\m    20    4   98    2  1 'Ergot'
\m    45   13   99    2  1 'Dollar Spot'
\m    67   21    6    3  1 'Brown Patch'
\m    83   24  100    3  1 'Helminthosporium Leaf Spots'
\m   102   30   77    3  1 'Seedling Blight'
\m   117   33   63    4  1 'Root Rot'
\t'October 1987'                                                'IV F-'page
\a                  Dr. Tom Kucharek, Extension Plant Pathologist
\a
\a                       DISEASE CONTROL IN PASTURE GRASSES

                  Dr. Tom Kucharek, Extension Plant Pathologist




                       DISEASE CONTROL IN PASTURE GRASSES


\h 1 'Ergot'
                                     Ergot

CAUSE:  Fungus (Claviceps paspali).  Insects transmit this disease from one
seedhead to another.

SYMPTOMS:  Only the flower is infected.  The developing seed is replaced by a
white, sweet, sticky fluid (honey dew stage).  Infected flowers do not produce
viable seeds.  Infection is more likley to occur if wet weather persists
during flowering period.  In addition, wet conditions favor secondary fungi
colonizing honey dew stage.  This is exhibited by orange or black color to
infected flowers.  Ergot infected flowers not subsequently infected by
secondary fungi will produce the sclerotial stage.  This is the stage which is
toxic to animals.  The sclerotium is round and pale brown on the outside with
white and hard inner tissue.  It is 1/8 to 1/4 inch and nearly sphaerical in
shape.

HOST RANGE:  Argentine bahia, Paraguay bahia grass, and Dallis grass.

CONTROL:  Pensacola bahia grass is resistant.  Examine pastures if susceptible
grasses are used.  If seedheads are heavily infected, remove cattle from
pasture and cut off seedheads with a high set mower.



\h 1 'Dollar Spot'
                                  Dollar Spot

CAUSE:  Fungus (Sclerotinia homoeocarpa)

SYMPTOMS:  On fine textured grass, small patches about the size of a silver
dollar are killed.  On coarse textured grasses, such as bahiagrass, the grass
may be killed in a larger, more diffuse pattern.  This disease can be confused
with brown patch but characteristic leaf lesions of dollar spot are
characteristic of this disorder.  The lesions are on the leaf blades
especially at the margins.  They are light tan with a reddish-brown border and
usually radiate from the edge of the leaf.  Early in the day before the dew
dries, infected plants have a cobweb-like growth that can be seen.

HOST RANGE:  Bermudagrass, centipedegrass, ryegrass, bahiagrass, St. Augustine
grass, and zoysiagrass.

CONTROL:  In a pasture situation, an application of nitrogen fertilizer
retards the disease.
\b\v
\v
\v
\h 1 'Brown Patch'
                                  Brown patch

CAUSE:  Fungus (Rhizoctonia solani)

SYMPTOMS:  Grass is killed in roughly a circular pattern from a few inches to
several feet in diameter.  Often healthy grass grows back in center of
infected area giving a doughnut appearance.  Leaf sheaths are rotted.

HOST RANGE:  Extensive.

CONTROL:  Only control available for this disease in a pasture is to avoid
excess fertilization with nitrogen.



\h 1 'Helminthosporium Leaf Spots'
                          Helminthosporium Leaf Spots

CAUSE:  Fungi (Helminthosporium spp.)

SYMPTOMS:  Small (1/16-3/16") oblong purplish to brown spots on leaves.  Spots
may have a tan center.  Heavily infected leaves will wither and die.  There is
an over-all thinning of the turf.  May occur at any time of the year when the
grass is growing.  A rot of the leaf sheath may be evident.

HOST RANGE:  Many grasses including bermudagrass, zoysiagrass, St. Augustine
grass, rye grass.

CONTROL:  No practical control available for this disease on pasture grasses.
Earlier harvesting may be necessary.  Also controlled burns may reduce
future problems with this disease on bermuda grass.



\h 1 'Seedling Blight'
                                Seedling Blight

CAUSE:  Fungi (Pythium spp., Rhizoctonia sp.)

SYMPTOMS:  Seedling low in vigor and often killed before or just after
emergence.

HOST RANGE:  Extensive.

CONTROL:  Use high quality seed.  Treat seed with a fungicide (see section on
Seed Treatment).  Avoid planting deep.
\b\v
\v
\v
\h 1 'Root Rot'
                                    Root Rot

CAUSE:  Fungus (Pythium spp.)

SYMPTOMS:  Lower leaves become yellow.  Plants may appear to have nitrogen
deficiency.  Plants become stunted, brown and may die.  Patches of fields or
entire fields may be infected.

HOST RANGE:  Extensive.

CONTROL:  Bahiagrass is usually resistant.  Argentine bahiagrass has
been infected in turf situations.  Rejuvenating a pasture by burning and
disking has reduced Pythium root rot.  An application of nitrogen often allows
grass to outgrow effects of this disease.