Blights, Scabs, and Spots are all types of fungal diseases
that attack plants. When the conditions
are right, fungi can bloom causing a stressful condition for vegetation. All types of plants are susceptible to fungal
disease, including: evergreens, broadleafs, and grasses. Advances have been made in resistant
cultivars of many species, resulting in a reduction of occurrences, but threats
keep coming as different strains of fungi are introduced.
Apple Scab
Notice the leaves of your ornamental crab apple or fruit
trees falling off in early summer? A
common cause is a fungal disease commonly known as Apple Scab. Spots on the leaves and fruit are a good sign
that there is a problem, usually insects or fungal disease, which would need to
be identified. Apple scab not only makes
a tree unsightly, it also stresses the tree, reduces tree vigor, and growth. Although Apple Scab itself does not kill a
tree, a severe infection over several years can lead to decline and eventual
death due to defoliation. Infected trees
look thinned out, undefined, and often littered from the leaf drops.
Often solutions are available, especially for ornamental
trees. The development of systemic
fungicides has allowed a technique that requires fewer applications and does
not require spraying a tree multiple times a season. Systemic fungicides move through the tree,
using the trees vascular system. They
are injected at the base of the tree. Once the disease is under control, treatment can be re-examined, and often
retreatments are not required annually to maintain, but every 2 to 3 years to
maintain control. This makes for a very
economical solution to a common problem.
Fruit bearing trees require treatments that will not
contaminate the fruit, so systemic fungicides are often out of the
question. There are topical treatments
that can be done to fruit bearing trees that will allow fruit to be
harvested. These usually require
multiple applications in a season, but if timed correctly can be successful.
Evergreens
Evergreens, namely Spruces and pines are extremely susceptible
to fungal disease. Needlecast is common
to spruces. While Pine Needle Tip Blight
commonly effects Pine trees. Both are
treatable but require different application methods and correct diagnosis.
Spruces take on the appearance of dying from the bottom up
when infected with Needlecast. When
observed closer many older needles will appear a dark shade of purplish black. Newly infected trees appear as if the tree is
thinning out and losing its needles, while trees with ongoing infections will
experience a dieback on the bottom branches due to defoliation. Another observation would be the large amount
of needles around the base of the tree that have fallen.
Pine Needle Tip Blight is very common, and is usually first
noticed as a thinning out of the tree. Upon closer inspection the actual blight can be seen on the needles,
which appears as a die back on the tip of the needles with very small black
spots. The best treatments are
preventative, but this is a curable disease.
Another evergreen that has recently been under attack are
boxwoods. Currently there is no curative
treatment, but it is being researched. Preventative action can help limit the spread of this disease but is
quite costly at this time. We are experimenting
with some systemic fungicides attempting control of this fatal infection. Stressed and newly planted boxwoods are
extremely susceptible, and the disease is often misdiagnosed as “winter damage”. There are several strains of boxwood that are
resistant to this disease and it is recommended to choose one of these
varieties.
Larger trees
Most have noticed black spots on Maple trees, this is called
tar-spot. It is a fungal disease that is
very common, and often treatment is unnecessary, as it typically does not pose
a major threat to the tree. There are occasions
when treatment is desired, for example: extreme defoliation, stress on tree, or
the disease causing an unsightly condition. Systemic fungicides have had a great record on controlling this disease.
Oaks have also been under attack by a fungal infection
called Oak Wilt. This is a very serious
disease, which will lead to the death of the tree. Prevention is key, once an infected tree
shows signs of decline it is often too late. Not all Oaks are as susceptible to Oak Wilt, so identification of the
species of tree is necessary to determine a treatment plan.
Grasses
Turf is home to a multitude of fungi. Often the growth of grass keeps up with any
damage that can be encountered. There
are times that favor development of these diseases and result in blooms which
can be noticeable. A common fungal
disease in turf is called Rust, due to the rusty color residue left by it. It is sometimes noticeable in the grass, but
is more often seen as stains on shoes after cutting a lawn and on turf care
equipment.
Another common fungi in nearly every lawn is Powdery
Mildew. This nearly never causes a
reason for concern, but is often noted when the disease is transferred to
garden and ornamental plants. It appears
as a white powder on leaves of plants, but nearly always goes unnoticed in a
lawn.
There are several others, these are just some examples to
give an idea of what else is going on in the lawn.
Summary
All diseases require 4 things to become an
issue. 1. Pathogen, 2. Susceptible host,
3. The correct environment, and 4. Time.
Control can be done in several ways using integrated pest management
techniques, and eliminating one or more of these items. When this is not an option fungicide control
is usually a viable option. If you need
help diagnosing, treating, or just concerns about the health of your plants;
contact us and we can see if treatment is an option.
