Moths Prolific, But Not Worrisome Says Parks Director

They may not be as noisy the 17-year cicadas that have taken up residence across in backyards and parks across the eastern U.S., but the small brown moths that are suddenly prolific in Belmont yards and in open space areas are invasive nonetheless.

Several Patch readers have inquired about these unexpected visitors, so we've reached out to Belmont Parks & Recreation Director Jonathan Gervais for some answers. Gervais explained a bit about the California oak moth ((Phryganidia californica), and the effect of these moths on oak trees. 

The California oak moth (Phryganidia californica) is a native insect of coastal California. The caterpillars feed upon the leaves of our native Coast Live Oak and also some deciduous trees.
 
During these outbreaks caterpillars are often seen suspended from silk strands, dropping to the ground, and congregating on fence posts, mail boxes, and other available platforms. In the most extreme years, the infestation may lead to severe oak defoliation.  

The tan brown adult moths are seen in the late afternoons as they hover around infested trees with the goal of mating and laying eggs for the next generation of caterpillars. Larger outbreaks occur approximately every 8-10 years.  

Healthy oaks usually recover from these defoliation events. Age, condition of trees, as well as human caused impacts are also factors in how well oaks recover.  

Oaks that are simultaneously subjected to stresses caused by landscape or home construction, drought, soil compaction, or fungal infections (i.e. Sudden Oak Death Syndrome or oak root fungus) may be more seriously impacted. Gervais says the Parks and Recreation Department has been monitoring the situation but is not proposing action at this time.
 
"We are hesitant to spray insecticides in Belmont neighborhoods because of health concerns for the citizens and their pets," said Gervais.

"The permitting required for spraying these chemicals is also an issue.  In addition, this is a natural process that, although destructive, is part of the natural heritage of living in a wooded community," he added.

Residents concerned about a particular oak may wish to engage a certified arborist to evaluate the impact of the moths on an individual tree. Most trees will survive, but some may need additional help to make it through, according to Gervais.