disease cycle of fungus Rhizoctonia solani which cause Brown patch in turf grass and the control methods

1. Brown
patch

2.  Brief introduction
 Factors leading to epidemic
 Symptoms
 Disease cycle
 Economic importance
 Control measures

3.  Brown patch is a disease of turf grass caused by
soil borne fungi Rhizoctonia solani
 they are present in practically all soils throughout
the world and compose of a large number of
strains or races that attach to a wide range of
different plants including vegetables, flowers and
field crop
 The disease is also known as Rhizoctonia blight or
sheath blight
 Another species of fungus Rhizoctonia zeae is
more potent agent of brown patch that primarily
attack perrenial ryegrass and creeping bentgrass
on golf courses

4. nutritional category
 The fungus itself is a necrotrophs as it release
toxins which kills the cell before it feeds on it
leading to appearance of lesions in infected
leaves
 The fungus has a wide host range as it affects
turf grasses, flowers, vegetables and field crops

5.  Brown patch usually develops on lawns during
periods of wet overcast weather in late spring
or fall
 Damage is heavy after several days of showers
with day temperatures of 15-26 degree Celsius
 Excessive nitrogen and thatch often leads to
outbreak of brown patch
 High nitrogen promote growth of succulent
leaves that are susceptible to Rhizoctonia solani

6.  Brown patch first appears in lawns as small
circular areas several inches in diameter which
quickly increase to 3-6 feet
 Leaves first become water soaked, then wilt
and finally turn brown
 On broadleaved turf grass like St Augustine
turf grass distinct tan coloured leaf spots
surrounded by soaked margins are sometimes
seen

8.  On tall fescue, symptoms of brown patch can
be observed on individual leaves and not
necessarily in patches.
 Symptoms on leaves appear as irregular tan or
light brown lesions surrounded by dark brown
borders.
 In severe cases, the entire stand may look
discolored and thinned

10.  Symptoms also appear as watersoaked and
dark purplish green colour “smoke ring”
 This soon dries, wither and turn light brown
with dead leaves remaining upright
 Algae often invade diseased patches and may
cause hard dark crusts
 When attack is severe crown rhizomes, stolons,
roots turn brown and rot often killing large
areas

12.  Source of inoculum
 Rhizoctonia solani fungus survive from year to
year principally in form of rounded brown
resting bodies called bulbis
 The bulbis are found in thatch, diseased grass
tissue and top half inch of the soil
 Bulbis are extremely resistant to heat, cold,
drought and fungicides

13.  Germination
 When conditions are favourable ie temperature
of 8-15 degrees celcius the bulbis germinate
 Each bulbis germinate by sending out delicate
threads or hyphae in a radial pattern through
the upper soil and thatch
 Penetration
 The hyphae penetrates and infect grass plants
through leaf spores(stomata), directly through
leaf and stem or via mowing wounds

14.  The fungus grows throughout the leaf tissue
growing up over the grass leaves and sheaths
 The spread from one leaf to another occurs
through droplets of dew or guttation water
exuded at the leaf tip
 Nutrients and organic compounds like amino
acid in guttation water stimulates fungus
growth
 As long as the temperature is favorable, the
mycelium within grass clippings or thatch
resumes growth and initiates new infection

15.  Overwintering
 When conditions becomes unfavourable for
like air temperature reaching 35 degrees
Celsius the fungus sporulates
 It forms a bulbis which may stay in soil for
many years in dormant state waiting for
availability of host and favourable
environmental conditions

16.  Brown patch reduce quality and standard of
golf courses leading to loss of income to club
owners
 Soccer stadium may not be recommended in
hosting international events like world cup
hence loss in foreign currency of a nation

17.  Cultural method
 Removal of dew or guttation water that collects
on the grass leaves each morning is an effective
aid in reducing brown patch
 This can be achieved by dragging a water horse
across the area
 Irrigation of the grass must be done during
midday leaving time for the grass to dry before
nightfall

18.  Fungicides like Chipco 26GT is required on
high value bentgrass turfs
 It is usually made on curative basis, the first
spray should be applied immediately after
onset of symptoms especially if prolonged hot
humid weather is expected
 In areas were brown patch cause severe
thinning on putting greens, preventative
fungicide application may be justified

19. Clemson cooperate extension. 2013. Home and
Garden information centre:pdf available @
( http://www.clemson.edu/extension/hgic)
Krouse ,J.2011. Brown Patch:pdf. University of
Maryland , Symons hall. New Jersey
Landschout , P. 2010. Managing turf grass
disease:pdf. Pennsylvania State University,
available @ (agsci.psu.edu)