I have been getting an increased number of calls from people concerned about their tree(s) starting to dieback. They want a certified or registered consulting arborist to evaluate the tree health condition, determine the cause of the tree decline, and recommend treatment options or removal.
For the past two to three years, I have noticed the increasing number of declining trees throughout San Diego. Especially noticeable is the tree dieback in the backcountry as well as local canyons and open spaces. Even drought tolerant Eucalyptus, Oak and Pines trees are struggling to survive.
The cause of our tree decline and dieback is the ongoing California drought. With yet another year of little winter rain, soils throughout San Diego county have little moisture reserve remaining. The drought is affecting native as well as ornamental trees used in the landscape.
Indeed, certain trees in our area are struggling due to insect infestation. The gold spotted oak borer attacking Coast Live Oak, as well as a host of ornamentals including Olive and Liquidambar trees have been infected with fusarium vascular disease introduced from borer and insect infestations. Therefore, it is not uncommon for most people to assume their tree must be declining due to some kind of insect or disease.
I have observed people rarely consider the effect of the drought as being the primary cause for tree decline. The tree living in the back yard or slope area for the past several decades may be dying simply because there is no more water in the soil profile! Even the deepest rooted trees cannot survive accumulated years of consecutive drought.
I recently received a call from a gentleman complaining his fifty year old Jacaranda tree was dying. The new foliage had germinated then died back, now small twigs and branches were dropping. The bark on the trunk was exhibiting uncharacteristic roughening. The tree was located at the bottom of a slope near a turf area. Months ago, the turf sprinklers had been turned off, now the tree was struggling to survive.
Tree roots seeking moisture grow well beyond the drip line of the tree crown. Under drought conditions, soil moisture is not being recharged from winter rains. Unless a tree is receiving supplemental irrigation, it is reliant upon finding soil moisture by growing into irrigated turf and planter areas.
With increased water restrictions and rates, people are reducing or eliminating irrigation to their lawns and shrub beds without considering the effect on nearby trees. Trees that adapted their root systems to getting water from nearby irrigated areas that no longer get watered will begin to decline as the remaining soil moisture is exhausted.
A tree weakened by drought becomes increasingly susceptible to secondary pest or disease infestations. Many beetles can detect stressed trees from miles away. However, attempts to eradicate secondary insect infestations will not resolve the underlying cause of the tree decline.
So, if you notice your tree starting to decline, here is a brief check list of considerations:
-Is the tree irrigated or non-irrigated?
-If non-irrigated, does the tree get water from a nearby irrigated source?
-Has there been recent re-programming or turning off the irrigation?
-Any recent construction or trenching nearby the tree?
-Any grade change such as fill soils placed over the tree roots or cuts?
A well maintained, mature street tree in the front yard of a property may add an additional 7% to the assessed value of a property, a dead or declining tree obviously reduces street appeal and real estate value. Trees can be retained and successfully survive the ongoing drought, contact a certified or registered consulting arborist to provide a tree health evaluation and recommendations on how to protect your tree investment value.