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Questions?
E-Mail
Forestry Division
If
possible, take a couple of digital photos of your tree or shrub
and include them with your questions. One photo should be a close
up of the problem area. The second photo should be of the entire
tree if possible.
Sticky tree sap drips
on my car, what can I do?
If you park a vehicle under a tree and sticky spots get on your
windows and paint, the spots are usually not tree sap. Many types
of insects that feed on tree sap (sugars produced by the leaves
to supply food for the tree) excrete a sticky substance called
"honeydew." Sap-feeding insects such as, aphids
(which attack most types of trees), leafhoppers, treehoppers,
and soft-shelled scale
insects are the most common honeydew producers. By reducing or
eliminating the sap-feeding insects, the sticky "sap" problem
on vehicles and other things stored beneath infested trees is
reduced or eliminated.
If you see ants, bees or wasps frequently in your tree, you probably
have a sap-feeding insect problem. The bees, wasps, and most commonly
ants, are feeding on the honeydew produced by the sap-feeding
insects. Ants will protect the sap-feeding insects from their
natural insect enemies such as lady beetles and lacewings. Sticky
bands around the tree trunk traps ants crawling into the tree.
If ants can't get to the aphids, they can't protect them from
the flying lady beetles and lacewings.
Spraying the tree with an insecticide to get rid of the sap-feeding
insects can compound tree problems by killing beneficial insects.
The loss of beneficial insects allows spider mites, which are
unaffected by many insecticides (they are a type of spider and
not an insect), to explode in population size. Some pesticides
are labeled for both insects and spider mites. Follow the pesticide
label instructions and precautions precisely!
There are many types of control for sap-feeding insects and spider
mites. On smaller trees, shrubs, or other sturdy smaller plants,
insects and spider mites can be knocked off of the plant by a
strong stream of water. On smaller infested plants insecticidal
soaps or dish soaps such as Dawn® or Ivory®, diluted to
two tablespoons per gallon of water, can be sprayed on the soft-bodied
sap-feeding insects killing them. Insecticidal soaps can be obtained
in most garden centers. As with any pesticide, read the label
for precautionary statements when using on different plants. Soaps
used for insect pest control usually do less harm to beneficial
insects than the common insecticides. Some plants are sensitive
to dish soaps since the soap is not developed for use on plants.
Spray the leaves on an obscure limb. Wait a couple of days, if
nothing happens to the foliage, you are probably safe in using
it on the entire plant.
Some pesticides can be injected into the water conducting tissues
of the plant. These pesticides are restricted use and require
a state license to purchase and use. Some pesticides can be injected
with water into the soil around the root zone of the tree. The
tree will take in the pesticide with water into the root system.
The pesticide with the water will be systemically distributed
throughout the tree. Most insects feeding on the tree would be
killed. Systemic insecticides have the advantage of killing only
the insects that feed on the tree and not beneficial insects.
When soil or trunk injected pesticides are used, trying to find
an absolute calm day to spray the tree is not necessary.
Green Ash problems
Each year we are seeing green ash trees in Cheyenne
that had wilting or dying leaves on individual limbs or the entire
tree. Most likely this is related to the overall health of the
tree and the impact the drought is having on trees. It could be
insect related, see the article on ash
borer, or it could be a bacteria, fungus, or virus affecting
the trees.
Colorado
State Cooperative Extension has a good Website that talks
about the ash decline. They are dealing with the Colorado Front
Range which is 1000 to 1500 feet lower in elevation than Cheyenne.
Some trees they recommend for the Colorado Front Range may not
be suitable for Cheyenne.
What is Really Wrong with
my Tree
Most trees in the city are growing under constant stress. Their
roots have been paved or cemented over. The remaining soil has
been planted with nutrient and water robbing grass, and compacted
from frequent foot or vehicle traffic. Their trunks have been
scarred and bruised from lawn mowers, weed whips, and vehicles.
The soil around their roots has been polluted with runoff containing
herbicides, excess fertilizer, engine oil, gasoline, and other
chemicals from vehicles and industry. We try to hurry the process
of having a nice looking tree in our yard by buying the largest
tree possible, planting it in the smallest hole possible, pouring
on as much fertilizer as possible, to get it to grow as big as
possible, as fast as possible. This usually equates to weak wooded,
unhealthy trees with poorly developed root systems, that succumb
to insect and disease attack and struggle to live to one fourth
of their possible life span.
Most early tree death and health problems begin with any one
or a combination of the following: nutrient poor soils, plant
stock in poor condition, improper planting techniques, injury
to the bark or major limbs, incorrect pruning procedures, root
damage, too much herbicide applied in the root zone, over-watering,
under-watering, and/or severe cold or heat injury. Trees and shrubs
existing in a stressed condition caused by any one or more of
these problems are easy targets for insect and disease attack.
Insects and diseases are frequently the secondary problem
affecting a tree or shrub.
If a trench is dug in your yard to install a sprinkler system
and the trench is a foot deep and it is within five feet of a
tree trunk, there is a good chance that 40% of the feeder root
system of the tree has been severed. The tree will not usually
show an immediate decline when root, trunk, or branch damage is
done. The tree can store a large amount of water and food in its
limbs and trunk. When the food and water reserves are depleted,
the tree will begin to decline. The visible indication of decline
may begin weeks or years after the damage has been done. Decline
may begin with the tips of branches dying with leaves wilting
and fading in color or not leafing out in spring. The decline
continues with entire branches, progressively larger in size,
dying or not leafing out in spring, The decline may take months
or years before serious tree damage has occurred. But, premature
tree death or decline can frequently be traced back to significant
root loss or from any one or more of the causal agents listed
in the paragraph above.
Trees can withstand a fair amount of abuse, but no one knows
at what point the line between recovery and decline begins. Much
like humans, symptoms of poor health in trees and shrubs can be
treated, but until a lifestyle change is made, a healthy recovery
is elusive.
A
Comment on Insecticide Use - many insecticides will
also kill beneficial insects, which can lead to a spider mite
problem. Insecticides should be used as a last resort. Many common
insecticides are extremely toxic to birds, fish, pets, and humans
-- especially children. Frequent pesticide use actually promotes
the target insect pest to develop resistance. A few insects may
survive a specific insecticide treatment. These survivors then
go on to have progeny that have a higher chance of also resisting
future specific insecticide treatments. Safe and effective pesticide
use requires that the label is read and followed. Temperature,
wind, and precipitation, as well as the right pesticide application
for the problems are critical factors in successful and safe pesticide
application.
Decrease the
need for insecticides by planting trees and shrubs that are suitable
to our climate. Keep the trees and shrubs healthy with sufficient
water, and fertilizer as needed. Be careful not to underwater
or over-water the trees and shrubs. Avoid any kind of damage to
the trunk and root system. Use a mulch around the base of the
tree, in as large of an area as possible, to eliminate lawn grass
competition and the need to use mowers and string trimmers right
next to the bark.
A
Comment on Herbicide Use - Most herbicides are used
in lawns to kill broadleaf plants. Trees and shrubs are broadleaf
plants. Minimal herbicide use or best yet, no herbicide use near
trees and shrubs will help promote healthier trees and shrubs.
Lawn grass is more detrimental to tree and shrub growth than broadleaf
weeds. Some herbicides used in lawn care can stay in the soil
and build up in concentration during frequent and heavy applications
of weed killer chemicals, thereby slowly or quickly, depending
on tree health, causing damage to tree roots. Whatever calamity
befalls roots, so too will it affect the limbs and leaves. If
spray drift from herbicides used for lawn care gets on tree or
shrub leaves it will cause the leaves to die, deform, or discolor.
Browning
Foliage on Deciduous Trees (broadleaf trees)
Drought conditions can cause leaves to turn color and/or dry
up. Drought or lack of water causes the outer edge of the leaf
to brown progressing to the main leaf vein. Herbicides can cause
leaves to change color and/or turn brown. Frequently, herbicide
damaged leaves will distort in shape and then turn brown or fade
in color very rapidly. Various insects such as aphids, leaf hoppers,
and other sap feeding insects will cause leaf discoloration.
Spider
mites and microscopic eriophyid mites cause leaf discoloration.
Leaf fungal or bacterial diseases cause discoloration and browning,
click
here for further information on leaf diseases specific
to poplars and aspens.
Additional
information on insects can be found at:
University
of Wyoming - Cooperative Extension Service, publication
B-1035 is particularly helpful for tree care.
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