NALP Cool Season Turfgrasses CH 8 (Managing turfgrass diseases) Exam Questions with Correct Answers
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Course
Environmental turf grass management
Institution
Environmental Turf Grass Management
Describe a disease cycle of leaf spot and melting out diseases: - Answer-The causal fungus survives the winter and crowns and roots of turf grass on turf debris on or in the soil. The fungus becomes active during the cool, wet weather of spring. Spores are produced by the causal fungus and leaves a...
NALP Cool Season Turfgrasses CH 8
(Managing turfgrass diseases) Exam
Questions with Correct Answers
Describe a disease cycle of leaf spot and melting out diseases: - Answer-The causal
fungus survives the winter and crowns and roots of turf grass on turf debris on or in the
soil. The fungus becomes active during the cool, wet weather of spring. Spores are
produced by the causal fungus and leaves and are released and splashed by rain to
newly emerging grass leaves, causing new leaf spots. Spores wash to the crown and
root areas, inciting the melting out phase of the disease usually by late spring or early
summer.
Describe the disease cycle a fairy ring: - Answer-They are produced by colonies of
mushroom fungi that live in soil and thatch. These colonies obtain food from decaying
organic matter and grow outward rapidly, increasing in size year after year. The ring of
stimulated grass is thought to be caused by nitrogen substances produced by the
breakdown of organic material by the fungi. The causal fungi are spread when fungal
threads, bits of mushrooms, or spores from the mushrooms are introduced into soil
under a turf area.
Describe the disease cycle for Dollarspot: - Answer-The fungus spreads via mycelium
on infected plant parts. Mycelium may be carried by the wind, water, or on turf
equipment and shoes. This fungus does not produce spores. Some species are thought
to survive during winter as sclerotia in dormant infected plant tissue.
Describe the disease cycle of brown patch: - Answer-The causal fungus over Winters as
tiny resting bodies called sclerotia, either within infected grass tissue or in the soil. The
fungus is capable of surviving in soil for years in the absence of a susceptible grass.
The fungus can cause disease when soil moisture's and humidity are high, night
temperatures are above 68°F and daytime temperatures average 80°F or above.
Describe the disease cycle of damping off disease: - Answer-When conditions are
favorable for grass seed germination and growth, early fall and spring, fungal organisms
that effect seedlings are usually of little significance. However, warm, wet weather is
more favorable for damping off fungi and less favorable for seedings. In warm weather,
higher than normal rates of seed may produce a very dense stand of seedlings that will
hinder the escape of moisture from the soil surface. Such wet conditions over long
periods of time are ideal for invasion by damping off fungi.
Describe the disease cycle of necrotic ring spot: - Answer-The fungus grows on the
surface of grassroots for most of the growing season without causing visible symptoms.
When conditions become favorable for the disease, the fungus attacks and destroys the
roots. It is unknown if spores are responsible for transporting the pathogen from one
, area to another. The disease is more severe during the cool periods of spring and fall in
some areas, while in others, the disease only occurs in mid summer. The disease is
generally more severe on drought stress turf, but can damage to roof growing in moist
soil's as well.
Describe the disease cycle of powdery mildew: - Answer-The causal fungus over
winters in dead grass and infected living grass plants. Spores of the fungus spread by
wind to leaves of other turf grass plants. Favorable conditions for the development of
this disease include poor air circulation, high atmospheric humidity, low light intensity or
shade, and cool air temperatures. Kentucky bluegrass, when planted in shaded areas,
is particularly susceptible to this disease.
Describe the disease cycle of pythium blight: - Answer-The fungi may survive for long
periods in the soil. Infected plant debris from the previous season or fungus spores in
the soil are sources of infection. Disease development from the first infection centers
occurs by growth of fungal mycelium and movement of spores from plant to plant.
Describe the disease cycle of rust diseases: - Answer-All but three of the dozens or so
species of fungi in this family go through five distinct spore production stages. Some of
these stages, which are necessary for the completion of the entire lifecycle, must occur
on plants that are unrelated to the grasses. This may include woody shrubs or grasses
and or herbaceous ornamental plants.
Describe the disease cycle of slime mold's: - Answer-They survive adverse conditions in
the spore stage. And cool, humid weather, the spores absorb water. The spores will
crack open, And a motile spore emerges. The motile spores feed on other micro
organisms and decaying organic matter, but do not infect living turf grasses. Eventually,
pairs of spores unite and increase in size. This form of the organism is called a
plasmodium, and it is this stage that produces the slimy overgrowth on turf grass is.
Slime mold plasmodia and reproductive structures may shade the grass leaves to the
extent that the leaves are yellowed, but damage seldom is severe
Describe the disease cycle of snow mold: - Answer-Sclerotia, the cause of gray snow
mold, oversummers in that thatch, clippings, and the crown area of the grass plants.
They germinate in fall and produce mycelial growth beneath the snow cover and infect
plants. In most instances, the fungus kills the blades of the plant, but does not kill the
crown and nodes.
Pink snow mold survives warm dry weather as dormant fungal mycelium or as dormant
spores in soil and thatch. Spores germinate and cool, wet conditions, producing
mycelium that infects grass leaves.
Describe the disease cycle of summer patch: - Answer-Because all fungus colonizers
grass roots in advance of disease causing activities. When conditions are favorable for
a disease activity, the fungus will invade the roots. Commonly occurs in mid summer
during extended periods of high temperatures following wet weather or heavy irrigation.
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