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From Gary's Tree Service: |
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Now that spring has almost arrived, take some time to learn about some of
the pests you are likely to find in your landscape this year. The following
is a fist of the most common pests we see regularly in the Lehigh Valley,
as well as tips on how to recognize them.
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Eastern Tent Caterpillar: This pest is most commonly found on
apples, flowering crabapples, and both wild and ornamental (flowering) cherry
trees. It is sometimes confused with gypsy moth caterpillars and Fail webworms.
The most distinguishing feature of tent caterpillars is that they form tents
in the forks of tree branches. They hatch in spring -about the time that
leaf buds open (Fall webworms occur later in summer and form nests at the
tips of branches).
Detecting tent caterpillars early and controlling them before they consume
much foliage is important to the vitality of the tree. However, you should
know that tent caterpillars rarely kill a tree.
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Hemlock Woolly Adelgid: This is a serious pest of the eastern
hemlock, our state tree. Look for white cottony masses on the undersides
and at the base of needles.
This pest gives an overall unhealthy look to the hemlocks it has infested.
The adelgids insert their piercing mouthparts into the base of the needles
or stem and suck out fluids. Left untreated, a tree can die within three
to five years.
Three applications of the control substances per year are recommended,
especially with severe infestations. We with a dormant oil application
in spring, followed by an application of insecticidal soap or horticultural
oil in late June or July and again in September to mid October.
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Lace Bugs: There are many species of lace bugs and generally each
feeds on one particular plant The most problematic ones in Pennsylvania are
found on azalea, cotoneaster, pieris, rhododendron, and serviceberry. They can
also be found on linden, Oak, pyracantha, and sycamore. One to three generations
of this insect can occur in a single growing season, depending on the species.
The insects pierce and suck fluid from leaf tissue, causing leaf discoloration,
reduced plant vigor, and premature leaf drop.
Lace bugs often go undetected at first because of their habit of staying
on the undersides of leaves. Early detection and control is best to prevent
population explosions and severe plant damage. Susceptible plants should be
monitored regularly. Start looking for flattened rectangular insects on the
undersides of leaves as the leaves unfurl in spring.
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Step 1: Fertilization
In response to the frequently asked question "Why should I fertilize my trees
when trees in the forest do just fine without it?" we have to examine the
different conditions under which these two groups of trees grow. There are
three basic differences to consider.
- Trees in the forest that survive do so mainly because of genetic
superiority-they are the fittest, On the other hand, trees in our landscapes
are relatively pampered both before and after they are permanently planted
to help them overcome any deficiencies.
- Second, nutrients needed by forest trees are replenished overtime
through the decaying process of materials shed from older trees such as
leaves, dead branches, etc. Trees in a more urban setting are usually
surrounded by lawns raked free of leaves and debris or by macadam or concrete.
- Third, trees in the forest have no need to produce balanced crowns or
regular shapes - they reach wherever they can for more light. But when it
comes to our yard trees, we expect them to conform to what we consider
appealing, and so we shape them, thin them, or shorten them as necessary.
All trees absorb oxygen, water, and nutrients through tiny hairs on
the fine tips of their roots. These feeder roots, as they are called,
often extend far beyond the circumference of the crown of the tree and
are usually located in the top few inches of the soil. Knowing this, it's
easy to see how root absorption of the trees in our landscapes is
restricted. Foot or vehicular traffic causes compaction, lawn grass
causes competition, hard surfaces divert or prevent contact with moisture
or nutrients and increase root temperatures to damaging levels.
The tree industry has developed ways to supplement the nutrient needs
of our trees through three fertilization methods. One is to drill holes
spaced around the trees' root zone and fill the holes with granular
fertilizer. Another method uses a highpressure gun to penetrate the
soil and dispense liquid fertilizer, A third method injects fertilizer
directly into the tree's "circulatory system" at the base of the trunk.
As far as timing goes, it is best to make the applications when root
activity peaks-either in the spring after the soil temperature moves
above freezing or in the fall after the first hard frost. Fertilizing
in the fall appeals to us as we have more time to do it then. Also
it provides the tree with some back-up nutrients to use immediately
after the leaves come out in spring - a process that requires a lot
of stored energy.
Step 2: Aeration
Tree decline can frequently be attributed to poor root growth and
function, and soil compaction often is the culprit. Research has
shown that by improving soil aeration, root growth and water uptake
can be enhanced. Thus the effects of compaction can be countered.
It is important first to understand what causes soil compaction.
Some factors such as foot and vehicular traffic are obvious, However,
there are other causes that are more subtle. For instance, the
force of vibration caused by traffic is transmitted to the surrounding
soil of nearby plantings. Another inadvertent means of creating
soil compaction is changing the grade or soil level around a tree.
Even several inches can be devastating - to say nothing of the
effect of changes of elevation in major construction! And, of
course, the type of soil itself may lend itself to compaction.
Fine- textured clay soils are much more prone to compaction than
coarse, sandy, or gravelly soils.
Soil compaction (and lack of aeration) inhibits root growth
and function in several ways. When the soil structure is altered
because of compaction, the size of soil particles and the pore
spaces between them are reduced and the flow of oxygen and water
is inhibited. Root growth may be restricted, and the ability to
absorb water and minerals is decreased.
So how can we counter compaction? There are several methods,
some of which are more suitable in particular circumstances.
- The most obvious is to eliminate the source of compaction
by controlling traffic or the extent of construction site. mulching
the root zone can also be effective as mulch doesn't compact readily.
These solutions may be impractical or impossible.
- Core aerating the turf can be of some benefit since many
tree roots are close to the surface, but this method will probably
be more beneficial to the turf. It doesn't hurt, however, and is a
great first step to addressing soil compaction.
- Amending the soil in the root zone to create a less compactible
structure is very effective. This frequently involves a large area
and may not be cost-effective.
- Vertical mulching is gaining popularity. It is a relatively
simple process and seems to be effective. Holes 2 inches wide are
drilled 10 inches to 18 inches deep at about 4-foot intervals in
the tree's feeder root zone. The holes are then filled with a
combination of a anticompaction agent and a granular root enhancer
or fertilizer.
- Another method similar to vertical mulching involves digging
trenches that radiate from the tree like spokes on a wheel and are
filled with amended soil material. This can be even more effective
than vertical mulching but must be done carefully so as not to
damage tree roots.
- Still another method uses a high-pressure soil probe to break
up the soil, This can be done with water or air pressure.
- Soil compaction or theneed for aeration due to a grade change
in the soil at a tree's root zone is a little more complicated to
deal with but may be necessary to save the tree. It involves
constructing a tree well to allow water and oxygen exchange to a
tree's root zone that has been buried under a certain amount of
soil.
A few winters ago, a large number of sycamore trees lining
the streets of Allentown's West End neighborhood developed extensive
frost cracks in the trunk area or large lower limbs. It is normally
thought that these cracks develop on the side of the tree that is
exposed to the early morning sun as a result of sunlight quickly warming
an area of bark and causing a crack in the wood from its expansion.
However, in this case, all of the cracks were on the side facing
the street, regardless of the direction of the sun. We finally determined
that the tree roots on the street side were under considerable stress
due to compaction and possible construction damage, and the resulting
loss of root function transferred this stress to that particular side
of the tree.
Step 3: Watering
Last, but certainly not least, we need to consider our trees need for water.
Inadequate watering, either too little, or too much is probably the most
frequent cause of tree decline. Insufficient rainfall is the culprit most
of the time. Four out of the last six years have been "drought years," as
far as our plants are concerned.
The main solution is irrigation, supplying water to supplement natural rainfall.
In general, this is necessary when establishing newly planted trees or whenever
there is not at least 1 inch of rainfall per week. (A downpour from a thunderstorm
cannot be counted accurately as the water runs off too quickly.)
Once you determine the need for irrigation, it is important to irrigate properly.
Sprinklers tend to throw water over large areas, which is fine for lawns but
usually ineffective and can be harmful for trees. Much of the water is lost
to evaporation (or to the lawn), and water that remains on leaves or bark too
long can promote fungus or other disease problems. Apply water directly to
the root zone by letting a hose drip slowly on it, by using a soaker hose,
or by using a root feeder that hooks up to a hose and dispenses water beneath
the soil. (These items are available at garden centers.) Water in the morning
whenever possible, and keep in mind that long, slow, and infrequent watering
is best.
What can make irrigation tricky is the type and quality of the soil. The
heavy clay soils typically found in this area can become impenetrable to water
as they dry out and turn rock hard. Bare soil dries out much more quickly
than soil that is mulched or has groundcover growing over it. Shady areas
and areas protected from wind also allow the soil to retain water longer.
All of these factors must be taken into account to ensure your trees get
the water they need.
The symptoms of water stress in trees may not be visible, at least not immediately.
Early leaf drop, wilting leaves, premature fall coloration, or leaves with dried
edges are often signs of water stress. However, most of the time trees react to
water stress internally, and signs may not show up for several years. By then the
damage may be irreversible. Water-stressed trees not only may experience dieback
but also may become susceptible to diseases.
With a basic grasp of the needs of your trees and an understanding of the mechanics
of their environment, you can take the proactive steps necessary to keep them healthy.
This is a lot easier and more satisfying than "playing catch up" later on.
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