Posts Tagged: avocado
Avocado growers have been ecstatic at fruit prices and are walking their groves more avidly, checking things out and seeing lots of things they don't normally see. A recent grower find has been a blob of Fulgio septica - ‘Dog Vomit' or ‘Dog Fungus'. It's not vomit, it's not a fungus, but a slime mold that lives off the organic matter littering orchards and in mulched gardens. After the rains and when it starts to warm up, the spores of these non-animal, non-plants germinate and start moving around. They aggregate into a mass, called a plasmodium, a super individual that starts out as a yellowish, spongy mass that can move in a slow, amoeboid-like fashion. It gradually hardens and can take on the brownish-tan coloring seen in the image below. As it dries, it breaks up and blows away. It won't do harm to living plants, simply feeding on dead material. It will gradually disappear. So, as you walk your orchard or your backyard, enjoy the unusual appearance of a rainy year member of the web of nature.
providing some advantage to the farmer. Frequently, these are new fertilizer mixes presented as proprietary cocktails promoted and dispensed with promises of a multitude of profitable (yet improbable) benefits to the buyer. With the large number of new products available, and the number of salespeople promoting them, it is often difficult for growers to distinguish between products likely to provide real benefit, and those that may actually reduce the profitability of the farm.
In all situations when a company approaches the University or a commodity research board with a new product or technology for sale to California growers, these institutions act as grower advocates. They are charged with sorting through the available information; asking the right questions; getting the necessary research done if the available information warrants this pursuit; disseminating accurate information on these new technologies and products, and doing all that can help maximize grower profits now and in the future. When approached with a new product or technology it is obligatory to challenge claims with the following questions:
Is there some basic established and accepted scientific foundation on which the product claims are made?
Language that invokes some proprietary ingredients or mysterious formulations, particularly in fertilizers mixes registered in the State of California, raises red flags. A wide range of completely unrelated product benefit claims (such as water savings, pesticide savings, increased earlier yield) raises more red flags. Product claims that fall well outside of any accepted scientific convention generally mean the product is truly a miracle, or these claims are borderline false to entirely fraudulent.
Has the product undergone thorough scientific testing in orchards?
Frequently, products are promoted based on testimonials of other growers. While testimonials may be given in good faith, they are most often not backed up by any real scientific testing where a good control was used to compare orchard returns with and without the product.
A “test” where a whole block was treated with a product and which has no reliable untreated control does not meet accepted standards for conducting agricultural experiments. Also, a treated orchard cannot reliably be compared to a neighboring untreated orchard; and a treated orchard cannot be compared to the same orchard that was untreated the previous crop year. Even a test with half a block of treated trees and half untreated is not considered dependable by any known scientific standard of testing.
Only a well designed, statistically replicated, multi-year trial allows for direct comparison of untreated versus treated trees with statistical confidence. Verifiable data from tests that meet acceptable standards of scientific design, along with access to raw baseline (before treatment) yield data from the same trees (preferably for the two years prior) should be used to determine the validity of test results provided.
Are the test results from a reliable source?
If the testing were not done by a neutral party, such as university scientists, agency, or a reputable contract research company using standard scientific protocols, this raises red flags. If the persons overseeing the tests have a financial interest in seeing positive results from the product, it raises red flags.
Does the product have beneficial effects on several unrelated farm practices?
A product that increases production of trees, makes fruit bigger, reduces pests, reduces water use, and reduces fertilizer costs, is more than a little suspicious. In reality, if such a product really existed, it would not need any testing at all because its benefits would be so obviously realized by the grower community that it would spread rapidly by word of mouth and embraced by the entire grower community.
Are other standard and proven farm products put down in the new product sales delivery?
If a new product vendor claims that their product is taken up 15 times faster than the one growers are currently using, or is 30 times more efficient, it probably costs 15 to 30 times more per unit of active ingredient than the standard market price. Growers should always examine the chemical product label to see what active ingredient they are buying. There has to be a very good reason to pay more for an ingredient where previously there had been no problem supplying the same ingredient at a cheaper price to trees in the past.
There are impartial sources of such information available to farmers to help corroborate information provided by product vendors. Perhaps the most reliable and accessible impartial research and education resources for growers are their local Cooperative Extension Farm Advisors and commodity research boards.
When promising products emerge, local university Farm Advisors can advise growers on how to evaluate these products and may help design a small trial to test a particular product on a few trees under local orchard conditions. If in these pursuits a truly promising new product or technology emerges, research board funding may follow but only on the recommendation of that board's Research Committee.
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. And there is more on this story at:
Mary Lu Arpaia
Old crop, new crop. What's up there in the trees? Are they big enough to sell? Is there a good set for next year? These are questions every avocado grower has every year, and often all year long. What is up there in the trees is confounded by what is called the "Avocado Illusion".
In a Science Magazine Letters to the Editor in Dec 1990, Paul Sandorff commented on a book written by Maurice Hershenson called The Moon Illusion. In the book Hershenson described the illusion of why the moon seemed so much larger when it was on the horizon than when it rose to its zenith on the same night.
Sandorff said that this illusion applied to avocados since it was so hard to gauge the size of avocados when they were in the tops of the tree canopy. It is the surrounding environment that puts a context to size according to this theory of illusion.
Hershenson added to this observation in the March 1991 Science letters section with the comment that the leaves surrounding the fruit changes our depth perception and so changes our idea of the fruit size.
A further addendum to the avocado illusion theory is that since the fruit are the same color as the leaves (they are both dark green and the fruit unlike most other fruit continues to photosynthesize), it is hard to actually make out the fruit. You can be looking right at the fruit and not see it, confusing it with a leaf.
This illusion makes for difficult fruit estimation. To compensate for this illusion, I will eye the canopy in quadrants, counting the number of fruit, then arbitrarily doubling that total number. It usually gives a pretty close number to the real number of fruit that are in the tree.
Can you count the number of fruit in this canopy?
'Pixie' mandarin is a very vigorous, upright tree. Although the fruit is small, hence its name, it can produce fruit on the ends of long branches which deform the canopy structure, making it hard to pick. The sweet, seedless fruit is worth picking, though. The rootstock standards for this small industry are ‘Citrumelo' and ‘C-35' citrange. The industry is looking for alternatives to these choices, especially those that reduce the vigor of the trees.
There is no one ideal rootstock at this point and growers have the option of a wide range of choices. The search includes those that are resistant to Citrus Tristeza Virus (CTV), Phytophthora, calcareous soils and ideally one that is resistant to the bacteria that causes Huanglongbing.
In many California coastal growing areas, land is expensive, water scarce and costly and prone to calcareous soils that are derived from marine sediments which can bring on iron chlorosis. Growers are also looking for smaller trees that will give early economic returns, are easier to prune and pick, and may be more compatible with the economics driven by Huanglongbing.
‘Citrumelo' citrange yields a large tree with good quality and quantity of fruit. It is tolerant of CTV (Citrus tristeza virus) and Phytophthora spp, but is susceptible to iron chlorosis in high pH soils. ‘C-35' citrange is a smaller tree than Citrumelo, also has resistance to Phytophthora spp and CTV, and is more tolerant of high pH soils.
The USDA had a breeding program in California which was taken over by the University of California. Out of this breeding project, the university selected three rootstocks for release in 2009 because of their horticultural characteristics, such as dwarfing, although not as much as ‘Flying Dragon' trifoliate, resistance to CTV and tolerance of calcareous soils. These three rootstocks also show good tolerance to Phytophthora parasitica and nematodes.
Pixie growers have been looking for a more compact tree, easier to handle and not need so much pruning. They funded a long-term project to see how these newer selections of rootstock performed in their area which has a hot summer/cool winter. A 2014 planting of ‘Pixie' has been evaluating the size reducing effects of the relatively new rootstocks ‘Bitters' citrange, ‘Carpenter' citrange and ‘Furr' citrange. After two years, ‘Pixie' on ‘Citrumelo' is the largest tree. Of the new rootstocks, ‘Furr' is the largest and ‘Bitters' the smallest. The trial was replicated at two sites with two different pH soils. At one site with the highest soil pH, ‘Bitters' showed iron chlorosis.
Photo: long whip growth on 'Pixie'