit, evaluating texture, size and color. Next they step into a room where they do the blind tastings.
“The data is compiled and used to assess, among other things, which of our new breeding selections shows promise and should be pushed for eventual release,” says Focht, whose duties include coordinating field activities, designing field layouts, generating maps and databases, selecting avocado varieties of interest, interacting with growers and the public, troubleshooting, and directing the day-to-day operations of the lab when Arpaia is away.
“Right now our 465518-99 has been performing very well,” he says, “but in former years, its peak season is February through April. In the fall, Reed is always a good fruit with good flavor and texture. I prefer a fruit that peels easily and has good flavor. If it doesn't peel clean from the skin, I tend to overlook it for something else with good flavor and convenient packaging.”
The avocado growing season varies from variety to variety. By planting out several varieties, it is possible to have avocados year round in one's garden. Focht explains that the growing season varies regionally as well.
“The season in San Luis Obispo is months later than it is in San Diego,” he says.
Most avocado acreage in California is currently in Northern San Diego County. Most avocado acreage in the U.S. is in California. Other states with avocado industries include Florida and Texas. Worldwide, avocados are grown in Mexico, Chile, Peru, Israel, Australia, South Africa and New Zealand.
“An acre of avocado trees typically requires 2.5-4 acre-feet of water per year depending on weather and other factors,” he says. “The drought is resulting in lost acreage as farmers can either not afford or not find enough water for their trees. Successful farmers are having to modify their cultural practices to stay competitive.”
The next avocado tasting at UCR will be Aug. 12, 2015. For more information about the tastings, contact Focht.
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.
Mary Lu Arpaia is conducting research to change that.
Avocados are native of semi subtropical high elevation rainforests in Mexico and Central America. A delicious and highly nutritious fruit, the cultivation of avocado has spread around the world. In California, growers are having commercial success in areas with year-round mild climates, such as San Diego and Ventura counties.
Though avocados are frost sensitive to be sure, it is not the cold winter climate that is the greatest impediment to avocado production in the state's inland valleys. It's the heat.
“Plant leaves have stomata, small openings that allow water vapor to move out of the plant to cool the leaf surface,” Arpaia said. “It works something like perspiration on people. Moisture exits the pores and cools the skin.”
The stomata on the leaves of Hass avocados – the variety most favored by California consumers – close when the temperature rises above 90 degrees. No moisture is released from the closed stomata and the plant overheats, causing fruit drop.
“To grow avocados in the valley, we need to have a variety that can tolerate heat better than Hass,” Arpaia said.
“The ones that we're testing in the field have eating quality comparable to Hass,” Arpaia said.
Lindcove is situated where the valley floor is gently rising toward the Sierra Nevada. The slope allows cold air to slip down to lower elevations, giving farmers in the area an advantage of a few degrees in the winter. The geography has made the area an important location for citrus production. But heat-tolerant avocados could be an alternative.
East-side citrus farmers may be looking for other options if Huanglongbing (HLB) disease makes its way to the area. Already, the pest that spreads HLB, Asian citrus psyllid, is established in some parts of the valley and spreading. Once a tree is infected with HLB, it cannot be cured.
“Growers have made good money on avocados,” Arpaia said. “In the San Joaquin Valley, water is relatively cheap and we have better water quality than San Diego County. There are good, well-drained soils. Avocados' frost sensitivity is similar to lemons. If farmers have property where they can grow lemons, they could try avocados.”
An initiative to enhance competitive and sustainable food systems is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.