Features

After SOD Arrives in Your Area

Doug Schmidt All Posts, Features
After SOD Arrives in Your Area

Topic:

Once SOD infections have arrived, what can be done?

Recommendation:

  •  If SOD is present in a portion of the property remember to:
    • Schedule all landscaping and construction operations to occur first in the SOD-free area.
    • Ensure that equipment is cleaned after work in the SOD infested area.
  • Minimize all activities and operations in the Spring. Fall is the best work to avoid spreading infection through disturbance. Pruning of large branches and stems in multi-stemmed oaks should occur possibly in late November, and never in February-June.
  • If the property is downwind and down slope from a dense mixed forest with significant infestation, ensuring that water runoff is properly channeled may be beneficial to avoid spread of the disease by water.
  • Oaks that have a buffer area of at least 10 yards (10m) around the main trunk, devoid of any bay laurels or rhododendrons, are less likely to become infected. Identify valuable oaks and clear a 10 yard area around them by removing all small and medium bays, or by pruning large bay laurel branches of large trees that may come into the “buffer”. Bay laurels need to be treated with systemic herbicides at least a couple of weeks before being cut down, to minimize re-sprouting. Avoid all overhead irrigation and summer irrigation near oaks. For oaks over 32″ in diameter (80cm), 50-65 ft (15-20m) may be appropriate.
  • If oaks are not infected they can be protected with a single yearly treatment of phosphonate in November and early December. If treating in the Spring for the first time, repeat in the Fall and switch to a single yearly Fall treatment. Treatments are not a cure but will increase resistance in about three quarters of treated plants.
  • Phosphonate treatments have no known damaging side-effects on the environment and their action enhances the natural defense mechanisms in the plant. If injecting the product, we recommend alternating with bark applications every other year, to minimize wounding.sod4
  • Ensure you or your tree-care specialist has attended a workshop on how to properly apply the product. Topical bark applications require:
    • Topical bark applications require removal of thick moss and tarping of shrubs or other small plants nearby.
    • Injections require knowledge of appropriate timing, number of injections per tree, and injection technique, injections should not be performed in the Spring.
  • No chemical treatment of bay trees is known to be effective, and other alleged treatments of oaks have been shown to be ineffective in controlled experiments.
  • Additional treatments such as carving or scribing the infection out of an oak, or amending the soil near oaks with a thin layer of compost are still untested and we cannot recommend them. In addition, wounds may be detrimental to the tree and facilitate further SOD infection. To minimize such risk do not attempt to remove lesions in the Spring when infection potential is high. Lesion removal from oaks is still completely untested and could have unknown side effects.

Research behind the Recommendation:

The arrival of SOD in an area may be very gradual over time or may occur in a single year. Knowledge of SOD biology and disease distribution may help you prepare for the arrival of SOD and may allow time to protect valuable trees. The SODmap Mobile app, available for iPhone and Android, is an invaluable tool for visualizing SOD infections on the ground, in real time.

Dead oaks represent a significant hazard to people and property and increased fire hazard, however oaks that are infected by SOD and are apparently green may be equally hazardous. In SOD-infested areas, monitor closely oaks and tanoaks that are near homes, access roads, paths, yards, and play areas, and remove trees that show significant SOD symptoms and may be hazardous due to their location. Dead standing oaks, whether still green or brown represent a serious hazard for homeowners and are documented to fuel hotter fires that can kill medium sized redwoods.

UC Berkeley researchers have surveyed a large number of Coast Live Oaks, Tanoaks, and California Bay Laurels and determined that significant natural resistance to SOD is absent or very rare. However all three species have individual plants that may be more tolerant than others. Currently resistant plants are not available on the market, but several oak species (Valley oaks Blue oaks, Oregon oaks) are not susceptible to SOD.

 

Links and References:

Before SOD Arrives in Your Area

Doug Schmidt All Posts, Features
Before SOD Arrives in Your Area

Topic:

What to do before SOD arrives in your area.

Recommendation:

To help prevent the spread of SOD in  ornamental plants you purchase, ensure that they come from a facility that is regularly tested for P. ramorum. Make sure that wood from trees in SOD-infected areas is not moved to uninfected locations. Ensure that shoes, vehicle tires, and tools are free of soil and organic debris that might harbor the disease.

Careful brushing tools or air-blowing all soil and organic matter from them is normally sufficient to eliminate the risk of contagion. If driving on dirt roads during the rainy season in highly infested areas, wash the vehicle before returning home or visiting SOD-free areas. Preventative application of phosphonate compounds may help slow the spread of the disease in uninfected trees.

Familiarize yourself with the distribution of SOD using our SOD Disease Distribution maps, SODmap Mobile app, or OakMapper, and learn to identify early symptoms on bay laurels and tanoaks. The California Oak Mortality Task Force is a comprehensive source for the latest information on SOD. Contact your county Department of Agriculture officer for testing and participate in the SOD Blitz Survey Project held each year from April to June.

Research behind the Recommendation:

P. ramorum is dispersed aerially usually at short distances 100 yards or less, but occasionally up to 1-2 miles. Movement of infected plants or plant parts, soil, and water may lead  to new infestations. The current distribution of SOD is updated on our maps each year. Only a lab test can confirm SOD and early detection of SOD is best to maximize chances of slowing its spread.

Links and References:

Heterobasidion: A Disposition of Two North American Species

Doug Schmidt All Posts, Features
Heterobasidion: A Disposition of Two North American Species

What’s in a name? Two of the most serious wood pathogens of conifers worldwide have been renamed by U.C. Berkeley and US Forest Service scientists. Because of the significant economic and scientific importance of these organisms, and because one of them was introduced in Europe by US soldiers during World War II, this is a long-awaited publication.

Heterobasidion occidentale and H. irregulare – a disposition of two North American species.
Article

Island Biogeography and Fire – Kabir Peay

Doug Schmidt All Posts, Features
Island Biogeography and Fire – Kabir Peay

Island Biogeography and Fire Affecting Ectomycorrhizal Colonization of “Tree Islands”

Ecology 2010
Evidence of dispersal limitations in soil microorganisms . . .
Plant Soil 2010
Testing the ecological stability of ectomycorrhizal symbiosis . . .
Journal of Ecology 2009
Spore heat resistance plays an important role . . .
Ecology Letters 2007
A strong species-area relationship for . . .

Fungi are a critical component of the diversity and function of terrestrial ecosystems. Pathogens and mycorrhizal fungi receive a large, direct share of net primary productivity, and wood decay and mycorrhizal fungi play a critical role in the cycling of key plant macronutrients. However, the biodiversity and community dynamics of these organisms are still poorly resolved, as is the extent to which they control plant and animal community structure. For my thesis work I used molecular, GIS, and isotopic techniques to examine a number of topics related to the community assembly and symbiotic dynamics of ectomycorrhizal fungi.

The first part of my thesis applied the theory of island biogeography to ectomycorrhizal “tree-islands” ­ patches of host trees embedded in a non-host matrix ­ as a way to look for evidence that immigration and extinction affect ectomycorrhizal assemblages. These tree-islands generally conformed to the expectations of island biogeography theory ­ larger tree islands housed more species of ectomycorrhizal fungi, and more isolated tree islands had fewer species of ectomycorrhizal fungi. This work led to one of the few published species-area relationships for fungi and provided good evidence for a competition-colonization tradeoff in ectomycorrhizal communities. The second portion of my thesis work used manipulative experiments to assess the effects of fire on ectomycorrhizal assemblage structure and host plant relations. We found that simulated fire simplified and shifted the ectomycorrhizal assemblage colonizing seedlings. We also found that the species with the greatest increase in abundance from simulated fire also had the most heat tolerant spores, indicating that this may be an important mechanism for changes in post-fire assemblage structure. We also found evidence that the ectomycorrhizal plant-fungal symbiosis remained mutualistic despite dramatic changes in the soil environment after simulated fire.

From this work we have found evidence for the importance of both stochastic ecological processes, such as immigration, as well as deterministic ecological processes, such as niche partitioning. Because most assemblages are likely affected by both sets of processes, I believe a key challenge in moving fungal community ecology forward is to synthesize results from both types of studies and determine the spatial and temporal scales at which they are most important in determining species’ abundance and distribution.

UC Berkeley & the European Food Safety Authority

Doug Schmidt All Posts, Features
UC Berkeley & the European Food Safety Authority

 

2011 EFSA 16th Scientific Colloquium
EFSA Scientific Opinion on Pest Risk Analysis...
EFSA Scientific Opinion on Phytophthora ramorum
Testing the ecological stability of ectomycorrhizal symbiosis . . .

Parma , 9 June 2011 – Experts from around the world gather to discuss emerging risks in plant health More than 100 international experts gathered in Parma on 9-10 June for an open scientific debate on key issues related to the identification of emerging risks in plant health. The European Food Safety Authority’s 16th Scientific Colloquium attracted risk assessors, risk managers, scientists and stakeholders from 31 countries, including 19 EU Member States, 7 candidate countries, Canada, Georgia, Japan, Norway, and the United States.

The event was attended by representatives of prominent international organisations concerned with plant health such as the International Plant Protection Convention (IPPC), the European and Mediterranean Plant Protection Organisation (EPPO), and the Centre for Agricultural Bioscience International (CABI). Johannette Klapwijk, from the International Biocontrol Manufacturers’ Association (IBMA), gave a keynote presentation.

Representatives from important stakeholders, including the association of European farmers and agri-cooperatives (COPA-COGECA), also contributed to the discussions. Scientists from the European Commission’s Joint Research Centre as well as Commission officials were present.

The colloquium was held against the background of a global rise in the number of new pests and the emergence of pests not previously considered a threat to plant health in the EU. Meeting these challenges requires a rapid, robust system to identify risks as early as possible, and to communicate risk assessments to risk managers without delay. The theme of the colloquium was “a change can trigger a risk” and the presentations and discussions examined these triggers at various levels: from the micro level of plant-pest interactions, to the macro levels of crop cultivation, trade and climate change. Delegates formed discussion groups to debate key issues such as the implications of changes in forestry and agriculture practices; the importance of changing patterns in trade, food consumption and land use; and the relationship between climate change and new threats to plant health.

Elzbieta Ceglarska, the Head of EFSA’s Plant Health Unit, said: “The colloquium dealt with topics of significant importance for the development of EFSA’s work on emerging risks in plant health. The quality of the discussion was exceptional. “We have shed new light on how best to identify new risks through data collection, anticipate them through research, and analyse the implications through risk assessment. EFSA has come away with valuable material with which to further develop methodologies for assessing emerging risks in the area of plant health.”

Tracks of an Oak Killer

Doug Schmidt All Posts, Features
Tracks of an Oak Killer
Story and Video
Main Story
Podcast
Podcast

 

About the Author: Erin Loury
B.S. (biology) University of California, Davis
M.S. (marine science) California State University/Moss Landing Marine Laboratories
Internship: Los Angeles Times (Kaiser Family Foundation health reporting internship)

This story on sudden oak death was my final project for the graduate program in science communication at UC Santa Cruz. It was a wonderful opportunity to delve into a topic that I previously knew so little about. I was fascinated to learn about the waterborne disease organism, the role of bay laurels as carriers, and the ability to protect a tree with Agri-fos. I am very thankful to Matteo Garbelotto for making this story possible. Matteo’s willingness to talk at length about the disease was crucial in helping me develop my understanding. My eye-opening trip into the field to see sudden oak death up close also helped me frame the story. I greatly enjoyed attending a SOD Blitz to record material for the podcast that accompanies the story. Reporting and writing this feature has helped deepen my appreciation for the beauty, fragility, and importance of oak trees.