Subtropical Fruit Crops Research & Education
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Subtropical Fruit Crops Research & Education

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Soil Mapping is Fun

WASHINGTON — USDA has re-designed its Soil Tools webpage, to now serve as a one-stop source for new, leading-edge tools and technologies to help farmers, ranchers, and other land users understand, evaluate and conserve soils.

Managed by USDA's Natural Resources Conservation Service (NRCS), the webpage offers single-site access to soil data and maps, soil databases, digital soil applications, climate data, descriptions of soils, ecological sites, statistical packages and soil-property calculators. The USDA maps and information are free with no user ID or password required.

“Along with air, sunlight and water, soil is one of the four building blocks of life on earth,” said Dave Hoover, Director of the National Soil Survey Center. “Soil is tied, in some way, to everything we use as a society. This new web portal makes it easy to find and use soils data, and provides unique, interactive tools for all customers of soils information.”

Highlights include:

  • Access to download up-to-date soil data and maps used for comparing soils over broad areas, make conservation planning and soil evaluation easier.
  • Access to Web Soil Survey and other tools that provide the ability to search for soils maps and data by location.
  • Access to soil apps that display and allow users to access data and view interactive maps.
  • "Access to calculators for soil texture and water budgeting.

The new resources are made available thanks to the joint effort of the National Cooperative Soil Survey partnership, which includes Federal and State agencies, universities, and professional societies, and exists to cooperatively investigate, inventory, document, classify, interpret, disseminate, and publish information about soils.

The California maps also have "Avocado Root Rot" breakdowns showing where plantings would be more difficult for not only avocado but also other trees sensitive to wet feet.

Attached Files
soil colors

soil colors
soil colors

Posted on Monday, October 22, 2018 at 7:58 AM

ACP Control Soon?

VISALIA – Last week's California Citrus Conference marked a major milestone for growers, and it wasn't just the 50th anniversary of the Visalia-based Citrus Research Board (CRB). It was a resounding revelation that new research may cure the greatest threat to the citrus industry in the next few years.

Michelle Heck, a molecular biologist with the USDA Agricultural Research Service, discusses her research to breed a new citrus pest that does not transmit the fatal tree disease known as huanglongbing. Photo by Michael Alvarez.

Michelle Heck, a molecular biologist with the USDA Agricultural Research Service, discusses her research to breed a new citrus pest that does not transmit the fatal tree disease known as huanglongbing. Photo by Michael Alvarez.

Michelle Heck, PhD, told the crowd of citrus growers at the Wyndham Hotel on Oct. 10 that her team might only need that much time to inbreed a generation of Asian citrus psyllids that are incapable of transmitting the deadly tree disease known as huanglongbing (HLB). The disease has already destroyed China's citrus industry, decimated Florida and Texas growing regions and is currently killing the citrus industry in Brazil.

One grower commented, “China's been dealing with this for 100 years and Brazil for 14 years. We've had this for four to five years in California and we are already knocking on the door of nailing it. That's impressive!”

Heck, a molecular biologist with the USDA Agricultural Research Service, was the first to lead a team of scientists to study the proteins involved in the interaction of the pest, plant and pathogen. One of those proteins creates a blue color in the blood of some psyllids. Her research revealed that psyllids containing the blue protein are far less efficient at transmitting HLB to the plant than others. She then bred those psyllids and took their progency and raised them on orange jasmine hedges, better known as Murraya, a plant the psyllids are attracted but is HLB resistant. The combination of the pest and plant reduced transmission of HLB to healthy citrus leaves from 32% to 2.9%.

Heck said the next steps are to continue breeding the pests that are poor transmitters of the disease to create a line of psyllids that do not transmit HLB at all. She said it would take another two years to breed an “optimized line” of the psyllid but once that was complete, that line could begin mass breeding for release.

“By sheer numbers, we can tip the scales [in the fight against HLB],” she said, “but it's unknown if these lines will out compete other psyllids [in the field].”

One grower asked if the non-transmitting line of the pest would be considered a genetically modified organism, or GMO, a distinction that could hurt fruit grown in groves with the new pest. Heck said all of the psyllids would be bred natuarally, so there is no genetic alteration of the insect itself.

“This is something the anti-GMO groups should feel good about,” Heck said.

Best Case Scenario

Victoria Hornbaker, Statewide Citrus Program Manager for the California Department of Food and Agriculture (CDFA), called the current HLB situation in California a best case scenario. She said the Citrus Pest and Disease Prevention Program's (CPDPP) No. 1 priority is to quickly detect and remove diseased trees. Shortly after the discovery of the first HLB tree in 2012, California's myriad of citrus agencies worked together to quickly implement measures to control movement of fruit and nursery stock, monitor and suppress the ACP population, and begin working on ways to detect the disease and possibly cure it.

“Instead of all commercial groves being covered by a quarantine, we said we're going to quarantine the whole state,” Hornbaker said.

By limiting the movement of citrus in and out of different quarantine zones, there is less likelihood of transporting trees from an infected area to an uninfected area. If any infected trees are discovered, they are removed, destroyed and replaced with a healthy tree. There are many early detection techniques (EDTs) being studied throughout the country, including looking for patterns in leaves, chemicals produced by trees in response to HLB, and studying molecules of the bacteria causing the disease. A recent analysis of these EDTs showed that most are about 95% effective in identifying an infected tree, and that losing 5% of healthy trees is an acceptable loss compared to devastation caused by the disease spreading unchecked.

While early detection methods of ACP are still being perfected, the fight to control the spread of the psyllid is not. After research identified the microscopic parasitic wasp radiate terminaxia as the natural enemy of the psyllid, they began working to mass produce and release them. To date, more than 11 million wasps have bee released in citrus growing regions since 2013, the closest being in Kern County.

Reproduced from Sun Gazette:

http://www.thesungazette.com/article/news/2018/10/17/pests-that-spread-citrus-disease-are-key-to-cure/

Attached Files
ACp

ACp
ACp

Posted on Friday, October 19, 2018 at 8:22 AM
  • Author: Reggie Ellis @Reggie_SGN
Tags: ACP (72), Asian Citrus Psyllid (49), citrus (274), HLB (55), huanglongbing (56)

Avocado in Southern California - 1911

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In 1911, the avocado was a relatively new crop in Southern California and the great USDA plant explorer Wilson Popenoe (pronounced POP e Noe according to Jack Shepherd), describes avocado culture and its problems

https://www.biodiversitylibrary.org/item/137628#page/31/mode/thumb

This is from the first volume ever of the Pomona Journal of Economic Botany which also has a nice description of "wither tip" of citrus in Santa Paula.

https://www.biodiversitylibrary.org/item/137628#page/5/mode/1up

 

Cover Avocado in Southern California - Wilson Popenoe
Cover Avocado in Southern California - Wilson Popenoe

Posted on Wednesday, October 17, 2018 at 5:47 AM
Tags: avocado (251), citrus (274), disease (53), horticulture (3), propagation (2)

Herbicide Injury in Avocado

Although the main objective of herbicide use in avocado orchards (and all crops) is to manage weed populations, sometimes unintentional injury of the crop itself can occur when herbicides are incorrectly applied. Herbicide injury in avocado can reduce yield, decrease fruit, reduce plant vigor, increase susceptibility to diseases and pests, and sometimes result in plant death. Common situations resulting in injury include spray drift, tank contamination, application of the wrong herbicide or rates, and herbicide carryover from a previous crop. The extent of herbicide damage on avocado can vary widely according to factors such as herbicide mechanism of action (MOA) and application rate, route of exposure, plant size and growth stage, soil properties, and weather.

Herbicide injury can be difficult to diagnose properly and is often confused with disease, insect damage, nutrient deficiencies, and other environmental stresses. It is recommended that trained researchers or Pest Control Advisers, who may utilize plant tissue, make diagnoses or soil samples along with plant symptoms, injury progression, and other plant species affected, orchard herbicide use history, weather conditions, and other factors to confirm or rule out injury from herbicides or other causes.

Where the injury occurs can also be an indication of herbicide injury. For example, if injury is on just one side of a tree or trees near another field, it may be an indication of spray drift. If it occurs only along the edge of the skirts, it may be a hint that an uneven ground spray was applied.

The majority of herbicides for use in avocado orchards in California fall into eight MOAs as defined by the Weed Science Society of America. MOAs describe the specific biological processes that are disrupted by a group of herbicides. These processes control the growth and development of plants and when interfered with, can result in plant injury or death.

Table 1: Common herbicides used in avocado, their mechanism of action, and possible injury symptoms

WSSA Group

Mechanism of Action

MOA description1

Example herbicides

Possible injury symptoms1

1

Acetyl CoA Carboxylase (ACCase) Inhibitors

Inhibits lipid creation in grasses, preventing production of plant cell membranes

Fluazifop-P-Butyl (Fusilade DX), Sethoxydim (Poast)

Chlorosis, necrotic spots, leaf crinkling, leaf distortion

3

Mitosis Inhibitors

Inhibits cell division in germinating seedlings and lateral roots

Oryzalin (Surflan)

Thickened, shortened lower stems and small, crinkled leaves

5

Photosystem II Inhibitors

Prevents the transfer of energy generated during photosynthesis, causing a buildup of reactive molecules that damage chlorophyll and cell membranes

Simazine (Princep 4L)

Chlorosis, necrosis progressing from leaf margins toward the center of the leaves, foliar applications will appear as leaf burn

9

Enolpyruvyl Shikimate-3-Phosphate (EPSP) Synthase Inhibitors

Inhibits the production of three aromatic amino acids and the enzymes and proteins built from them

Glyphosate (Roundup)

Leaves of trees and vines become chlorotic 3 to 7 days after exposure, and margins of new leaves become necrotic

12

Carotenoid Biosynthesis Inhibitors

Inhibits production of carotenoid pigments, which harvest light and protect chlorophyll from reactive molecules

Norflurazon (Solicam DF)

Plant foliage turns white and appears bleached

 

14

Protoporphyrinogen Oxidase (PPO) Inhibitors

Blocks the production of chlorophyll and causes a buildup of reactive molecules that damage existing chlorophyll, carotenoids, and cell membranes

Oxyfluorfen (Goal 2XL), Carfentrazone (Shark EW), Flumioxazin (Chateau)

Drift injury will appear as speckling on leaf tissue. The necrotic spots are sometimes surrounded by a reddish colored ring. Injury from soil applications or residues appears as a mottled chlorosis and necrosis.

21

Cellulose Inhibitors

Inhibit cell wall synthesis and plant growth

Isoxaben (Gallery 75 DF)

Chlorosis, necrosis, leaf crinkling, leaf distortion, purpling of the leaf, and stunting

22

Photosystem I Inhibitors

Disrupts photosynthesis, forming reactive molecules that destroy cell membranes

Paraquat (Gramoxone SL)

Drift injury will appear as speckling or necrotic spots on leaf tissue

1Not a complete list. Symptoms listed are likely for established orchards. For detailed descriptions of MOAs and injury symptoms, as well as a searchable database of specific injury images (e.g., “chlorosis, necrosis, stem swelling, etc.” visit http://herbicidesymptoms.ipm.ucanr.edu.

References:

Al-Khatib, K. 2015. University of California Integrated Pest Management Herbicide Symptoms. http://herbicidesymptoms.ipm.ucanr.edu (accessed 09/05/18)

Faber, B.A., C.A. Wilen, B.D. Hanson. 2016. Weeds. Pages 107-124 in University of California Integrated Pest Management Guidelines for Avocado. http://ipm.ucanr.edu/PMG/selectnewpest.avocado.html (accessed 09/05/2018)

Sosnoskie, L.M., B.D. Hanson. 2013. Understanding herbicide mechanisms (modes) of action and how they apply to resistance management in orchards and vineyards. UC Weed Science Blog Post. //ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=9383 (accessed 09/05/2018)

Weed Science Society of America. Summary of Herbicide Mechanism of Action

According to the Weed Science Society of America. https://wssa.net/wp-content/uploads/WSSA-Mechanism-of-Action.pdf (accessed 09/05/2018)

Photo: Sometimes weeds are tasty, like amaranth and purslane

organic herbicide live
organic herbicide live

Posted on Monday, October 15, 2018 at 6:51 AM
  • Author: Travis Bean
Tags: avocado (251), damage (22), herbicides (13), injury (1), weeds (28)

Good Fungi, Healthy Roots

There's lots of talk about good soil fungus and bad fungus and what might be done about improving good ones.  It's hard to figure out what is talk and what is actually happening.  Robert Kourik can help make clear some of the dirt around the roots.

There are amazing beneficial fungi that promote the healthiest roots of California native and agricultural plants. Nearly all plants, especially trees, need this symbiotic relationship for superior growth. Almost all California perennials, native trees and shrubs form this mutally-beneficial relationship. This lecture will explain what the relationship is (called mycorrhizal association), where in the roots it happens, how to promote it, how it increases yields and whether or not purchased inoculants are needed. The roots of native plants, landscaping plants, and fruiting trees will be covered.

If you got time, stop in and hear the talk.

 

kourik talk
kourik talk

avocado roots and dirt
avocado roots and dirt

Posted on Friday, October 12, 2018 at 7:26 AM

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