 Anthracnose
of Trees and Shrubs
Necrotic spots or scorch-like blight on leaves. During, or shortly
after wet weather from late spring until late summer, irregular lesions
emerge and kill areas of the leaf. On sugar maple lesions are reddish
brown. Very young leaves attacked may become blackened and shriveled,
but infected mature leaves retain normal form. |
 Arborvitae
Leaf Minor - Damage starts in tips of shoots causing leaves
to be yellow or brown. Hold up to light to look for larvae within
the leaf. If not too severe, prune off brown foliage.
Spruce
Spider Mites - Damage occurs to oldest (interior) leaves
appearing as yellowing or stippling of foliage. Tap branches over
a white piece of paper, mites will appear as dust-like specks moving
about. White fast moving mites are predacious, feeding on the pest
mites. If these are seen, do not spray. They will control the pest.
|
Apple
Scab
Appears
as olive brown spots on the leaves and fruit in summer.
Reduce overwinter source by removing leaves and apples
from last year. Good pruning will reduce number of sprays needed.
Apply a registered fungicide from tight cluster (flowers buds visible
but no color) until 2 -3 weeks after petal fall. Do not apply captan
within 10 days of a dormant oil spray. |
Bacterial
Blight of Lilac
Causes new growth to turn dark brown and die back quickly. Cut out
and destroy infected shoots as soon as symptoms appear disinfecting
tools between cuts. When severe, spray with copper fungicides once
in mid-September. |
Birch
leaf Minor
Causes dark greenish spots expanding to blotches on leaves
of birch. Mostly cosmetic injury only. Control first generation is
most important. Highly visible specimens can be treated with acephate,
dimethoate, and Imidacloprid (soil drench in November or March). |
|  Bark
splitting
Bark splitting can be caused by wounds from pruning, insect borers,
mechanical damage from mowers and line trimmers, canker diseases
or planting too deep. The only thing that you can do to help is
to perform basic tree care; mulch around the trunk, water when the
soil is dry under the mulch (check weekly during dry periods), and
do not fertilize after June, if at all. If the tree is small, it
may grow around the wound.
|
 Black
Knot on Cherry
Hard black growth on branches of cherry or plum trees. The black knot
fungus gall (the hard black growth) takes two years to develop. In
the first year it just looks like a swelling or split in the branch.
If you do not cut these out, more galls will develop. You can still
cut them out this year. Try to get to them before the leaf and flower
buds open. You can also apply a protective fungicide spray in spring
when the flowers are opening. Check the pesticide label for directions. |
 Bronze
Birch Borer
The larvae is a grub that tunnels under the bark disrupting the flow
of water up the tree. This is likely the cause of the wilting branches.
Sapsuckers and wood peckers dig into the bark to get at the grubs.
Keeping European birch well watered and fertilized can sustain trees,
however, this tree looks to be in poor condition and may be too far
gone. Take care of the other trees by mulching around the base, and
watering during periods of drought. |
 Carpenter
Ants and Wood Decay
Carpenter Ants do not cause decay or tree cavities. They
just take advantage of dead wood. Decay softened the branch wood
within the trunk of the tree pictured at right after a large limb
was removed. Carpenter ants excavated the decayed wood. The ribbing
on the interior is the result of the ant’s preference for
the softer spring wood growth and leaving the denser summer growth
of the annual rings. No treatment is necessary.
|
  Cedar
Apple Rust
On Junipers and red cedars, prune out the red-brown, round or spindle
shaped swellings (picture at right) of cedar apple rust and quince
apple rust just before swellings begin. The orange jelly-like masses
release spores that infect the alternate host (apple, hawthorn) in
the second phase of this disease. |
| |
 Diplodia
Tip Blight
Infection begins on buds, succulent stems, elongating shoots
and sometimes on immature needles of pine in spring when shoots begin
to grow. Drops of resin exude from small lesions on twigs near tip
of branch. Lesions enlarge and shoots stop growing before or during
needle elongation. Dying shoots turn yellow-green to straw color causing
characteristic tip blight. Lesions become resin soaked and dark reddish
brown in summer. In autumn, presence of black fruiting bodies may
be found on needles and cones. |
 Dogwood
Anthracnose
Shortly after leaves have expand (mid-late May and June),
spots and blotches appear on infected leaves. These spots have a tan
center and a purple or reddish margin. On the bottom of the leaf,
tiny brown or black spots may appear beneath these lesions. Blotches
can also occur at the tip or along the margin of the leaves –
these too have a tan center and purplish margin. |
 Dutch
Elm Disease
First seen in the US in the '30's. It still kills elm trees. Early
symptoms consist of yellow and flagging of leaves. Isolated trees
may live for many years before becoming infected with the disease.
Trees infected with the disease can not be cured. The only control
is preventing the disease from becoming established. The elm bark
beetle spreads the disease so control should be targeted at them.
Dead elm trees should be cut down and all bark removed to kill over
wintering beetles if the wood is to be stored for firewood. |
 Eastern
tent caterpillar (pdf)
Feed
on leaves of many fruit trees during the night and hide in tents
during the day. Trees are not harmed unless defoliation approaches
100%. However, if trees have been stressed previously, defoliation
should not be allowed to exceed 50%. If defoliation is high (especially
with young trees) use a registered insecticide. Or, tents can be
be pulled out with a stick and destroyed. Do not burn out or prune
indiscriminately.
|
European
Chafer
At dusk you may notice thousands of beetles flying around trees. The
bugs are light brown/gold in color and are about 1/2 inch long by
1/4 inch wide.The beetle does not harm trees but the grub,
which will be hatching from eggs in August (the adults are mating
now), can cause damage to the roots of grass. You can check for the
grubs in late August or early September by peeling back a layer of
sod. If you see 8-10 grubs per square foot, then you may want to treat
the lawn with an insecticide for grubs. Contact your local Cooperative
Extension or nursery for recommended chemicals. |
 Fireblight
Leaves die back quickly and blackening affecting trees and shrubs
in the rose family (rosacea), particularly ornamental apples, pears
and MT Ash. Carefully remove and dispose of infected branches as soon
as they appear. Cut at least 6-12" below signs of infection.
Prune out any remaining cankered branches during dormant season. Avoid
high rates of nitrogen. |
 Gypsy
Moth Caterpillar
Gypsy moth caterpillars can cause early defoliation of many trees.
If the tees are healthy and haven't been stressed the previous year,
no control is necessary. Look for caterpillars that looked shriveled,
and hang down in an inverted "V" (picture right). This indicates
that parasites are killing the caterpillars. |
 Honeylocust
Plant Bug
Damage
to Honeylocust trees in spring can be recognized by stippling, deformity
and defoliation. Nothing can be done once damage is seen, but plan
to spray with horticultural oil next spring from late April through
early May. |
Honeylocust
Pod Gall Midge
New leaflets appear red and swollen from pod gall midge.
Severe infestations may require insecticide treatments. Horticultural
oil is the only general use spray. |
Japanese
Beetles
Feeding on leaves does not substantially hurt the tree. You can try
Japanese beetle traps to lure the beetles away from your plum. Using
the traps actually increases the number of beetles in an area, so
place them 100 yards or more away from the plants your protecting.
Controlling grubs
in the lawn may help if you have a large lawn. But check for grubs
in late August by pealing back sod and counting grubs. 5-8 grubs/sq
ft indicate a high population however they may not be Japanese beetle
grubs so you may need to have them identified at your local Cooperative
Extension. |
 Leaf
Blister of Oak
Leaves
become infected just as buds open. Bulges are seen on the leaf surface,
or depressions as viewed from the reverse side. Numerous blisters
sometimes coalesce and involve the entire leaf. |
Leaf
galls
Pods on leaves of various sizes and shapes that exist
on many different trees species and do not harm the tree. The gall
on the leaf of ash is called the Ash midrib gall and is caused by
a small fly-like insect called a midge. |
 Lichen
A blue-green fungus that grows on bark of trees. Lichen are non-aggressive
to plants and colonize after the plant is under stress in humid shaded
locations. The slow growth of stressed plants give lichen a foothold
to start growing. Lichen are formed by a symbiotic relationship between
a fungus and an algae. The algae produces sugar through photosynthesis
which feeds the fungus and the fungus collects moisture and nutrients
for the algae. Removing lichen from a plant causes more harm than
leaving it. |
 Magnolia
Scale
The insect appears as a brown "bump" on the twig. The young black
crawlers of Magnolia scale will be present in early October signaling
the next opportunity to control this insect. Apply horticultural oil,
insecticidal soap, acephate, carbaryl, or Malathion, as crawlers appear.
Imidacloprid (soil drench), or dormant oil could be used in early
spring (April). |
 Maple
Decline
Maple
trees under some kind of stress (soil compaction, drought, flood)
may loose leaves or branches. Leading causes, that I see, is soil
compaction/poor drainage and trunk injury. Soil compaction is heavy,
hard soil that does not allow water and air to filter through and
may impede root penetration. Compaction may occur naturally in clayey
soils or be created by vehicles or even foot traffic. Early fall
color, or discolored leaves may be due to other unidentified
stress problems.
|
  Maple
Trumpet Skeletonizer
The leaves of maple curl and turning brown. Open up the rolled
leaves to find the "trumpet" that this leaf feeding caterpillar
hides in. Late season leaf loss causes no harm to trees so control
is unnecessary. |
 Oak
Anthracnose
Trees in the "white oak" family are susceptible to oak caused
by the fungus Apiognomonia sp. Newly expanding leaves develop brown
spots and shrivel up. Severe cases can cause branch dieback but t
is too late for control now anyway (June). The best thing that you
could do would be to remove the fallen leaves in autumn to reduce
the spread of the disease to next years leaves. In severe cases fungicides
before bud break will prevent a second occurrence. |
|
  Pear
thrips
Maple
leaves damaged by the pear thrips are dwarfed, mottled yellow to green-brown,
and distorted. This causes the tree to have a thin crown, and the
effect resembles late frost damage. Blister-like scars develop along
the veins and petioles of the foliage. Moderately damaged foliage
can place the trees under some stress and possibly cause premature
leaf drop in early fall. |
 Pine
Gall Rust
Globose
or pear shaped woody galls form on branches of pine trees, on main
stem in some species. Galls enlarge to 1-10 cm before dying. In May
and early June powdery yellow-orange spores appear. In second year
and third year galls develop bark collars at one or both ends.
|
 Powdery
Mildew
A white powdery fungus that appears on leaves. It will
not effect the long term health of the shrubs. To reduce the occurrence
in the future, be sure the shrubs are in full sun and get good air
circulation - thinning pruning of over head trees and thinning the
shrubs themselves can accomplish this. |
 Quince
Rust
Fruits of hawthorn or crabapple become uniformly
covered with tiny horn-like projections and then die and dry out.
|
 Rhabdocline
needlecast
Appears
as purplish-brown bands, or spots, on the needles of douglas fir.
First look for discolored needles near the base of the tree. Apply
a registered fungicide when 50% of the buds have opened. Severely
infected trees should be cut and removed. |
 Sapsucker
Injury
Sap
suckers create a series of hole like this - 00000. They eat the insects
that are attracted to the sap and will reopen the holes as the sap
stops flowing. This damage can eventually kill areas of the trunk
or girdle the tree. |
 Sooty
Mold
A black fungus that forms on the secretions (honeydew) of
aphids and scale insects. |
Spruce
Gall
Cooley spruce gall adelgid causes small, pineapple
shaped galls on the ends of branches. Treat mid-to-late April, before
galls appear, with horticultural oil (do not use on blue spruce). |
 Tar
Spot
Affects Norway maple (including Crimson King that is mistakenly
called "red" maple) causing large black spots on leaves
and may cause early defoliation. In severe cases, the leaf also shows
a wilting or scorching. This disease of the foliage does not harm
the tree so control is not warranted. Remove leaves or mulch them
to reduce occurrence of the disease next year.
|
 Viburnum
Leaf Beetle
The grubs riddle leaves of Snowball bush and other viburnums with
holes, in some cases causing them to shrivel up. In July, the adult
beetle emerge and may cause further defoliation of susceptible species.
|
White
Pine Weevil
Causes the top of white pine or spruce to turn brown and wilt over
like a shepherds crook. Prune out and destroy the brown, crooked leaders
before late July before the larvae emerge as an adult beetle. Other
pines and firs may also be attacked. |
  Winter
Injury
Damage to plants from roadside salt can become evident by various
symptoms. Evergreens (spruce, pine) will show brown or yellow needles
(see winter damage below). On deciduous plants (trees an shrubs that
loose their leaves in winter) salt spray causes buds to die and new
sprouts to form right below them resulting in a witches broom effect. |
