The "perfect storm" of prolonged drought, hot temperatures and both invasive non-native and native tree killing insects is in the process of creating a potentially epoch changIng natural system shift in southern California................."In Los Angeles, the native trees of the Santa Monica Mountains have evolved and are adapted over thousands of years to prolonged dry periods of drought................."However, the tree die-off we are experiencing now is unprecedented in modern history, scientists say"............Days exceeding 95 degrees have increased significantly............. In combination with an unprecedented number of both invasive non-native/alien and native insects boring into trees, the Santa Monica Mountains that ring "the city of angels" are seeing thousands of native oaks, sycamores and other native tree species snuffed out..............."New surveys of the 154,000-acre Santa Monica Mountains National Recreation Area conducted by remote sensing instruments on NASA aircraft and teams on the ground reveal a loss of about 9,100 — or 6% — of coast live oaks, and 114,000 — or 32% — of riparian trees including sycamores, alders and willows during the past 7 years"............. "About 38% of the area's chaparral plant community has also perished"............"Further ripple effects cascading on up into the native animal, fish, bird and reptile community seem to be already underway"..............."For example, mayflies, which float on the surface and are an easily accessible food for fish and frogs, have been replaced by tiny chironomid midges, which spend much of their lives hiding in sunken leaves"................."Whether Topanga Canyon's fish and frogs adapt to the shift remains to be seen, scientists say."..................."Dying trees and shrubs have exacerbated the plight of Western pond turtles, California's only native freshwater turtle"..............."The roughly 200 pond turtles left in the Santa Monicas eat and reproduce in water, and spend much of their lives hunkered down in chaparral and leaf litter"................."With fewer places for them to hide from predators like raccoons and ravens, we're finding more and more pond turtles with their eyes pecked out and missing legs"

https://www.hub-la.com/features/tree-killing-bugs-invading-southern-california/

Southern California trees under threat from infestation

By 

By Keith Scheuer; 4/24/18

From the mountains to the sea and throughout Southern California, millions of trees have succumbed to a mixed assault of insects, bacterial and fungal infestation, climate change, and insufficient water.

DEAD OAK IN THE SANTA MONICAS

The numbers are staggering. The U.S. Forest Service reports that bark beetles had killed more than 102 million trees in the Sierra Nevada by the end of 2016. More than 200 kinds of bark beetles reside in California, about 20 of which are invasive. Most attack pines and other conifers, but some also go after broad-leaf trees.

In the Santa Monica Mountains, goldspotted oak borer beetles have destroyed several thousand native oaks, and approximately 30,000 more in San Diego County.

Another kind of beetle called the Kuroshio shot hole borer has destroyed almost 150,000 willows in Tijuana River Valley Regional Park. In many parts of Orange County, vast, leafy groves of alders, Liquidambars and sycamores are being decimated by the polyphagous shot hole borer, a close cousin of the Kuroshio. These two borers look identical but have differing DNA. Collectively, they are known as invasive shot hole borers.

These bugs have also invaded The Los Angeles County Arboretum and Botanic Garden in Arcadia. The Arboretum’s Frank McDonough estimates that more than 900 of its trees and shrubs have been attacked by borers, and that roughly 200 trees have been completely lost. The dead include 20 or 30 large Eucalyptus, destroyed by the Eucalyptus longhorned borer.

He says the climate of Southern California requires a more pragmatic sense of what can grow here.

BORER HOLES

 “People are going to have to adapt a new aesthetic that uses plant material and trees that are more climate appropriate,” McDonough says. “The geology [in] places like the Los Angeles basin is such that the groundwater is over 100 feet deep and so impossible for trees to get their roots into. If you look at pictures of the L.A. basin before it was hugely developed it was a treeless plain.”

According to a study conducted by U.S. Forest Service researcher Greg McPherson, invasive shot hole borers threaten to kill nearly 38% of all trees in Los Angeles, Orange, San Bernardino and Riverside Counties, about 27 million trees total.

“Many of the trees we grow evolved in temperate climates and can’t tolerate the stress of drought, water restrictions, higher salinity level in recycled water, wind and new pests that arrive almost daily,” McPherson says.

Many kinds of killer

Beetles are just one group of culprits killing trees. Among many others are citrus psyllids, glassy-winged sharpshooters and palm weevils.

These and similar pests threaten a variety of native trees, decorative trees, and those cultivated for agriculture, including avocados, citrus and palms.

According to entomologists Paul Rugman-Jones and Richard Stouthamer of the University of California Riverside, the invasive Kuroshio and polyphagous shot hole borers most likely came from Vietnam and Taiwan and were first discovered in California in 2003 and 2013, respectively. Kuroshio are about as long as a grain of rice. Female polyphagous borers are the size of Lincoln’s nose on a penny, the males much smaller.

According to the UC Riverside researchers, these invaders have shown rapid population growth in California and elsewhere. In 2012, the polyphagous borers were confined to southern Los Angeles County, Orange County and the extreme southwestern edge of San Bernardino County. By 2016, their range extended from San Luis Obispo to the Mexican border.

SHOT-HOLE BORER

These foreigners are not fussy about where they hang their hats.

Akif Eskalen, a plant pathologist at UC Riverside and his colleagues have identified 62 known reproductive hosts in California for invasive shot hole borers, including species of elder, maple, sycamore, willow, avocado, oak, cottonwood, alder, chestnut, holly, camellia, acacia, wisteria, fig, beech, poplar, buckeye, palm, coral, magnolia and jacaranda.

Different bugs kill trees differently. Bark beetles eat the inner bark. Borers dine on a fungus (fusarium dieback) that they introduce into host trees. The fungus disrupts the flow of water and nutrients to the host tree, eventually killing it.

Eskalen notes, “Trees may be more susceptible if they are already under stress due to other pests, diseases, or environmental conditions or are in close proximity to an existing infestation.”

Researchers with the Forest Service attribute the great slaughter of local trees by these insects to our low rainfall and mild winters in recent years. Too little water stressed the host trees and weakened their ability to resist predators; mild winters allowed the predators to survive and spread in far greater numbers than they otherwise would have.

“Among bark beetles and wood borers, higher than average winter minimum temperatures and drought are correlated with bark beetle outbreaks. Higher winter temperatures, and longer growing seasons are expected to become increasingly common into the future,” according to Forest Service experts Haiganoush K. Preisler, Nancy E. Grulke, Zachary Heath and Sheri L. Smith.

GOLDEN-SPOTTED OAK BORER

Eliminating these pests may be impossible, but some remedies have succeeded in limiting the damage.

McDonough of The Arboretum notes that preventive chemical spraying has shown some positive results but is expensive and only feasible if the tree has significant economic value.

Entomologists Rugman-Jones and Stouthamer and Mark Hoddle, head of the Center of Invasive Species Research at UC Riverside, state that certain biological remedies, such as parasitoid wasps from the invasive pests’ native regions, have been effective in controlling Eucalyptus longhorned borers, lerp psyllids and ash whiteflies. Other possible regimens include nematodes, parasitic flies and helpful fungi.

However, so far nothing has been found that can undo harm already inflicted. Once a tree has been severely hit, it’s probably a goner.

The expected long-term consequences of this gigantic die-off are dire – less shade, less beauty, less wildlife habitat, less carbon and pollutants removed from the air.

“If we cannot control the shot hole borer, it will kill all the sycamores in California,” says UC Riverside’s Eskalen. And according to Hoddle, “there will be no miraculous recovery of these urban ecosystems after the beetles are done with them.”

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http://www.latimes.com/local/california/la-me-santa-monica-mountains-trees20171205-story.html

Drought and bugs have killed tens of thousands of trees in the Santa Monica Mountains

By Louis Sahagan

DEC 05, 2017

When biologist Rosi Dagit wants to give people a glimpse of 

the urgency of the problem afflicting trees in the Santa 

Monica Mountains, she takes them to a withering oasis in 

Topanga Canyon where hundreds of sycamores, alders and 
willows are dead and dying.

During a tour on Friday, Dagit saw damage almost everywhere she looked. 

Willows had lost their leaves from a fungal pathogen that coated their boughs with

 a crusty white residue. Sycamores and alders were splotched with half-dollar-size 

lesions caused by tiny beetles. Native shrubs were giving way to weeds.

Just six years ago, the creek offered all the arboreal comforts needed for frogs, newts and protected fish such Arroyo chubs and steelhead trout to avoid extinction: leafy canopies to control water temperature and prevent algae blooms, and willows buzzing with insects for nourishment.

Now, streamside trees weakened by drought are being ravaged by fungal diseases and swarms of insects the size of sesame seeds — imperiling not only the lush canopy but all the creatures that live in the stream.

"The ecological consequences of losing all these trees are profound and, on a personal level, so sad," said Dagit, a senior biologist for the Resource Conservation District of the Santa Monica Mountains.

New surveys of the 154,000-acre Santa Monica Mountains National Recreation Area conducted by remote sensing instruments on NASA aircraft and teams on the ground revealed a loss of about 9,100 — or 6% — of coast live oaks, and 114,000 — or 32% — of riparian trees including sycamores, alders and willows during five years of severe drought that ended in 2017. About 38% of the area's chaparral also died, NASA scientists said.

Ripple effects on the environment may already be underway. For example, mayflies, which float on the surface and are an easily accessible food for fish and frogs, have been replaced by tiny chironomid midges, which spend much of their lives hiding in sunken leaves. Whether Topanga Canyon's fish and frogs adapt to the shift remains to be seen, scientists say.

Dying trees and shrubs have exacerbated the plight of Western pond turtles, California's only native freshwater turtle. "The roughly 200 pond turtles left in the Santa Monicas eat and reproduce in water, and spend much of their lives hunkered down in chaparral and leaf litter," Dagit said. "With fewer places for them to hide from predators like raccoons and ravens, we're finding more and more pond turtles with their eyes pecked out and missing legs."

"We'll have to wait and see how it all plays out," Dagit said, shaking her head. "But I never thought I'd be witnessing the possible extinction of so many plants and animals in this area."

The magnitude of the devastation hit home as researchers including Dagit and a small army of volunteers began studying the results of the surveys of the Santa Monica Mountains National Recreation Area's matrix of public and private lands.

A summary of those findings will be presented Tuesday night at the Topanga Library in Topanga.

The data, which also came from the catch basins of more than 46 traps baited with chemical lures to attract insect pests, indicated that the hardest-hit areas were riparian zones where trees help control the environment of the canyon bottoms, creek flows and ponds they overhang and surround.

The native trees of the Santa Monica Mountains adapted over thousands of years to prolonged dry periods of drought. But aerial surveys using instruments designed to measure infrared radiation levels emitted by living and dead vegetation determined that the scale of the tree die-off was unprecedented in modern history, scientists said.

In addition, tree mortality rates were highest in areas that had the most number of days with temperatures exceeding 95 degrees, and the least number of days with rainfall.

Those conditions lowered water tables in canyon lands and deprived waterways such as Topanga Creek and Malibu Creek in the southern portions of the Santa Monica Mountains of historic flows, Natasha Stavros, an applied science systems engineer at NASA's Jet Propulsion Laboratory, said.

"Good rains like we had last year will not be enough to recover many of the losses we've seen," Stavros said. "That's because trees that have struggled through five years of drought depleted their natural defenses and resources, inviting fatal infestations of bugs and disease."

Still, Dagit found reason for hope in a clump of green willow saplings pushing up through the creek's muddy banks, about 30 feet from a water level gauge installed in the 1930s that was left high and dry in 2011 by diminished flows.

"Fish need trees," Dagit said.

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http://www.laalmanac.com/weather/we13.php

Total Seasonal Rainfall (Precipitation) averages 15 inches;
Downtown Los Angeles, 1877-2018

FOR THE PERIOD 1998-2018---11 INCHES(FOR THE PAST 7 YEARS-9 INCHES)

1988-1997 Downtown L.A. rainfall(inches)-14
1988-9 inches
1989-20
1990-18
1991-4
1992-16
1993-9
1994-37
1995-14
1996-3
1997-14
--------------------------
1978-1987 Annual L.A. DOWNTOWN L.A RAINFALL(INCHES)
16 INCHES ANNUALLY