ScienceDaily (May 8, 2012) — A plant pathologist at the University of California, Riverside has identified a fungus that has been linked to the branch dieback and general decline of several backyard avocado and landscape trees in residential neighborhoods of Los Angeles County.

The fungus is a new species of Fusarium. Scientists are working on characterizing its specific identification. It is transmitted by the Tea Shot Hole Borer (Euwallacea fornicatus), an exotic ambrosia beetle that is smaller than a sesame seed. The disease it spreads is referred to as “Fusarium dieback.”

“This beetle has also been found in Israel and since 2009, the beetle-fungus combination has caused severe damage to avocado trees there,” said Akif Eskalen, an extension plant pathologist UC Riverside, whose lab identified the fungus.

To date, the Tea Shot Hole Borer has been reported on 18 different plant species worldwide, including avocado, tea, citrus, guava, lychee, mango, persimmon, pomegranate, macadamia and silk oak.

Eskalen explained that the beetle and fungus have a symbiotic relationship.

“When the beetle burrows into the tree, it inoculates the host plant with the fungus it carries in its mouth parts,” he said. “The fungus then attacks the vascular tissue of the tree, disturbing water and nutrient flow, and eventually causing branch dieback. The beetle larvae live in galleries within the tree and feed on the fungus.”

Although the beetle was first detected in Los Angeles County in 2003, reports of its negative impact on tree health were paid no attention until February 2012, when Eskalen found both the beetle and fungus on a backyard avocado tree showing dieback symptoms in South Gate, Los Angeles County. The Agricultural Commissioner of Los Angeles County and the California Food and Drug Administration have confirmed the identity of the beetle.

“This is the very same fungus that caused avocado dieback in Israel,” Eskalen said. “The California Avocado Commission is concerned about the economic damage this fungus can do to the industry here in California.

“For now, we are asking gardeners to keep an eye on their trees and report to us any sign of the fungus or beetle,” he added. “Symptoms in avocado include the appearance of white powdery exudate in association with a single beetle exit hole on the bark of the trunk and main branches of the tree. This exudate could be dry or it can appear as a wet discoloration.”

A team of UCR scientists has been formed to study Fusarium dieback in Southern California. Eskalen and Alex Gonzalez, a field specialist, are already conducting a survey to determine the extent of the beetle infestation and the likely extent of the fungus infection in avocado trees and other host plants. Richard Stouthamer, a professor of entomology, and Paul Rugman-Jones, an associate specialist in entomology, are studying the biology and genetics of the beetle.

Members of the public can report sightings of the Tea Shot Hole Borer and signs of Fusarium dieback by calling (951) 827-3499 or emailing aeskalen@ucr.edu.

Multiple members of the California ReLeaf Network were awarded more than $4.5 million in grant funding from the Strategic Growth Council last week to support urban greening projects and planning in the Central Valley and Southern California.

Numerous Network groups will be utilizing urban greening project funds to develop green space at several schools and schoolyards in California by replacing asphalt and concrete with permeable surfaces, bioswales, low mow/low maintenance grasses, gardens, native landscaping, understory and shade trees. Award recipients included the LA Conservation Corps, Hollywood Beautification Team and the Sacramento Tree Foundation.

In addition, TreePeople and North East Trees joined the LA Conservation Corps in securing planning grants that will support urban greening planning for Baldwin Hills, La Brea, Downtown San Pedro, Inglewood, and Lennox.

Finally, Urban Tree Foundation partnered with the City of Visalia and the City of Hanford to restore portions of Mill Creek, and plant street trees in downtown Hanford, respectively.

In total, six Network groups picked up 10 urban greening grants totaling almost $4.6 million, or more than 22%, of the entire pot for available in this grant cycle.

The final awards approved by SGC last week in the 2011-12 grant cycle for Network Groups are as follows:

By DOUGLAS M. MAIN

It’s important to respect your elders, children are reminded. It seems that this goes for trees, too.

Big, old trees dominate many forests worldwide and play crucial ecological services that aren’t immediately obvious, like providing habitat for a wide range of organisms, from fungi to woodpeckers.

Among their many other invaluable roles, the oldsters also store a lot of carbon. In a research plot in California’s Yosemite National Park, big trees (those with a diameter greater than three feet at chest height) account for only 1 percent of trees but store half of the area’s biomass, according to a study published this week in PLoS ONE.

To read the full article published in the New York Times, click here.

On an Urban Heat Island, Zippy Red Oaks

By DOUGLAS M. MAIN

The New York Times, April 25, 2012

Red oak seedlings in Central Park grow up to eight times faster than their cousins cultivated outside the city, probably because of the urban “heat island” effect, Columbia University researchers report.

The researchers planted seedlings of the native red oak in the spring of 2007 and 2008 in four places: in northeastern Central Park, near 105th Street; in two forest plots in the suburban Hudson Valley; and near the city’s Ashokan Reservoir in the Catskill foothills about 100 miles north of Manhattan. By the end each of summer, the city trees had put on eight times more biomass than those raised outside the city, according to their study, published in the journal Tree Physiology.

“The seedlings grew much larger in the city, with decreasing growth as you get farther from the city,” said the study’s lead author, Stephanie Searle, who was a Columbia University undergraduate when the research began and is now a biofuels policy researcher at the International Council on Clean Transportation in Washington.

The researchers hypothesized that Manhattan’s warmer temperatures — up to eight degrees higher at nighttime than in rural surroundings — could be a primary reason for the Central Park oaks’ faster growth rates.

Yet temperature is obviously only one of the differences between rural and urban sites. To isolate the role played by the thermostat, the researchers also raised oaks in a laboratory setting where all conditions were basically the same, except for the temperature, which was altered to mimic conditions from the different field plots. Sure enough, they observed faster growth rates for oaks raised in hotter conditions, similar to those seen in the field, Dr. Searle said.

The so-called urban heat island effect is often discussed in terms of potentially negative consequences. But the study suggests it could be a boon to certain species. “Some organisms may thrive on urban conditions,” another author, Kevin Griffin, a tree physiologist at Lamont-Doherty Earth Observatory at Columbia, said in a statement.

The results parallel those of a 2003 study in Nature that found greater growth rates among poplar trees raised in the city than among those grown in the surrounding countryside. But the current study went farther by isolating the effect of temperature, Dr. Searle said.

Red oaks and their relatives dominate many forests from Virginia to southern New England. The experience of Central Park’s red oaks could yield clues to what might happen in forests elsewhere as temperatures climb in decades to come with the advance of climate change, the researchers suggested.

The NPCI program funds multi-stakeholder projects that focus on the conservation of native plants and pollinators under any of the following six focal areas: conservation, education, restoration, research, sustainability, and data linkages. There is a strong preference for “on-the-ground” projects that provide plant conservation benefits according to the priorities established by one or more of the funding federal agencies and according to the PCA strategies for plant conservation.

Eligible applicants include 501(c) nonprofit organizations and local, state, and federal government agencies. For-profit businesses and individuals are not eligible to apply directly to the program but are encouraged to work with eligible applicants to develop and submit proposals. Organizations and projects that have received funding and concluded their work successfully under this program are eligible and encouraged to re-apply.

It is anticipated that the initiative will award a total of $380,000 this year. Individual awards typically range from $15,000 to $65,000, with some exceptions. Projects require a minimum 1:1 non-federal match by project partners, including cash or in-kind contributions of goods or services (such as volunteer time).