Mysterious Willow Die-Off at Escondido Creek

A mysterious pest has damaged willows along the Escondido Creek Watershed, leaving conservation officials scrambling for answers to the die-off.

Officials with the Escondido Creek Conservancy originally feared the damage was caused by the shot hole borer beetle, which attacks 137 tree species including willows, oaks and sycamores.

Tests at UC Riverside came back negative for a fungus associated with the beetle, but didn’t reveal what could be threatening the watershed.

“.. It was found to not be the beetle — it was something else going on,” said Ann Van Leer, executive director of the conservancy.

The problem began over the summer, when the Escondido Creek Conservancy learned that trees in Elfin Forest were rapidly wilting and dying, Van Leer said. Months later, the damage is especially visible near Questhaven and Harmony Grove Road — a spot that conservancy board member Leonard Wittwer called “ground zero”of the infestation — where a tangled heap of branches lies in the creek bed. Blackened leaves droop from nearby trees.

“When these things became infested, it was like someone turned their blow torch on and burned them,” Wittwer said.

On Aug. 3, the conservancy closed the trails in the Los Cielos Preserve, out of fear that the invasive beetles could be causing the destruction.

The Kuroshio Shot Hole Borer has infested areas of coastal San Diego, according to the University of California Division of Agriculture and Natural Resources. The insect, an invasive species that originates from the highlands of Taiwan and Okinawa, decimated the Tijuana River Valley, where hundreds of thousands of denuded tree trunks stand in the place of formerly lush streamside habitat.

The collapse of willow groves ripples through the watershed’s ecosystem, Van Leer said.

“Willows are one of the key trees which support other plants and animals,” she said. “It’s one of the foundation plants. A lot of birds and insects rely on the willows. It’s an indicator species of the watershed.”

The loss of those trees harms animals such as the least Bell’s vireo, an endangered songbird that lives along streams. And the stands of dead wood pose their own hazards to surrounding communities.

“It’s an ecological bummer and then becomes a fire hazard,” Wittwer said.

Worried that Escondido Creek could suffer similar damage, the conservancy closed its trails to the public on Aug. 3, and submitted samples from the trees to plant pathologist Akif Eskalen at UC Riverside.

“We didn’t know, and we wanted to be very cautious, because we didn’t want people and bicycles spreading the infection by moving through the area,” Van Leer said. 

They were surprised but relieved to find that the samples showed no signs of Fusarium fungus, which transports and spreads the beetle infestation. Instead, the lab found a different fungus, Phaeoacremonium.

The results only compounded the puzzle, however, since Phaeoacremonium is a slow-growing pest that isn’t associated with sudden die-offs.

“In communications with Dr. Eskalen, he was interested as to why our willows trees have died so quickly from this particular fungus, which is known to slowly kill trees,” the conservancy stated on its website. “He wondered if something else may additionally be affecting these willows.”

Eskalen said he plans to visit the site on December 2, and hopes to get additional clues to the die-off.

"This is a new disease that we haven’t figured out yet," he said. "We still don’t know what caused the decline of those willows."

After learning that the trees tested negative for the invasive beetles, the conservancy reopened the trails at Los Cielos. They’re also looking for ways to help boost the trees’ resistance to the fungus, and plan to watch carefully for signs of renewed die-off next spring. In the meantime, officials urge hikers and cyclists to stay on the trails, keep dogs on leash, and never remove firewood from the preserve.

View images, video and full article

Reporter: Deborah Brennan

Photographer: Peggy Peattie

Editor: Misael Virgen

December Work Parties

Planting Has Commenced!

With the help of our volunteers, this month the DDHPL has planted hundreds of new natives. Rather than digging holes for each new plant, the recent rains have made the ground pliable enough to pound in each pole cutting with a 3 pound sledge hammer. 

Dec. 3-4: "Thanks to the efforts of local volunteers and our friends from Solana Beach Eco-Rotarians, the Del Dios Habitat Protection League's efforts to restore our native environment was bolstered by the planting of 250 natives!"  
- Stan Alstrum

Dec. 10-11: 200 Pole cuttings of mulefat were planted at Green Lagoon on Saturday and more poles collected on Sunday for planting the following week.

Dec. 18th: A group of our local teen volunteers hammered in 300 plants - bringing the total for this group to 750! Go Teens!!

The "Mulefat Chain Gang" earned their name by planting 300 pole cuttings in a single day!

The "Mulefat Chain Gang" earned their name by planting 300 pole cuttings in a single day!

Win This Firewood!

Firewood Raffle

We have a winner!

Our first annual firewood raffle winner is DDHPL Member, Chris Chandler. Congratulations Chris!! The drawing was help at the CDel Dios Mt Isreal Community Holiday Potluck with the winning ticket pulled by the Citizen of the Year - Mitch the Hodgee Carver. A big thank you to everyone who bought raffle tickets and supported the DDHPL. 

Interested in firewood or participating in future drawings? Subscribe to our newsletter to receive updates on projects and events. 

If you haven't become a Member of the DDHPL yet, pop on over to our Membership page & join today!

Project Update - December

Oak Woodland Restoration and Fire Fuel Reduction Project Update

December 2016

Invasive removal is focused on tamarisk and pampas grass. These invasive plants are being sprayed or removed, around the lake perimeter. December work will include eucalyptus removal. Roadside weeds were sprayed in November to help with next year’s fire season.

Planting has begun - 250 plants were planted by volunteers on 12/3 and a good time was had by all. Locally harvested mulefat and willow were planted, and more pole planting is happening thru January. Its a great way to actively connect with nature, so kids absolutely love it. 

Stinkwort- Update: 9 locations were found and removed in our community of Del Dios. Volunteers cruised the streets, and we think we found all weed populations and removed them. We will be monitoring in July 2017 to where this new invasive shows up in town.

Volunteer days start with the promise of cooler weather,  I Love a Clean San Diego brought 80 volunteers, removing 40 pounds of garbage and 2 full dumpster loads of tamarisk.   (See Photos Here) 

The natives plantings are coming in strong in our restoration areas, however , please stay out of the Restoration Areas except for volunteering at Del Dios Habitat Protection League events.