Posts Tagged: ramorum
Citizens Concerned about Sudden Oak Death in San Luis Obispo County
From the ANR News Blog Central Coast residents, officials, ranchers and representatives of...
Mature Compost Does NOT Kill Phytophthora
A recent article in California Agriculture highlights something that we have found in raw organic materials that have been used in mulches for controlling Avocado Root Rot – Phytophthora cinnamomi. The most active stage of a material in the process of composting, is the initial one where all the bacteria and fungi are fighting to consume the easily decomposable sugars and light fraction organics. That's when the material heats up and various gases, such as ethylene, ammonia and others are released. This is the most competitive time in decomposition and Phytophthora just can't compete. In fact, it becomes a food source for the antagonistic fungi, since its cell wall is made of cellulose the material that many leaves are made of. In releasing exudates to decompose cellulose, the Phytophthora is decomposed, as well. As the cellulose is decomposed and disappears more resistant materials remain. A mature compost, is therefore a much more stable material than a raw one. It still has nutritional benefits, as well as physical effects on soil when it is incorporated, but has a lesser impact on Phytophthora.
Compost is used as a soil amendment, largely because it is relatively stable biologically and has nutritional/physical effects. Incorporating raw organic matter into the soil and then planting has its restrictions and should be done cautiously. But as a mulch (material applied to the soil surface) there are fewer problems, as long as some common sense is used. Like don't pile it up against plant stems which keeps moisture and conditions for disease around the plant crown. And there are several other qualifiers, such as don't apply it so thickly that the soil never dries out and becomes a problem in walking across it.
So, read this interesting story of what happens to Phytophthora when introduced into a mature compost:
This is also a great web site to read about other UC related agriculture and natural resource research. Sign up.
compost pile
Sudden Oak Death Moving to Urban Areas; 3 Steps to Protect Oaks
Drought is decreasing but not defeating the pathogen that causes sudden oak death, according to a...
Coast redwoods increasingly susceptible to fire damage
Millions of trees, including tanoaks, coast live oak, California bay laurels, and many other forest species have been killed by sudden oak death in coastal areas of central and northern California, and Oregon. The pathogen, Phytophthora ramorum, was first linked to the massive tree death in the mid-1990s.
David Rizzo, professor in the Department of Plant Pathology at UC Davis, and his research team are studying how the coastal forest ecology is changing since sudden oak death appeared, and why coast redwoods (Sequoia sempervirens) are subsequently so much more susceptible to fire.
It is the presence of the sudden oak death pathogen in forests that poses heavier fire risks for redwoods.
“If redwoods didn’t live in forests affected by the disease, they could withstand fires just fine,” says Margaret Metz, a postdoctoral research scholar working with Rizzo.
According to Rizzo, “The disease likely created more fuel for wildfires as dead tanoak branches fell. The loss of the oaks also would have decreased the amount of shade, drying out the forest and turning it into a tinder box, one not even redwoods could survive.”
A real key, though, is the finding that dead tanoaks, still standing, carry flames high into tree canopies, scorching the crowns of adjacent redwood trees. It’s this crown injury that is believed to have caused so many redwood trees to die in a number of fires that occurred in 2008.
Rizzo, noting that an increase in fire severity is resulting from climate change and global movement of species, says, “There may be all sorts of consequences, among them, dead and dying coast redwoods.”
Additional information:
- California's iconic redwoods in danger from fire and infectious disease. National Science Foundation report on Rizzo group’s work, August 2013
- The effects of sudden oak death and wildfire on forest composition and dynamics in the Big Sur ecoregion of coastal California. General technical report
- Ecology research article, Ecological Society of America
- California Oak Mortality Task Force website
Summary of the 5th Sudden Oak Death Science Symposium
The 5th Sudden Oak Death Science Symposium, held in Petaluma, CA June 19 – 22, 2012, brought together researchers, regulators, land managers, and industry representatives from throughout the world working on Sudden Oak Death (SOD), Phytophthora ramorum (the pathogen known to cause SOD), and other related forest and nursery pests. The Symposium included 52 talks and 25 posters from top researchers around the globe as well as a “SOD: Biosecurity Concerns and Forest Restoration” field trip, where attendees heard about international plant hunters and biosecurity risks related to plant hunting and walked through a local preserve, learning about long-term system changes and restoration efforts following SOD outbreaks. There was also a community “Ask the Expert” evening session where the public was able to talk one on one with researchers and outreach specialists, and a special tanoak session was offered on Friday, focusing on the history, values, and ecology of tanoak.
Highlight findings from the meeting included the discovery of a 4th P. ramorum lineage, the announcement that pathogen sporulation has been found on non-symptomatic Japanese larch needles, and learning that 85 percent of the Marin Municipal Water District’s susceptible habitat is now infested.
Picture of the field trip at Bouverie Wildflower Preserve during a restoration conversation.
Field trip at Quarryhill Botanical Garden.
Photo taken during the public "Ask an Expert" session at the symptoms station.
Treatment training station at the "Ask the Expert" evening session.
Thomas Brown, the Native American speaker for the day. He is from the Elem Indian Colony Pomo Nation of Lake County and Circle of Native Minds Wellness Center.
If you missed the Symposium, be sure to visit the website (http://ucanr.org/sites/sod5/) where you can access the agenda, book of abstracts, and link to the archived live stream that was made available throughout the meeting for those unable to attend.