TREE TIPS
TREE & SHRUB CARE FROM BARTLETT TREE EXPERTS
Mulch to Improve
Tree Health by Tom Smiley Ph.D.
Mulching the soil surface around your trees
and shrubs in one of the best treatments you
can provide to increase root development and
improve tree health. Numerous studies over
decades have shown that maintaining a 2 to 4
inch layer of mulch will conserve soil moisture,
reduce compaction, increase nutrient levels
and moderate soil temperatures. Mulch beds
can look good and reduce lawn mowing time.
Root density is
increased under mulch,
as shown in this photo
by Dr. G. Watson.
Grass
Mulch
One of the best materials to use as a mulch
is fresh wood chips. Wood chips contain bark,
leaves and wood. Because of this mixture,
more nutrient are available to the tree. In many
areas, a 4 inch layer of wood chips applied in
late winter or early spring will decompose to
one inch or less by fall. The decomposing chips
will work their way into the soil, which will help
reduce soil compaction.
Whether you have wood chips, other mulches
or ground cover plants growing under your
trees, be sure to keep them off of the trunk and
buttress roots. When against the trunk, any of
these can keep moisture levels high on the bark
and promote some fungal pathogens. They can
also hide the fruiting structures of root decay
fungi. So keep ground cover plants at least a
foot away from tree trunks.
Your Arborist Representative may be able
to provide you with fresh wood chips. Contact
him/her for more information.
The Importance of
Soil Nutrient Analysis and Prescription
Most people know that plants perform best
when supplied with nutrients such as nitrogen,
phosphorous, and potassium. However, what is
often overlooked is that these nutrients, when
applied in excessive quantities or inappropriate
forms can actually cause unintended negative
consequences to the environment, particularly
water resources. In fact, phosphorous is one of
the most damaging pollutants of freshwater
and marine ecosystems, and is almost always
present in soil in ample quantities. This is
why most Bartlett regional fertilizer blends
are predominantly phosphorous-free; because
hundreds of soil samples taken by Bartlett
Arborists have shown that in most regions of
North America, adding phosphorous is not needed.
Bartlett fertilizer blends also use a slow release
nitrogen source, ensuring that the nutrient stays
in the root zone available for plant uptake,
rather than leaching through the soil into the
water table.
In addition to the so-called ‘macro’-nutrients
(nitrogen, phosphorous, potassium) which are
present in most over-the-counter fertilizer
blends, ‘micro’-nutrients such as calcium,
magnesium, manganese, and iron play a
critical role in growth, photosynthesis, and
defense against disease and insect problems.
Calcium, for example, is an integral
Rhododendron leaves showing classic ‘interveinal
chlorosis’ indicates an iron deficiency; likely due to
high pH or excessive phosphorous, or both.
You can see the difference compared
to the healthy leaves below.
by Drew Zwart Ph.D.
component of cell wall strength, and plants that
are lacking calcium are more susceptible to
root rot diseases and leaf chewing insects. Iron
plays a major role in photosynthesis, and is often
deficient in leaf tissue even though there is ample
iron in the soil. This is because the pH of the
soil (acidity or alkalinity) can influence nutrient
availability. At high pH values (above neutral
7), iron is unavailable for uptake, while at more
acidic soil pH (4.5-6.5), it is readily available.
Often an iron deficiency is actually a pH issue.
Any fertilization should be done based on the
results of a soil nutrient analysis, and the ideal
fertilizer is a custom blend specific to the soils in
question and the plants growing there. Fertilizer
should be added to meet the plant needs, adjust
pH issues, and correct deficiencies, without
over applying nutrients that may end up in the
water rather than the plant. Not all fertilizers
are created equal, and a blend prescribed
based on specific soil and plants present on
site will result in maximum benefit and minimal
environmental impact.
Pest Alert-
Bark Beetles by Drew Zwart Ph.D.
Bad times for trees lead to good times for beetles
In recent years, Bartlett arborists throughout
the west have seen an uptick in the number of
beetle pests attacking trees, often leading to
tree mortality. There are several causes for this
increase, and unfortunately these causes are likely
to become increasingly common in the future.
Introduction from afar
One reason bark beetle
and other beetle attacks
in trees are on the
rise is the continuous
introduction of new
species from other
regions of the world.
Generally speaking,
native plants and insects
that have evolved
together tend to coexist
in a balance that favors
Bronze birch beetle damage neither the pest nor the
under tree bark.
plant. Tree defenses
have evolved to protect against attack, leaving
only stressed trees with compromised defenses
susceptible to insect attack and successful
breeding. Examples of introduced beetles include
the bronze birch borer killing birches from
California through the Pacific Northwest, and gold
spotted oak borers and polyphagous shot hole
borer (detailed on page 3) killing many trees in
southern California.
Stressful times
Trees under stressful environmental conditions
release a number of gaseous alcohols, many
of which such as ethanol are known to attract
beetle attacks. Once a tree has been successfully
colonized, beetles will also release a ‘mass attack’
hormone, indicating to other individuals that a
suitable breeding tree has been
located. When this occurs, both
the infested tree and nearby trees
are rapidly attacked by thousands
more beetles, leading from stress
to death. Drought stress is often
the trigger for these attacks, as is
the case with the native Western
oak bark beetle in California, Ips
engraver beetles of pine in Arizona
and Southern California, and many
others. Poor soil conditions like
compaction, nutrient deficiencies,
or water-logging will also trigger
ethanol production.
This pine has been attacked by
Ips engraver beetles
The things they carry
In many cases, the fungi that bark beetles carry
with them are more damaging to trees than the
beetle itself. Most bark and ambrosia beetles have
specialized structures called ‘mycangia’ that have
evolved to carry spores from one tree to the next.
The fungi serve as food for the developing larvae,
and emerging adults carry the spores to the
next tree. “Thousand Cankers Disease”, a lethal
condition found in walnut from California through
Oregon and Washington is a prime example
caused by the combination of the Walnut twig
beetle carrying the pathogenic fungus Geosmithia
morbida. Other examples include blue stain fungi
carried by Ips engraver beetles to pines in Arizona
and elsewhere, the Fusarium fungus carried by
the Polyphagous shot hole borer to many hosts,
and the ‘foamy canker’ fungus (Geosmithia
pallida) carried by the Western oak bark beetle in
California.
The best management practice for these pests
is to avoid physiological stress, which is falls
These two examples
show branch cankers
around twig beetle
galleries (above) and
staining in wood caused
by a beetle-introduced
fungus.
firmly in the category of ‘easier said than done’.
Practices such as mulching, irrigating during
dry stretches, and amending soil according
to nutrient analyses can reduce stress, while
protective bark applications can reduce or
eliminate successful attacks of stressed trees.
Some (but not all) beetles can also be managed
with systemic insecticides, but this does not
always help when the major damage is caused
by the fungal associate. Overall, management
will require a multifaceted approach based
on knowledge of hosts, local pests, and
environmental conditions.
Photo Credits: Attack on birch by Steven Katovich, USDA Forest Service;
Birch borer beetle by Whitney Cranshaw, Colorado State University;
Attack on pine by Chris Schnepf, University of Idaho; Branch cankers
by Ned Tisserat, Colorado State University; all from Bugwood.org
Tree Focus-
Red Yucca (Hesperaloe parviflora)
Hesperaloe parvifolia or Red Yucca is actually not a yucca at
all. The Texas native has an evergreen, spiky appearance and
growing habit similar of a yucca but yields a surprise in its
wonderful pink to reddish like blooms from mid spring into early
summer. These showy flowers are great pollinator attractors and
a favorite of our hummingbirds here at the Research Laboratory
and Arboretum.
Book Reviews
Understanding Tree Law
by Barri Bonapart
Polyphagous
Shot Hole Borer Update
Blue palo verde trees such as these are
among the many native trees attacked by the
polyphagus hole shot borer.
by Drew Zwart Ph.D.
The polyphagous shot hole borer (PSHB,
Euwellacea sp.) is a recently introduced,
non-native beetle that is having devastating
effects on landscapes, forests, and agriculture
in southern California. The pest is especially
damaging because it introduces a pathogenic
fungus (Fusarium euwallacea) which rapidly kills
trees. This pest has dozens of host plants that are
broken down into three categories:
 N on-hosts: beetle attacks the plant and is
repelled without fungal introduction
 F ungal hosts: beetle introduces the lethal
fungus, but does not reproduce
 True hosts: beetle introduces the lethal fungus
and reproduces successfully
Management options for this insect/pathogen
combination are currently being researched
by several entities, including scientists in the
University of California system and Bartlett Tree
Research Labs (west). So far, several fungicides
have been shown to impede the pathogen in
culture, but field trials in trees have been less
successful. Systemic insecticides may kill
the beetle and its larvae, but do not prevent
introduction of the lethal pathogen. Combinations
of fungicides and insecticides are currently being
investigated, but, to date there are no registered
options aside from protective bark applications,
which are not 100% effective.
True hosts are plentiful in landscape plantings,
and include many native trees such as Coast,
Valley, and Englemann oaks, Sycamore, Big-leaf
maple, boxelder, and blue palo verde. Non-native
Telltale signs are multiple small
holes surrounded by white crust,
and/or wet bark
true hosts common in the landscape include
several other oak and maple species, avocado,
coral tree, camellia, acacia, and many others.
Signs of PSHB attack include multiple small holes
often surrounded by white crust, wet bark, or both.
Informative App for
Urban Tree Identification
City Tree is an iPhone app from leading botanist, Dr. Matt
Ritter. This easy-to-use app helps to quickly identify any
city tree. Learn over 300 of the world’s most common urban
trees. Browse, identify, explore, share. This app is made and
reviewed by university professors and tree experts and has
over 600 high quality images and drawings.
The City Tree app for iPhone
is available on iTunes ($3.99).
A treatise that is
both informative and
entertaining, this book
is the first in-depth
treatment of this
often contentious and
confusing area of
law. Written by the
country’s leading
expert in the litigation
and mediation of tree and
neighbor disputes, it provides practitioners with a
comprehensive explanation of all aspects of tree
law, including view obstructions, damage from
falling trees and limbs, nuisance from hazards,
debris and roots, injury from tree failures,
ownership versus encroachment, trespass and
wrongful cutting of trees, and appraisal of trees
that have been damaged or removed. Because
it’s never about the trees, the author reveals
an insider’s perspective on tips and strategies
for resolving clients’ matters by identifying,
understanding, and defusing the psychological
underpinnings that often plague these disputes.
Pacific Coast
Tree Finder: A
Pocket Manual for
Identifying Pacific
Coast Trees
by Tom Watts
The classic key to identifying native trees of
the Pacific Coast, updated to reflect changes in
the names of trees since publication of the first
edition. Identifies native trees, and some widely
introduced or naturalized species, of the Pacific
Coast region, from British Columbia to Baja
California. In this edition, Latin names of trees
that grow in California conform to the University
of California’s 1993 Jepson Manual, and more
recent name changes. From the Finders series of
pocket guides to native plants and animals of
the U.S. and Canada; like all plant guides in the
series, this book uses a dichotomous key format
for accurate identification.
No Paper - No Problem!
Its easy to enroll in our paperless program for
electronic Tree Tips. Find your 7-digit client code
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www.bartlett.com/newsletter (select US), click on
the registration link and sign up using your client
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service again, just advise us.
Compliments of
TREE TIPS
This issue will help you
understand Spring treatments.
Please call me if you have any
concerns with your property.
LAB NOTES
Utilizing Molecular Tests to Aid in Diagnostics
by Andrew Loyd
Recently, the Bartlett Diagnostic Laboratory
purchased new equipment that will allow us to
conduct molecular analyses, which will enhance
our diagnostic ability. Some microorganisms
(especially ones that cannot grow in culture)
require molecular-based tests for confirmation,
such as the phytoplasmas that infect palms, ash,
juniper, and elm. Using these molecular methods,
we will be able to confidently confirm and validate
diagnoses to the genus and species level.
which tells us the exact composition for that
segment of the targeted gene. The sequence
will be a unique series of nucleotides (building
blocks of DNA), which can act like a barcode. We
can search extensive DNA libraries for series of
nucleotides that match our unknown, revealing
the organism’s identity. Several databases
exist, some specific and some generic, but all
are curated and contributed to by the scientific
community.
We will use conventional PCR (polymerase chain
reaction) and DNA sequencing to identify unknown
fungi, bacteria, nematodes, insects, and some
viruses. Conventional PCR makes millions of
copies of a piece of a gene from an unknown
organism. The PCR product is then sequenced,
From a diagnostic standpoint, molecular methods
are yet another great tool for us to accurately
identify the possible cause of a plant problem.
As our world and
© 2015 The F. A. Bartlett Tree Expert Company
DNA
sequencing
allows Bartlett
scientists to
diagnose more
tree problems.
work become more scientifically driven, it is
important to keep up with the latest developments,
and this upgrade of our lab’s capabilities will allow
us to provide our clients with the most advanced
diagnostic services in the industry.
published by THE F. A. BARTLETT TREE EXPERT COMPANY
(877) BARTLETT (877-227-8538) in U.S. and Canada • www.bartlett.com
For Tree Tips information contact [email protected]
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