Since the early 1900s, eucalyptus trees have been a staple member of Rancho Santa Fe’s ecological landscape. Unfortunately, years of drought and invasive parasites have proven to be tough challenges for the RSF Association Parks and Recreation Department. Nevertheless, the outlook for other varieties of the Ranch’s signature eucalyptus is positive.
RSF Parks and Recreation Manager, Arnold Keene presented an update at the latest Board meeting on what the department has been doing to save the Ranch’s Red Gum Eucalyptus trees as well as others in the Ranch.
“Trees are one of the most valuable assets to our community…and the condition of some trees are very poor,” Keene explained.
As many in the community are aware, Lerp Psyllid, a pest that feeds almost exclusively on Red Gum Eucalyptus was discovered in the Ranch in 2000. Since then, efforts to rid Lerp Psyllid have not come as far as many would like. The pest is now a fixture in the Ranch’s ecology, Keene explained.
A few years after the discovery of Lerp Psyllid a professor from UC Berkeley introduced a parasitic wasp to attack the Lerp Psyllid and this proved to be a good biological control, Keene said.
“However, there now seems to be a balance that goes back and forth between the two. The wasp will gain ground and then loses its food supply and the Lerp Psyllid will reappear,” he added.
Keene expounded that at first, there were maybe two to three cycles of this a year, but now there are about five to six.
“When the trees are struggling it becomes opportunistic for other insects…Lerp Psyllid doesn’t actually kill the trees but only weakens them. Other insects then come in and kill the trees.” He added, “In addition, five years of drought have not helped the trees recover.”
The Red Gum Eucalyptus is not the only tree being attacked. Keene explained that the pine beetle is killing off pine trees at a rapid pace.
“It is a very quick kill off. There will be a small brown patch on the tree and two to three weeks later the tree will die,” he said.
There have been mixed results on chemical applications to kill any of these insects.
“It is not a sure thing because the chemicals will kill some of the birds and the parasitic wasps as well, so you want to be careful when you use some of these chemicals on these trees,” Keene explained
He further added that the Ranch has too many trees competing for very limited resources. “Our biggest goal is figuring out how to adapt to a changing water culture.”
Tree management going forward will continue to identify dead and dying trees. They will continue to work education and training efforts in the community with the Fire Department and the CONE Committee.
“We are trying to get the word out on how to maintain trees. We are always available to visit individual properties to examine trees,” said Keene.
For the trees that fell down during the recent windstorm, the department is working toward clearing them. All of the roads are open and the department is now helping clear trees that knocked down fences, gates, and walls on two properties. Thankfully, no one was injured.
It is imperative that individual households contact the Fire Department or Parks and Recreation to clear dying and dangerous trees. “Overall, the trees are in good condition,” Keene concluded.