- Author: Ben Faber
This note from Cressida Silvers, either go to Temecula or maybe do a more local version of the training:
Good afternoon,
The upcoming CAPCA meeting (see below for details) in Temecula is a 2-day event (12 CEUs), including a workshop and field visit focused on detecting live ACP in citrus trees, and using monitoring strategies to evaluate ACP presence in orchards.
If there is enough interest locally (SLO, Santa Barbara, Ventura), we could put on a similar workshop/field training for ACP monitoring for anyone interested. Let me know if that would be helpful, and how far you would be willing to travel for that.
Thanks,
Cressida
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Cressida Silvers
ACP/HLB Grower Liaison
Ventura, Santa Barbara and San Luis Obispo Counties
805 284-3310
CAPCA Spring Summit Focuses on
Asian Citrus Psyllid:
April 24 – 25
The California Association of Pest Control Advisers (CAPCA) will host its 2018 Spring Summit on April 24 – 25 in Temecula. Summit attendees will tour UC Riverside's citrus grove and experiment station, and will learn about Asian citrus psyllid mitigation standards for bulk citrus movement, scouting techniques, identification and management strategies.
With more than 500 HLB-positive trees confirmed in Southern California, it is critical that pest control advisers involved with citrus stay up to date with ACP detection and management strategies. The Spring Summit will include the following topics and speakers:
- Strategies for management of Asian citrus psyllid in California – Dr. Beth Grafton-Cardwell, University of California Division of Agriculture and Natural Resources
- Mitigation standards for the new Asian citrus psyllid regional quarantine – Victoria Hornbaker, California Department of Food and Agriculture
- Scouting techniques and identification of Asian citrus psyllid in the field – Alan Washburn, Citrus Pest & Disease Prevention Program
- Update on Asian citrus psyllid and HLB management – Bob Atkins, Citrus Pest & Disease Prevention Program
The event is accredited for 12 hours (2.50 Laws and 9.50 Other) of continuing education units by the Department of Pesticide Regulation, as well as 11.50 California Crop Advisers hours. To view the full program schedule, click here.
To register for the CAPCA Spring Summit, click here.
- Author: Ben Faber
Like most of us, trees don't want to be eaten alive.
To prevent this gruesome fate, they developed extremely tough cell walls around 400 million years ago. For millions of years, nothing could break down lignin, the strongest substance in those cell walls. When a tree died, it just sank into the swamp where it grew. When the fossil record started showing trees breaking down around 300 million years ago, most scientists assumed it was because the ubiquitous swamps of the time were drying up.
But biologist David Hibbett at Clark University suspected that wasn't the whole story. An alternative theory from researcher Jennifer Robinson intrigued him. She theorized that instead of ecosystem change alone, something else played a major role - something evolving the ability to break down lignin. Through evolutionary biology research supported by the Department of Energy's (DOE) Office of Science, Hibbett and his team confirmed her theory. They found that, just as she predicted, a group of fungi known as "white rot fungi" evolved the ability to break down lignin approximately the same time that coal formation drastically decreased. His research illustrated just how essential white rot fungi were to Earth's evolution.
Fungi are still indispensable. The short-order cooks of the natural world, they have an unheralded job making nutrients accessible to the rest of us. Just like cooking spinach makes it easier to digest, some fungi can break down plant cell walls, including lignin. That makes it easier for other organisms to use the carbon that is in those cell walls.
"We all live in the digestive tract of fungi," said Scott Baker, a biologist at DOE's Pacific Northwest National Laboratory. If we weren't surrounded by fungi that decay dead plant material, it would be much harder for plants to obtain the nutrients they need.
To understand fungi's role in the ecosystem and support biofuels research, scientists supported by DOE's Office of Science are studying how fungi have evolved to decompose wood and other plants.
The Special Skills of Fungi
Fungi face a tough task. Trees' cell walls contain lignin, which holds up trees and helps them resist rotting. Without lignin, California redwoods and Amazonian kapoks wouldn't be able to soar hundreds of feet into the air. Trees' cell walls also include cellulose, a similar compound that is more easily digested but still difficult to break down into simple sugars.
By co-evolving with trees, fungi managed to get around those defenses. Fungi are the only major organism that can break down or significantly modify lignin. They're also much better at breaking down cellulose than most other organisms.
In fact, fungi are even better at it than people and the machines we've developed. The bioenergy industry can't yet efficiently and affordably break down lignin, which is needed to transform non-food plants such as poplar trees into biofuels. Most current industrial processes burn the lignin or treat it with expensive and inefficient chemicals. Learning how fungi break down lignin and cellulose could make these processes more affordable and sustainable.
Tracing the Fungal Family Tree
While fungi live almost everywhere on Earth, advances in genetic and protein analysis now allow us to see how these short-order cooks work in their kitchen. Scientists can sample a fungus in the wild and analyze its genetic makeup in the laboratory.
By comparing genes in different types of fungi and how those fungi are evolutionarily related to each other, scientists can trace which genes fungi have gained or lost over time. They can also examine which genes an individual fungus has turned "on" or "off" at any one time.
By identifying a fungus's genes and the proteins it produces, scientists can match up which genes code for which proteins. A number of projects seeking to do this tap the resources of the Joint Genome Institute (JGI) and the Environmental Molecular Sciences Laboratory (EMSL), both Office of Science user facilities.
Understanding the Rot
Just as different chefs use different techniques, fungi have a variety of ways to break down lignin, cellulose, and other parts of wood's cell walls.
White Rot
Although fungi appeared millions of years earlier, the group of fungi known as white rot was the first type to break down lignin. That group is still a major player, leaving wood flaky and bleached-looking in the forest.
"White rot is amazing," said Hibbett.
To break down lignin, white rot fungi use strong enzymes, proteins that speed up chemical reactions. These enzymes split many of lignin's chemical bonds, turning it into simple sugars and releasing carbon dioxide into the air. White rot is still better at rending lignin than any other type of fungus.
Brown Rot
Compared to white rot's powerful effects, the scientific community long thought the group known as brown rot fungi was weak. That's because brown rot fungi can't fully break down lignin.
Recalling his college classes in the 1980s, Barry Goodell, a professor at the University of Massachusetts Amherst said, "Teachers at the time considered them these poor little things that were primitive."
Never underestimate a fungus. Even though brown rot fungi make up only 6 percent of the species that break down wood, they decompose 80 percent of the world's pine and other conifers. As scientists working with JGI in 2009 discovered, brown rot wasn't primitive compared to white rot. In fact, brown rot actually evolved from early white rot fungi. As the brown rot species evolved, they actually lost genes that code for lignin-destroying enzymes.
Like good cooks adjusting to a new kitchen, evolution led brown rot fungi to find a better way. Instead of unleashing the brute force of energy-intensive enzymes alone, they supplemented that enzyme action with the more efficient "chelator-mediated Fenton reaction" (CMF) process. This process breaks down wood cell walls by producing hydrogen peroxide and other chemicals. These chemicals react with iron naturally in the environment to break down the wood. Instead of fully breaking down the lignin, this process modifies it just enough for the fungus to reach the other chemicals in the cell wall.
There was just one problem with this discovery. In theory, the CMF chemical reaction is so strong it should break down both the fungus and the enzymes it relies on. "It would end up obliterating itself," said Jonathan Schilling, an associate professor at the University of Minnesota.
Scientists' main theory was that the fungus created a physical barrier between the reaction and the enzymes. To test that idea, Schilling and his team grew a brown rot fungus on very thin pieces of wood. As they watched the fungus work its way through the wood, they saw that the fungus was breaking up the process not in space, but in time. First, it expressed genes to produce the corrosive reaction. Two days later, it expressed genes to create enzymes. Considering fungi can take years or even decades to break down a log, 48 hours is a blip in time.
Scientists are still trying to figure out how much of a role the CMF process plays. Schilling and like-minded researchers think enzymes are still a major part of the process, while Goodell's research suggests that CMF reactions do most of the work. Goodell's team reported that CMF reactions could liquefy as much as 75 percent of a piece of pine wood.
Either way, the CMF process offers a great deal of potential for biorefineries. Using brown rot fungi's pretreatment could allow industry to use fewer expensive, energy-intensive enzymes.
A Close Collaboration
Not all fungi stand alone. Many types live in symbiosis with animals, as the fungus and animal rely on each other for essential services.
Partnerships with Rumens
Cows and other animals that eat grass depend on gut fungi and other microorganisms to help break down lignin, cellulose, and other materials in wood's cell walls. While fungi only make up 8 percent of the gut microbes, they break down 50 percent of the biomass.
To figure out which enzymes the gut fungi produce, Michelle O'Malley and her team at the University of California, Santa Barbara grew several species of gut fungi on lignocellulose . They then fed them simple sugars. As the fungi "ate" the simple sugars, they stopped the hard work of breaking down the cell walls, like opting for take-out rather than cooking at home.
Depending on the food source, fungi "turned off" certain genes and shifted which enzymes they were producing. Scientists found that these fungi produced hundreds more enzymes than fungi used in industry can. They also discovered that the enzymes worked together to be even more effective than industrial processes currently are.
"That was a huge diversity in enzymes that we had never seen," said O'Malley.
O'Malley's recent research shows that industry may be able to produce biofuels even more effectively by connecting groups of enzymes like those produced by gut fungi .
Termites as Fungus Farmers
Some fungi work outside the guts of animals, like those that partner with termites. Tropical termites are far more effective at breaking down wood than animals that eat grass or leaves, both of which are far easier to digest. Young termites first mix fungal spores with the wood in their own stomachs, then poop it out in a protected chamber. After 45 days of fungal decomposition, older termites eat this mix. By the end, the wood is almost completely digested.
"The cultivation of fungus for food [by termites] is one of the most remarkable forms of symbiosis on the planet," said Cameron Currie, a professor at the University of Wisconsin, Madison and researcher with the DOE's Great Lakes Bioenergy Research Center.
Scientists assumed that the majority of the decomposition occurred outside of the gut, discounting the work of the younger termites. But Hongjie Li, a biologist at the University of Wisconsin, Madison, wondered if younger insects deserved more credit. He found that young workers' guts break down much of the lignin. In addition, the fungi involved don't use any of the typical enzymes white or brown rot fungi produce. Because the fungi and gut microbiota associated with termites have evolved more recently, this discovery may open the door to new innovations.
From the Lab to the Manufacturing Floor
From the forest floor to termite mounds, fungal decomposition could provide new tools for biofuels production. One route is for industry to directly produce the fungal and associated microbiota's enzymes and other chemicals. When they analyzed termite-fungi systems, scientists found hundreds of unique enzymes.
"We're trying to dig into the genes to discover some super enzyme to move into the industry level," said Li.
A more promising route may be for companies to transfer the genes that code for these enzymes into organisms they can already cultivate, like yeast or E. coli. An even more radical but potentially fruitful route is for industry to mimic natural fungal communities.
For millions of years, fungi have toiled as short-order cooks to break down wood and other plants. With a new understanding of their abilities, scientists are helping us comprehend how essential they are to Earth's past and future.
Photo:
- Author: Ben Faber
Occasionally plants show up in our office for identification and no one in the office knows what it is. So it's sent off to to others who might know. This was the case of a perennial amaranth, also called goosefoot for some reason. The is Chenopodium californicum, also know as Blitum californicum.
Like other amaranths, it can be upright to 3 feet in height, or if mowed or grazed be more flattened or decumbent. It has a thick, fleshy stem that along with the leaves can be eaten. I guess pigs like it, because it's also called pigweed.
The leaves look sort of lettuce like, which gives it another name - Indian Lettuce.
The stem has also been used for making soap, which gives it another name of soaproot. Which is not to be confused with another soaproot, Chloragulum. Plant names can be confusing.
Chenopodium californicum, Blitum,goosefoot, pigweed, soaproot grows in the chaparral on slopes and in foothill woodlands, mainly along the coast.
Calflora: http://www.calflora.org/cgi-bin/species_query.cgi?where-calrecnum=1968
Plants for a Future: https://www.pfaf.org/USER/Plant.aspx?LatinName=Chenopodium+californicum
- Author: Ben Faber
For centuries, the prevailing science has indicated that all of the nitrogen on Earth available to plants comes from the atmosphere. But a study from the University of California, Davis, indicates that more than a quarter comes from Earth's bedrock.
The study, to be published April 6 in the journal Science, found that up to 26 percent of the nitrogen in natural ecosystems is sourced from rocks, with the remaining fraction from the atmosphere.
Before this study, the input of this nitrogen to the global land system was unknown. The discovery could greatly improve climate change projections, which rely on understanding the carbon cycle. This newly identified source of nitrogen could also feed the carbon cycle on land, allowing ecosystems to pull more emissions out of the atmosphere, the authors said.
"Our study shows that nitrogen weathering is a globally significant source of nutrition to soils and ecosystems worldwide," said co-lead author Ben Houlton, a professor in the UC Davis Department of Land, Air and Water Resources and director of the UC Davis Muir Institute. "This runs counter the centuries-long paradigm that has laid the foundation for the environmental sciences. We think that this nitrogen may allow forests and grasslands to sequester more fossil fuel CO2 emissions than previously thought."
WEATHERING IS KEY
Ecosystems need nitrogen and other nutrients to absorb carbon dioxide pollution, and there is a limited amount of it available from plants and soils. If a large amount of nitrogen comes from rocks, it helps explain how natural ecosystems like boreal forests are capable of taking up high levels of carbon dioxide.
But not just any rock can leach nitrogen. Rock nitrogen availability is determined by weathering, which can be physical, such as through tectonic movement, or chemical, such as when minerals react with rainwater.
That's primarily why rock nitrogen weathering varies across regions and landscapes. The study said that large areas of Africa are devoid of nitrogen-rich bedrock while northern latitudes have some of the highest levels of rock nitrogen weathering. Mountainous regions like the Himalayas and Andes are estimated to be significant sources of rock nitrogen weathering, similar to those regions' importance to global weathering rates and climate. Grasslands, tundra, deserts and woodlands also experience sizable rates of rock nitrogen weathering.
GEOLOGY AND CARBON SEQUESTRATION
Mapping nutrient profiles in rocks to their potential for carbon uptake could help drive conservation considerations. Areas with higher levels of rock nitrogen weathering may be able to sequester more carbon.
"Geology might have a huge control over which systems can take up carbon dioxide and which ones don't," Houlton said. "When thinking about carbon sequestration, the geology of the planet can help guide our decisions about what we're conserving."
MYSTERIOUS GAP
The work also elucidates the "case of the missing nitrogen." For decades, scientists have recognized that more nitrogen accumulates in soils and plants than can be explained by the atmosphere alone, but they could not pinpoint what was missing.
"We show that the paradox of nitrogen is written in stone," said co-leading author Scott Morford, a UC Davis graduate student at the time of the study. "There's enough nitrogen in the rocks, and it breaks down fast enough to explain the cases where there has been this mysterious gap."
In previous work, the research team analyzed samples of ancient rock collected from the Klamath Mountains of Northern California to find that the rocks and surrounding trees there held large amounts of nitrogen. With the current study, the authors built on that work, analyzing the planet's nitrogen balance, geochemical proxies and building a spatial nitrogen weathering model to assess rock nitrogen availability on a global scale.
The researchers say the work does not hold immediate implications for farmers and gardeners, who greatly rely on nitrogen in natural and synthetic forms to grow food. Past work has indicated that some background nitrate in groundwater can be traced back to rock sources, but further research is needed to better understand how much.
REWRITING TEXTBOOKS
"These results are going to require rewriting the textbooks," said Kendra McLauchlan, program director in the National Science Foundation's Division of Environmental Biology, which co-funded the research. "While there were hints that plants could use rock-derived nitrogen, this discovery shatters the paradigm that the ultimate source of available nitrogen is the atmosphere. Nitrogen is both the most important limiting nutrient on Earth and a dangerous pollutant, so it is important to understand the natural controls on its supply and demand. Humanity currently depends on atmospheric nitrogen to produce enough fertilizer to maintain world food supply. A discovery of this magnitude will open up a new era of research on this essential nutrient."
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UC Davis Professor Randy Dahlgren in the Department of Land, Air and Water Resources co-authored the study.
The study was funded by the National Science Foundation's Division of Earth Sciences and its Division of Environmental Biology, as well as the Andrew W. Mellon Foundation.
Photo: The stuff that makes leaves green
- Author: Ben Faber
Several Florida blueberry growers have recently reported flower bud damage and corresponding fruit loss, in some cases up to 50% on certain affected cultivars. These reports have focused primarily on Emerald, Farthing and Meadowlark, although other cultivars may have also been affected to some degree. There could be multiple reasons for flower bud damage and the resulting fruit loss, including hydrogen cyanamide and freeze damage. However, in several cases this year it is believed that this type of damage has been caused by blueberry gall midge.
High populations of blueberry gall midge in blueberry can result in significant flower bud injury and reduce fruit set and yield. Females lay eggs in floral and vegetative buds just after bud swell. Gall midge larvae then feed on developing leaf and floral buds. Affected floral buds develop a dry, shriveled appearance and will often disintegrate (Figure 1). Damaged leaf buds are characterized by misshapen leaves and blackened and distorted shoot tips (Figure 2). When the terminal bud on a shoot is injured or killed, shoot elongation growth may be inhibited with excessive later branching occurring just below the damage terminal bud. Weather may impact the density of gall midge populations, with warmer temperatures > 60o F resulting in early emergence. Furthermore, re-infestation of previously infested areas is common if management action is not taken when gall midge injury is observed.
Growers should be aware of the possibility of gall midge damage in their fields this season, resulting in floral bud death and lower fruit set. Dr. Oscar Liburd, University of Florida blueberry entomologist, is preparing a bulletin to be released very soon with current gall midge management recommendations to be implemented after this season's harvest is complete. Until this extension bulletin is ready to be published, growers can view pesticide recommendations for gall midge in The Blueberry News magazine.
High populations of blueberry gall midge can result in significant flower bud injury and reduce fruit set and yield, Phillips points out. The following are his scouting tips for this pest.
- Females lay eggs in floral and vegetative buds just after bud swell. Gall midge larvae then feed on developing leaf and floral buds. Affected floral buds develop a dry, shriveled appearance and will often disintegrate.
- Damaged leaf buds are characterized by misshapen leaves and blackened and distorted shoot tips. When the terminal bud on a shoot is injured or killed, shoot elongation growth may be inhibited with excessive later branching occurring just below the damage terminal bud. Weather may impact the density of gall midge populations, with warmer temperatures (greater than 60°F) resulting in early emergence. Furthermore, re-infestation of previously infested areas is common if management action is not taken when gall midge injury is observed.
Is this something that California growers should be concerned about? To my knowledge these midges have not been reported in California. We also don't use hydrogen cyanamide which may be contributing to the problem. With plant material and people moving around, though, it might show up and be a problem. I never thought blueberry rust would show up in California, but as the crop has become more widespread, it has showed up. Ever alert.
Alert from UF/IFAS Blueberry Extension Coordinator Doug Phillips:
http://entnemdept.ufl.edu/creatures/fruit/blueberry_gall_midge.htm
https://pubag.nal.usda.gov/download/10784/PDF
Photo: Blueberry Gall Midge, Dasineura oxycoccana