Experts Not Definitive About Diagnosis of Weakening Oaks

By Christopher Jones

SOME TREES, such as this one planted outside Sfizi Cafe on the corner of West Broad and Oak St, have been healthy enough to hold their leaves through the winter, according to City of Falls Church Arborist Kate Reich. (Photo: Christopher Jones).

With native oak trees appearing unseasonably ill and eventually dying off, speculation that a disease spreading throughout the region could be infiltrating Falls Church abounded. But despite a troubling eye test from residents, local experts have yet to reach the same conclusion.

“It was heartbreaking!” said area resident Allison Dobbins about the loss of the massive oak tree in her front yard in the Poplar Heights neighborhood, just outside the City of Falls Church. One day, she said the massive tree had vitality, and then, “the very next day, it just wasn’t — it was completely dead and had to come down.” Soon after, a commercial arborist determined another mature oak in the front yard would have to be removed.

The cost: thousands of dollars, according to Dobbins. And, the tree die-off seemed to be spreading, block to block. “All of a sudden it pops up on trees in the neighborhood. They look like fall trees in the summertime, while all the other trees are alive and well,” said Dobbins. Has Oak Decline, a tree disease caused by the pathogen phytophthora, come to the City of Falls Church?

Not yet, according to Kate Reich, City of Falls Church arborist and Charles Prince, Falls Church Urban Forester, though they have seen significant oak tree problems just next door in Arlington County, where, per Reich, oak decline was pretty scary looking. Shannon Shy, consulting arborist with Ax Tree Services serving Falls Church and arborist for the Town of Vienna, said cases have been confirmed in Prince William County and parts of Maryland, but not yet in Falls Church City.

To explain why oak decline has hit Arlington County and not yet the City of Falls Church, Reich highlighted faster urbanization causing tree stress in the county. “Arlington is more urbanized than we are…,” she said, “and, we’re less paved than Arlington.”

For Reich and Prince, the oak tree die-off is explained, not simply by one particular tree fungus, bacteria or pest, but from a complex set of variables associated with a much wider array of causes, from climate and weather stresses (drought and excessive rain) to damaged root systems, poor soil structure, improper tree care and maintenance. Recent droughts in the area have particularly exacerbated the problem. “Historically, Northern Virginia doesn’t have a drought season,” Reich said, “But, we’ve been seeing a lot of drought. In fact, this last summer, the National Weather Service called it a ‘flash drought.’ I have never heard of that in my life,” she said.

Even though major oak decline hasn’t yet exploded in the City, Reich indicated many red oaks have suffered from bacterial leaf scorch.

Analysis of trees along West Broad Street has found that the trees in the median with higher soil volume at the base are faring better than the trees along the sidewalks in the smaller planter areas. Some trees near the Giant Foods at West Falls Plaza shopping center have suffered significantly and have required more pruning than usual.

“It is quite possible that once it’s run its course and killed a lot of red oaks, it’ll pick something else,” Reich said.

BUT OTHERS, such as Allison Dobbins’ dead oak tree in the Poplar Heights neighborhood in greater Falls Church, has been enough evidence for residents to conclude that something is amiss with the local crop. (Photo: Christopher Jones)

Aware of local concerns about oak decline, Reich and Prince would like to “combat misinformation” about the syndrome and help residents properly care for their trees. They’ve posted a new flyer on the Falls Church City government’s website entitled: “Oak Decline in Northern Virginia.”

“In recent years,” in northern Virginia, it begins, “oaks in the white oak group… have started dying in significant numbers. Some reports indicate other oaks are affected as well.” The die-off is caused by “water stress ” as well as “construction damage” on or “near your property.”

Homeowners can take a variety of steps to mitigate risks to their trees, including working with an International Society of Arboriculture (ISA) certified arborist who is “not associated with a tree service company” for guidance on tree and root damage prevention.

Within the City of Falls Church, tree care contractors are required to have an annual permit, according to Reich and Prince, and the City will provide homeowners a list of all tree companies who employ ISA Certified contractors.

According to Reich and Prince, mounding up a large pile of mulch in the shape of a volcano against the base of a tree’s trunk (i.e., “volcano mulch”) is one of the worst things a homeowner or tree service can do, because it risks rotting the tree’s root and bark systems, and can often kill a tree. The flyer also suggests giving trees “space” by considering replacing grassy lawn areas surrounding the base of the tree with mulched and shrubbed zones (since the roots of grasses run deep and compete for nutrients with the trees’ roots.)

Being sure to have proper soil tests before applying potentially “unnecessary” or harmful fertilizers or sprays is also important.

The flyer places special emphasis on avoiding treating “diseases or insects without knowing the cause of [a tree’s] decline,” since “treating for diseases that are not present or treating when it will not help the tree’s likelihood of survival will waste your money and can cause negative impacts to our local ecosystems.”

They also list five “Secondary Factors” identified by tree specialists as causing “stressed trees,” for which treatments are not likely to “improve your tree’s health.” These include: Armillaria root rot, Hypoxylon Canker, Ambrosia Beetles, Bacterial Leaf Scorch, and Two-Lined Chestnut Borer. The flyer also provides many helpful links for the homeowner concerned about tree care.

For Reich and Prince, who oversee and protect the City’s inventory of 10,000 trees, vigilance is essential. “Falls Church has a tree culture and we want to support that,” Reich reassured.