What a great find and it was there all along, just like a used book store can be a gold mine at times.
This is the section of Subtropical Fruit Pests by Walter Ebeling that covers avocado pests in not only California, but what was and is known to exist in other avocado growing regions around the US and the world. It was reproduced at the Hoshi Foundation's Avocadosource website. At this point it only contains the chapters pertaining to avocado. Other chapters in the full text cover citrus, grape, walnut, almond pecan, olive, fig, date and other "Minor Subtropical Fruits". The beauty of the book is not only historical, but that it is still current (although the DDT recommendations are out of date) for many pests. It also chronicles pests that have appeared in the past, disappeared and then reappeared. An example is Avocado Bud Mite - here, gone, here and seemingly gone again, probably to reappear sometime in the future. This is no replacement for the UC-IPM website, http://ipm.ucanr.edu/PMG/crops-agriculture.html , but it is a good look at how the pest has been managed in the past and is done so currently.
I thought I had the only copy of this book in Ventura County, but you could too. There are some listed on ABE Books for cheap.
This pestiferous book was compiled by Walter Ebeling at UC Riverside/Los Angeles. He was of some note, considered the Father of Urban Entomology. As you can see from the descriptions of avocado pests, he was a good all round entomologist, as well. Urban entomology really forces you to know a lot because of the diversity of arthropods in urban settings. He passed in 2010 and was recognized world-wide for his work.
Professor Emeritus of Entomology
November 26, 1907 – December 17, 2010
Walter Ebeling, world-renowned entomologist and pioneer in the field of Urban Entomology, died 17 December 2010 in a care facility in Bandon, Oregon at the age of 103. "Professor Ebeling was a legendary research entomologist," said Dr. Michael Rust, Professor of Entomology at the University of California, Riverside, who replaced Dr. Ebeling upon his retirement in 1975. "He had tremendous abilities, tireless energy, and a passion for science. He was an expert in so many fields of entomology including agriculture, physiology, and insect behavior. Dr. Ebeling helped develop Urban Entomology into a respected independent area of research."
Read more of his Memoriam: http://senate.ucr.edu/agenda/120221/IN%20MEMORIAM-Walter%20Ebeling.pdf
Carbonateceous? Gypsum? Read on.
Soil pH or the “acidity” or lack of acidity of a soil can be confused by the different uses and chemistries that surround the term pH, or the power of hydrogen. This can be further confused by the terms “alkalinity” or “basicity” of the soil or the soil solution which can further confuse the situation by whether the solid or liquid phase of the soil is being measured. So, in short, a soil is acid if it has a pH below 7 (more hydrogen ions) and basic when above 7 (fewer hydrogen ions). Big numbers are more basic, small numbers more acidic.
The natural world has a pH scale of 1 to 14. Knowing soil pH is important because it can tell you the inherent fertility of a soil. Usually the higher the number between 5 and 8, the more “basic” nutrients are present, like calcium, magnesium and potassium. When the numbers get lower than 5 and larger than 8, the nutrients may not be there or they may be tied up. Changing the pH can often release nutrients that are not available. Iron and zinc plant deficiencies are most often controlled by soil pH and once pH is neutralized or made acid, the deficiency disappears. In a way, pH is one of the most important nutrient indicators of a soil's fertility and managing should be an essential practice.
Soils that have an elevated pH, those above 7, are usually dominated by carbonate and most commonly this is calcium carbonate. As a rock, we call this limestone which is derived from sea shells or coral. As a mineral, it is called calcite. And in various manipulated forms it is called,calx, lime, calcium hydroxide, calcium oxide,calcined lime, quicklime. Maybe other names, as well, depending on how it is made and used. Mixed with quartz sand it is made into glass. When an acid is added to calcium carbonate, like citric acid, sulfuric acid or rain water (yes pure rain water is acidic), the reaction gives off carbon dioxide and water. (When you respire, burning sugar which is a form of carbonate, you do the same thing, giving off CO2and H2O). When calcium oxide or lime is mixed with water and left to harden, it forms cement when it absorbs carbon dioxide from the air. So, lime, limestone and calcium carbonate are not very soluble. But it does dissolve. Calcium carbonate is a salt and dissociates into calcium ions and when surrounded by water molecules, the carbonate becomes bicarbonate ions. When the water dries up, the bicarbonate becomes carbonate again. A soils report may refer to this cement as “free” or “diffuse lime”, indicating that there is a lot present, and it may even be possible to see the old shells there.
A soil that is dominated by calcium carbonate is called a calcareous soil. It is the carbonate that defines the soil, it has an elevated pH, usually between 7.5 and 8, depending on other minerals in the soil (minerals are naturally occurring chemicals). A high pH leads to plant nutrition problems. It's not until the soil is acidified to drive off the carbonate as carbon dioxide that the pH will drop and the nutrient deficiency disappears.
One of the problems with the word “calcareous” is that it can be interpreted as meaning dominated by calcium. A soil or water analysis may reveal high levels of calcium and this can lead to concern. Calcium is a base cation, necessary for plant and human growth. In western states, water and soil tend to have calcium as the dominant cation, balancing anions like sulfate and carbonate and in some cases chloride. The important character to look for, though, is the carbonate or bicarbonate in the soil or water. It's not the calcium that is controlling pH, it's the carbonate. Very commonly calcium is said “to reduce the acidity of soil.” But it's not the calcium, it's the carbonate.
So, does this seem like a big semantic problem, how many dancing on the head of the pin sort of debate? No, because one of the most common recommendations for correcting an alkaline water/soil is to add gypsum – calcium sulfate. In a calcareous soil, calcium is already present, so adding more calcium is not going to change it, but rather increase it. Sulfate does not displace carbonate. Carbonate just stays there because calcium carbonate is not very soluble. Remember it is cement. Actually, adding gypsum is adding more salt which has its own problems - leading to saline soils.
So, this blog all came about because two different people asked me about correcting iron deficient avocado trees in calcareous soils (or a carbonateceous soil as I call it), with gypsum. pH correction is not going to occur with gypsum. An acid needs to be added to drive the carbonate off as carbon monoxide and then the pH comes down. So, you use acids or elemental sulfur that converts to sulfuric acid or urea-sulfuric acid fertilizer, or long-term use of acid fertilizers like ammonium sulfate or organic mulches that gradually create acid conditions.
Soil acidification as a practice is a separate subject all together that needs to be discussed, but gypsum is not normally a part of the process of field acidification. Does that mean gypsum does not have a place in soil management? It does, just not in the case of calcareous soils. And even though you can see bags of lime and dolomite (calcium-magnesium carbonate) on store shelves, for sure don't use that in the calcareous soils of California.
So, what about gypsum and sodic soils – soils dominated by sodium. And what about serpentine soils – soils dominated by magnesium? There is more to tell about gypsum.
Photo: old shells in the soil
- Author: Karey Windbiel-Rojas
The California Department of Food and Agriculture (CDFA) and the United States Department of Agriculture (USDA) have confirmed the detection of the citrus disease known as Huanglongbing (HLB), or citrus greening, in Riverside County. The disease was detected in plant material taken from a grapefruit tree in a residential neighborhood in the city of Riverside near I-215.
The infected tree has been removed and agriculture officials are moving swiftly on mandatory surveying in an 800-meter area. Mandatory treatments will soon follow. CDFA staff will visit all regulated entities in the quarantine area, including retail and production nurseries and packinghouses. Additionally, local, state and federal agriculture authorities are working together to determine potential implications to the University of California, Riverside, which will fall within the 5-mile quarantine area.
Riverside County Agricultural Commissioner/Sealer Ruben Arroyo plans to take an aggressive stance on any abandoned groves in the area, and the Citrus Pest & Disease Prevention Program outreach team is already working with the City of Riverside to inform residents of the actions needed to stop HLB's spread.
Please read the full press release shared on July 25 by Riverside County.
For more information about ACP or HLB, Riverside County residents may call the Agricultural Commissioner's Office at (951) 955-3045 or CDFA's toll-free pest hotline at 1-800-491-1899 or visit: www.cdfa.ca.gov/plant/acp//span>
- Author: Jeannette Warnert
California citrus farmers have their ears perked for all news related to Asian citrus psyllid (ACP) and huanglongbing (HLB) disease, but the very latest advances have been available only in highly technical research journals, often by subscription only.
UC Cooperative Extension scientists are now translating the high science into readable summaries and posting them on a new website called Science for Citrus Health to inform farmers, the media and interested members of the public.
“The future of the California citrus depends on scientists finding a solution to this pest and disease before they destroy the industry,” said Beth Grafton-Cardwell, UC Cooperative Extension citrus entomology specialist. “Our farmers want to stay on top of all the efforts to stop this threat.”
Grafton-Cardwell and UC Cooperative Extension biotechnology specialist Peggy Lemaux are the two scientists behind the new website. When scientists make progress toward their goals, Grafton-Cardwell and Lemaux craft one-page summaries with graphics and pictures to provide readers with the basics.
For example, the website outlines scientific endeavors aimed at stopping the spread of huanglongbing disease by eliminating the psyllid's ability to transfer the bacterial infection. This section is titled NuPsyllid, and contains summaries of three research papers including one by UC Davis plant pathologist Bryce Falk.
Falk is collecting viruses found in Asian citrus psyllid; so far he has identified five. He is looking into the potential to utilize one of the viruses as is or modify one of the viruses to block the psyllid's ability to transmit the bacterium. For example, the virus might out compete the bacterium in the psyllid's body.
Another focus of the website is HLB early detection techniques (EDTs). If HLB-infected trees are found and destroyed before they show symptoms, ACP is less likely to spread the disease to other trees. EDT research described on the website includes efforts to detect subtle changes in the tree that take place soon after infection, such as alterations in the scents that waft from the tree (studied by UC Davis engineer Cristina Davis), changes in the proteins in the tree (studied by UC Davis food scientist Carolyn Slupsky) and starch accumulation in the leaves (studied by UC farm advisor Ali Pourreza).
As more research is published, more one-page descriptions will be added to the website. The website contains a feedback form to comment on the science and the summaries.
Photo: ACP traps
So where is the highest potential for avocado root rot in California? It turns out that the Natural Resource Conservation Service has taken the soils maps that have been generated for use by growers, engineers, planners and others over the years and used the data to rate soils for their sensitivity to root rot conditions. In many cases the county-based maps have been updated with new information, as well. It is now much easier to see where root rot would be more likely. The two major soil characteristics of soil texture and depth and how they affect drainage are the major parameters used to assess the root rot hazard. The soil surveys for years were only available in printed form, and then became available online about 2005. Just recently the added feature of identifying “root rot” soils was created. Now at the touch of a button, maps of where these soils are found are available. It looks like all California counties can be viewed from an avocado root rot hazard, even though avocados may not be grown in that climate, like Humboldt, but who really knows what can grow there. Soils that are conducive to Phytophthora root rot for avocados, would also be conducive for root rot in other plants species, as well. So, this information is helpful for identifying where rhododendrons or other susceptible species might have problems, as well.
Of course, this is just the first step in assessing the potential for root rot. Irrigation management is critical for creating root rot conditions that can occur even in soils that are not conducive to the disease. So, a soil identified as having a higher potential for root rot does not mean you cannot plant an avocado in it. The key is water management and how the tree is planted and how that soil is managed.
So, go to the Web Soil Survey: https://websoilsurvey.sc.egov.usda.gov/App/HomePage.htm
Click on an Area of Interest (type in California and your county or even your address)
Then click on “Soil Map” tab and you will see the map polygons or soil units for that area
Then click on “Soil Data Explorer” tab to get “Suitabilities and Limitations Ratings” on the left side
Click on “Land Management” and there is “Avocado Root Rot Hazard”
Click on “View Rating” and the map will appear with colored units showing root rot hazard along with a chart showing the root rot hazard of the different soils in the map.
Wow. Watch out for those dark areas.