Needle Evergreen Diseases
Phomopsis sp. & Kabatina sp. are two
fungi that cause cankers on junipers (as well as other plants).
Phomopsis attacks only new growth and stops growing when
it gets too hot and/or dry. Kabatina attacks growth that
is two or more years of age. Both are fatal long term. Grow resistant
Cytospora sp. causes canker on spruces (as
well as other plants). The disease usually starts at the bottom
and works upwards most of the time. Occasionally kills from the
top down or from one side to the other. Sometimes Cytospora
kills piece meal.
There are several pine needle diseases. Brown spot
occurs in the spring as the new needles emerge. Death, browning
and defoliation usually occur by fall. In addition, the new twig
usually dies too. The disease often starts near the growth on the
north side and works up and around the tree as the disease progresses.
Needle cast occurs on current years mature
growth late in the growing season. Browning and defoliation of needles
usually occur the following growing season. The result over several
years is needles only on the current years growth. Needle
blight starts on any needle. Current year growth matures before
becoming susceptible. Needles often break off or fold at an angle
at the lesion. Most often associated with Christmas tree farms but
is becoming more and more a landscape disease.
Sphaeropsis sp. causes either tip blight
or canker problems on pine. Austrian pine is the most susceptible
pine. As a tip blight, the disease enters the candle as the new
growth emerges from the bud. Girdling eventually occurs and the
tip dies. A little later the dead tips dry out and turn brown. This
disease over winters on needles, dead tips, and pine cones. It does
not matter if the infected tissue is on the tree or on the ground.
Pine wilt is a disease caused by the pine wood nematode.
These nematodes can reproduce at an extremely high rate. The nematodes
eventually plug the plants vascular (xylem) system. The tree often
times dies in about two to three months. Keep plants healthy, avoid
injury or any long term stress to the pines. White pine is highly
resistant to this disease.
Sooty mold is a fungus disease. It grows on the
honeydew produced by "sucking" insects. Control the insects. Sooty
mold kills by cutting off light to the chlorophyll.
Die back is often the result of root rot. Root
rots occur due to poor drainage or over watering. There are several
root rot fungi. The root rot that tends to kill more tree roots
is one of the Phytophthora sp. Plant only in well-drained
soils and do not over water.
Natural needle drop (normal) is not a disease
even though many gardeners think it is. All evergreen needles eventually
die. The older needles are on the inside and usually die over an
entire growing season and, therefore, are not noticed. Occasionally,
they all die, turn yellow to brown together. This aging process
is normal and is not an infectious disease.
Mutations can change plants from one growth habit
to another such as a normal big plant to a dwarf. Sometimes these
mutations are not stable and may revert back to their original growth
Animals can cause noninfectious diseases. On evergreens,
deer and yellow- bellied sapsuckers are two of the more common animals
to cause injury. Sapsuckers punch holes in a straight line in the
trunks of many trees. Austrian and Scotch pines are the two evergreens
most often attacked. This bird is migratory through this area every
spring and fall. State, federal and international law protect it.
DO NOT harm this animal.
Excessive heat can cause severe injury to many plants
especially during drought stress or if the plant is not heat hardy.
There are other environmental conditions that cause noninfectious
diseases. They include drowning, cold injury, snow and ice.
Mites (MAY cause damage that looks like a disease
problem) are not insects but are considered insect related. Insects
have six legs. Mites have eight legs. The spruce mite is often the
mite that attacks the needle evergreens. It is a cool weather mite.
It feeds in the spring and fall when it is cool. During the heat
of summer the mite is not found but the damage becomes very noticeable.
A miticide is needed to control this pest. Insecticides may actually
increase the damage by killing the predatory mites and not the plant
April - May 2000: Gardening
with Hebs - Part 1 | Discouraging Canada
Geese | Needle Evergreen Diseases |
May Insect Problems