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Integrated Pest Management (IPM)
This is a big buzzword among
gardeners and farmers. There are a lot of definitions of IPM
out there but here are the basic concepts:
- Put the right plant in the right place! Don’t
force something to grow under conditions it can’t handle.
FUF helps you with that decision when you plant through
us.
- Improve the cultural conditions. Cultural conditions
include water, light, pollution, wind and soil. Some conditions
are more controllable than others. See our pages about watering
and soil for more info.
- Know your pest. Is it a bug, disease, or abiotic
(not caused by a living thing)? Find out as much as possible
so your efforts aren’t wasted. The goal is not total
pest elimination, the goal is a reasonable number of pests
on an otherwise healthy plant. To follow is a list of the
most common pests.
- Choose the least toxic method of pest control.
Look at improving cultural conditions first, then try a
non-chemical method of control. Often these methods work.
Chemicals are a last resort.
- Know your chemical if you must use one. What specifically
does it kill? How do you use it? How long does it stay in
the soil or air? What are the risks to you or the environment
around you?
Use the links below to jump to different areas
of this page:
Abiotic Disorders
(not caused by a bug or disease)
- Water stress
- Windburn
- Nutrient Deficiency
- Frost Dieback
- Toxic Chemicals dumped into tree basin
The most common bugs
- Aphids -> Ants and Sooty Mold
- Scale
The most common diseases/ailments
- Chinese Elm Anthracnose
- Fireblight
- Powdery Mildew
- Shothole Fungus
- Sooty Mold
Other Pest Resources
Abiotic
Disorders (not caused by a bug or disease)
- Water stress – Signs of underwatering
may include low vigor, wilting or leaf drop, dieback (branches
die from the tip back) or very little new growth. It’s
easy to underwater in sandy and windy conditions. See our
watering section for more info.
- Signs of overwatering/poor soil drainage
may include the same symptoms as those of underwatering.
Leaves may appear yellowish. However, the soil may be swampy
or even smell bad. Usually found in soils with high clay
content.
- Nitrogen Deficiency – In sandy
soils, low nitrogen levels may cause leaves to appear yellowish,
or chlorotic. Adding organic nitrogen fertilizer on a regular
basis can help – but don’t overdo it. For a photo,
see this link:
www.ipm.ucdavis.edu/PMG/M/A-WO-MDEF-FO.016.html
- Iron deficiency – the leaves
will yellow, but the veins remain green. This is known as
iron chlorosis. Can be fatal on Italian Buckthorn (Rhamnus
alaternus). Treat by adding chelated iron to the soil as
per manufacturer’s instructions. For a photo, see this
link:
www.ipm.ucdavis.edu/PMG/M/A-WO-MDEF-FO.004.html
- Windburn – brown edges of leaves
especially leaf edges or sections that are thin or pointy.
The wind is very drying, so you could try increasing the
water if the soil is well-draining. Windburn is usually
not fatal if the tree is generally tolerant of conditions.
This is usually more noticed on young trees.
- Frost Dieback – In rare cases
of frost, some plants will partially or fully die back.
Many of our trees are native to mild coastal climates and
not tolerant of frost. The older the tree, the more likely
it is to survive. Don’t prune off the frost-burned
branches until you are sure no further frosts are expected.
The outer foliage is keeping the inner foliage warm. To
prevent frost burn, keep plants well watered. Cover with
an old sheet or towel at night if frost is expected, trying
to leave an air gap between the sheet and foliage. Uncover
during the day. Outdoor rated string lights ("Christmas
lights") in the tree at night can also help, especially
if it is covered. Jacaranda (Jacaranda mimosifolia) and
New Zealand Christmas trees (Metrosiderus excelsus) are
some of the more common San Francisco street trees subject
to frost damage.
- Chemicals dumped into tree basin –
This could include but is not limited to: painting chemicals,
motor oil, cleaning solvents, etc. Painting chemicals seem
to cause the most sudden and dramatic tree death when dumped
into tree basins. The leaves generally wilt and brown within
1-3 days and the tree does not recover. Other chemicals
may cause longer lasting declines. Be sure that any contractors
you hire understand that they are not to dump any toxins
in the tree basins (including the neighbor’s!) and
that they are responsible for the cost of removing and replacing
any trees that die if they do. They should replace the tree
at the size it was when it died, not the size it was when
it was planted. If you suspect chemical dump, gather some
soil with a trowel and smell it. You may detect a chemical
odor.
The most common bugs
Aphids-> Ants (and Sooty Mold)
Although sooty mold is not a bug, it is generally associated
with aphids
Aphids are among the most common garden
pests, especially in the spring and summer. It’s not
cause for panic, but you may want to control their population.
Here we describe the pests and their affects, and list some
least toxic methods of control. (Some text adapted from the
Department of the Environment website; see links below)
Identification
Aphids are small (less than 1/4
inch long), soft-bodied insects that suck sap from leaves,
twigs, or roots. They may be green, yellow, brown, red, or
black depending on the species and the plants they feed on.
They are pear-shaped insects with long legs and antennae.
Adult aphids can be winged or wingless. They are often clustered
on new growth.
Although aphids are most common in spring
and summer. some species mate and produce eggs in fall or
winter, which provides them a more hardy stage to survive
harsh weather. Under ideal temperatures, many aphid species
can complete their life cycle in less than 2 weeks, and because
of their prolific reproductive capacity, enormous populations
of aphids can build up in a short time.
Although aphids seldom kill a plant, the
damage and unsightly mold growth they cause sometimes warrant
control. Aphids cause curling, yellowing, and distortion of
leaves and stunting of shoots. Moreover, aphids serve as carriers
of viral diseases on certain vegetable and ornamental plants.
In urban environments, aphids can produce copious amounts
of honeydew, which often turns black with the growth of a
sooty mold fungus. Sooty mold is usually just unsightly, coating
leaves with a black residue, but can kill a small tree that
is already under stress.
Check plants frequently for aphids, including
the undersides of leaves. Look for curled green leaves and/or
wilted buds. Many species of aphids cause the greatest damage
when temperatures are cool (65-80 F). The presence of ants
often indicate aphids, because ants act as "farmers,"
protecting the aphids, in return for their "honeydew"
excretions.
Suggested steps for treating trees
for aphid infestations:
- First, is it a big deal? If there is little
damage, some aphids are o.k. Even in our urban environment,
aphids have natural predators. They will manage the problem,
keeping the population under control. We actually want some
aphids in order to sustain the predators so they can reproduce
to eat more aphids! The key here is not to panic if a few
aphids are feeding on a tree.
- The easiest thing to do is to wash off the
aphids with a strong jet of water one morning per week.
(morning is best, allowing the leaves to dry during the
day) Doing it more than once a week helps keep the population
down. You can wash leaves when you’re watering your
young tree, washing your car, or watering plants. If you
do not have access to a hose, use a compressed air or backpack
sprayer filled with water. (These can also be used to apply
the following recommended insecticides.)
- Control the ants, who protect the aphids.
Traps, such as Tanglefoot®, can be smeared on a stiff
band of paper taped around the trunk and stakes. Change
the Tanglefoot-coated paper if it gets covered by ants.
Otherwise they will use the dead ants as a bridge to get
to the aphids. Follow the manufacturer’s application
instrucions. Also, place it where pets or people will not
brush up against it. Inside-out duct tape will do a similar
job but it is weaker. And don’t leave anything on long
enough to strangle the tree!
- If aphids are causing sufficient damage to
warrant further treatment, or if washing with plain water
has not worked, we suggest one of two insecticides. Always
follow manufacturer’s application instructions:
a. Safer Insecticidal Soap - A contact
insecticide that is fully biodegradable. It works by smothering
rather than poisoning .
b. Bio-Neem by Safer or, Fruit, Nut, and Vegetable
or Rose Defense by Green Light : derived from the neem
plant, these products operate in several ways. Bio-Neem
acts more slowly than the Green Light products. It disrupts
the hormonal balance so aphids die before they molt to
the next life stage, suppresses the aphids' desire to
feed, and repels other insects. The Green Light products
(both are the same except for the name), work quickly
by suffocating the aphids. They also serve as a repellant
and a fungicide. To avoid harming beneficial insects,
apply the Green Light products during early morning or
late afternoon, times when honeybees are not active. Otherwise,
both do not effect beneficial insects, such as honeybees
and ladybugs. Local nurseries, such as Sloat Garden Center,
carry neem-based insecticides.
Scale
Scale insects are usually slow moving or don’t
move at all. They may look like little bumps clustered on
the plant. They are also often accompanied by ants. Their
honeydew excretions can also cause sooty mold. The black scales
are very common on Purple Hopseed (Dodonaea viscosa ‘Purpurea’)
or sometimes on Strawberry tree (Arbutus ‘Marina’).
However, there are many kinds of scale.
Treatment: use ant control measures as listed in the aphid
section (insert link here). Horticultural oils or soaps can
work if timed correctly. For more info, see this link
www.ipm.ucdavis.edu/PMG/S/I-HO-SOLE-AD.006.html
The most common diseases/ailments
Fireblight
Fireblight is a bacterial disease affecting plants in the
rose family such as pear, cherry and apple. It’s characterized
by branches looking black and wilted as if they have been
burned by fire. For more information, see this link: www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7414.html
Powdery Mildew
Powdery mildew appears as a fine white dusting on leaves,
causing leaves to look whitish and a bit rumpled. Powdery
mildew is caused by cool, damp, foggy weather, of which San
Francisco has plenty. Rain and direct sunlight inhibit powdery
mildew. Often seen on London plane/sycamore trees in the city
(Platanus acerifolia), it is generally cosmetic and not fatal.
The ‘Yarwood’ variety of sycamore is more resistant.
For a photo and more info, see this link: www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7493.html
Take control measures on highly susceptible
species such as roses, crape myrtle and euonymous. Prune out
infected tissue and dispose of it away from plants. Do not
prune during dry weather and avoid excessive fertilization
or irrigation – these promote susceptible new growth.
Overhead sprinkling may reduce powdery mildew infection because
spores cannot germinate, and some are killed, when plants
are wet. Sprinkle plants in the mid-afternoon when most spores
are formed; this allows plants to dry before nightfall, reducing
the likelihood that sprinkling will promote other diseases.
Fungicides are only effective in early stages, not once there
is a lot of mildew. Fungicides should be specifically for
powdery mildew, and only used as a last resort for the highly
susceptible species listed above.
Chinese Elm Anthracnose
Most often seen on Chinese elm (Ulmus parvifolia), this
fungus causes branches to die back from the tips, promoting
a "frizzy hair" look to the tree. The ‘Drake’
variety of Chinese Elm is resistant to anthracnose, and is
the most common type of Chinese elm to be planted. In general
anthracnose is cosmetic and not fatal. To control, prune out
and dispose of infected twigs during the fall and winter.
Fungicides have not been found to be effective. For a photo
see this link: www.ipm.ucdavis.edu/PMG/S/D-WO-SULM-FO.003.html
Chinese elms that are not the ‘Drake’
variety may also get anthracnose canker, which looks like
large wounds in the bark. Consult an arborist for control
methods and consider replacing severely infected trees. For
a photo see this link: www.ipm.ucdavis.edu/PMG/S/D-WO-SULM-TR.002.html
For more info about anthracnose, see this link:
www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7420.html
Shot Hole Fungus
Affects Prunus species such as plum, almond and apricot.
In San Francisco, most often seen on purple leaf plums. Looks
like little holes in the leaves. Our warm wet winters and
wet springs encourage shot hole, but it is cosmetic and not
fatal.
Sooty Mold
Dark fungi that grow on plant surfaces that have been
covered with insect honeydew. Leaves will look black and "dirty."
See aphids and scale listings, above. Sooty mold in itself
is generally harmless and can be ignored, except when covers
leaves so much that they can’t get enough light. Fungicides
are not effective; instead, wash leaves with a forceful stream
of water and control the insects that are producing the honeydew,
usually for aphids. For a photo see this link:
www.ipm.ucdavis.edu/PMG/C/I-HO-CPSE-CD.002.html
Other Pest Resources
Free Sick Plant Clinic:
Berkeley Botanical Garden. On the first Saturday of each month,
9 to noon, UC plant pathologist Dr. Robert Raabe, UC entomologist
Dr. Nick Mills, and their team of experts, will diagnose what
ails your plants. (a picture or bagged sample may help) The
sick plant clinic is free with no reservations required. Directions
and info: http://botanicalgarden.berkeley.edu/program/index.shtml or call (510) 643-2755.
Strybing Arboretum sometimes has plant clinics.
For more information, call 415/661-1316 x354
Books:
Pests of Landscape Trees and Shrubs, publication # 3359 published by University
of California. Has very good pictures and a helpful tables
matching symptoms to causes. Available ANR Communication Services or call 1-800-994-8849. You also might find it at Strybing Arboretum Bookstore.
Write for advice:
In the Wednesday Chronicle: The Bug Man fagerlun@unm.edu
(note, he is from New Mexico, the bugs and solutions may be
different there)
Ask Dr. Hort home@sfchronicle.com
or send stamped self-addressed envelope to Dr. Hort, c/o SF
Chronicle, 901 Mission St, 94103
The Plant Doctor, Strybing Arboretum, education@strybing.org
or write to The Plant Doctor, c/o Leaflet, Strybing Arboretum
Society, 9th Avenue at Lincoln Way, San Francisco, CA 94122
Websites:
For more information about other pests and their least-toxic
control methods, visit these excellent sites:
San
Francisco Department of the Environment
UC
Davis IPM
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