STRIPE SMUT
- Pathogen:
Ustilago striiformis
- Grasses
Affected: Bent grasses
(Agrostis spp.), annual bluegrass (Poa annua), Kentucky
bluegrass (Poa pratensis), tall fescue (Festuca arundinacea),
sheep fescue (Festuca ovina), hard fescue (Festuca ovina var.
brachyphylla), perennial ryegrass (Lolium perenne).
- Season
of Occurrence: Major
symptoms are most evident during late winter and early spring.
- Symptoms
and Signs: Turf grass
plants colonized by the stripe smut fungus usually make slow vegetative
growth. Long, yellow green streaks
develop on the leaves of the affected plants, and as the disease progresses,
these streaks become gray. In the
final stages of disease development, the cuticle and epidermal cells
covering these streaks are ruptured, exposing the underlying, black spore
masses of the pathogen. After
this, the leaves split into ribbons and curl from the tips downward. The leaf blades then turn light brown,
wither, and die.
- Conditions Favoring
Disease Development: The
stripe smut pathogen is both seed and soil borne. The spores of the fungus begin growth
under soil conditions favorable for the development of turf grass seedlings. Infection of young
seedlings occurs through coleoptiles.
With older plants, tillers serve as the chief avenues of entry of
the pathogen. After penetration
has been accomplished, the fungus grows systemically throughout the host,
and it persists in the tissues throughout the life of the plant. The pronounced striping and shredding
of the leaves, however, is brought on by periods of cool air temperatures
and bright, sunny days. Plants
that have been growing at 90°F usually
do not show these symptoms. On the
other hand, when air temperatures are in the 50 to 60 degree range
striping and shredding of leaves can be very severe. Spring applications of high rates of
nitrogenous fertilizers can bring about a remission of stripe smut
symptoms; however, in the long run this practice actually causes an
increase in the intensity of the disease.
The incidence and severity of stripe smut will be lowest in turf
receiving adequate rates or balanced fertilizer, and highest in turf that
is growing under an imbalance of either nitrogen, phosphorous or
potassium.
- Control
(1) Cultural Practices: Some
of the damage caused by stripe smut can be offset by fertilization
practices that promote good growth of the affected turf. Applications of high rates of
nitrogenous fertilizers should be avoided. Instead the fertilizer should be a balanced formulation and
applied at intervals that provide a uniform rate of growth throughout the
season. Stripe smut diseased turf
is highly vulnerable to damage from heat and drought stress, therefore,
during hot dry weather it is important that particular attention be given
to addressing the increased irrigation needs of the affected area. (2) Call Empire Tree and Turf for a free estimate for a fungicidal
program for your turf grass.
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