Summer Patch
[Magnaporthe
poae]
SYMPTOMS
The
symptoms of summer patch appear in circular patches or rings, ranging from 6 inches
to 3 feet in diameter. Turf within these patches is initially off-colored,
prone to wilt, growing poorly, or sunken in the turf stand. Over a period of
one to two weeks, the turf continues to decline, turning yellow or straw brown
and eventually collapsing to the soil surface. The outer edges of the patch are
usually orange or bronze when the disease is actively developing. Affected
plants are easily pulled up from the turf, and visual examination reveals that
the roots, crowns, and rhizomes are black and rotten. The patches recur in the
same spot annually, and expand at a rate of 2 to 4 inches per year. Resistant
grasses, such as creeping bentgrass, fescues, or weedy species, are often
present in areas damaged by summer patch.
In temperate climates, creeping
bentgrass is resistant to summer patch and often remains completely healthy
when surrounding annual bluegrass is attacked. Creeping bentgrass can become
prone to the disease when grown in high-pH soils (>7.0) and subjected to
persistent heat stress. Several cases of summer patch have been documented on
bentgrass putting greens in the transition zone of the United States.
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summer patch crown rot on bentgrass
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Characteristic
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Description
|
|
Host
Grass Species
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creeping
bentgrass, annual bluegrass, Kentucky bluegrass, fine fescue
|
|
Month(s)
with symptoms
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June to
September
|
|
Stand
Symptoms
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spots,
circles, patches (4 inches to greater than 3 feet), rings
|
|
Foliar
Symptoms - Location/Shape
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dieback
from leaf tip, blighting of entire leaves
|
|
Foliar
Symptoms - Color
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tan,
yellow, orange
|
|
Root/Crown
Symptoms
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roots,
stolons, rhizomes, and/or crowns dark brown or black
|
|
Fungal
Signs
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none
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Note: Still not
sure if this is the right disease? The Turfgrass Disease
Identification program may be helpful. Or consult the experts at the Turf
Diagnostics Lab. Check the TurfFiles glossary for definitions
of unfamiliar terms.
FACTORS
AFFECTING DISEASE DEVELOPMENT
The summer
patch fungus begins to attack the roots, stolons, and rhizomes in the spring
when soil temperatures reach 65°F. Disease development continues as long as
soil temperatures remain between 65 and 80°F. Heat and drought stress during
summer induce the expression of summer patch symptoms. In North Carolina, the
symptoms typically appear in early to mid-July.
Summer patch is most severe when
soil pH is 6.5 or greater. In addition, any factor that restricts root growth
will also enhance the disease. Lush, succulent growth from excessive nitrogen,
potassium deficiencies, poor soil drainage, over-irrigation, excessive thatch
accumulation, and soil compaction have been shown to encourage disease
development.
CULTURAL
CONTROL
Maintain
soil pH between 6.0 and 6.5 to minimize summer patch development. Bluegrasses
are less tolerant of low soil pH than other turfgrasses, so use caution when
adjusting pH. Soil pH is best reduced slowly over time through use of an
acidifying nitrogen source, such as ammonium sulfate or sulfur-coated urea.
Avoid excessive nitrogen in the spring and fall, and mow at recommended heights
to maximize root growth.
Reduce thatch buildup and relieve
soil compaction through aggressive aerification, vertical mowing, and
topdressing. Frequent aerification is especially important in high traffic
areas where the disease is most severe. When summer patch symptoms appear,
increase mowing heights and the frequency of irrigation and fertilizer
applications to minimize stress and compensate for damage to the root system.
CHEMICAL
CONTROL
Fungicides are available for
summer patch control, but they are most effective when applied on a
preventative basis. For best results, fungicide applications should begin in
spring when soil temperatures reach 65°F. Two to three applications on 28-day
intervals provide excellent summer patch control in most situations. Fungicide
applications should be made in a high volume of water (5 gallons per 1,000
square feet) or watered in with 1/8” to 1/4" inch of irrigation
immediately after application.
|
Fungicide
|
Efficacy (1)
|
Resistance Risk (2)
|
Class (3)
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Products (4)
|
|
azoxystrobin
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++++
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3
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QoI
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Heritage
|
|
myclobutanil
|
+++
|
2
|
DMI
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Eagle
|
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propiconazole
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+++
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2
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DMI
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Banner MAXX, Propiconazole G-Pro, Propiconazole Pro,
Quali-Pro Propiconazole, Savvi, Spectator
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|
triadimefon
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+++
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2
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DMI
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Bayleton
|
|
trifloxystrobin
|
+++
|
3
|
QoI
|
Compass
|
|
thiophanate-methyl
|
++
|
3
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benzimidazole
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3336, Fungo, Systec, T-Storm
|
|
fenarimol**
|
++
|
2
|
DMI
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Rubigan
|
|
fludioxonil
|
++
|
1
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phenylpyrolle
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Medallion
|
|
pyraclostrobin
|
++
|
3
|
QoI
|
Insignia
|
|
triticonazole
|
?
|
2
|
DMI
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Trinity
|
|
fluoxastrobin
|
?
|
3
|
QoI
|
Disarm
|
|
** Not for application to
residential lawns.
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Footnotes:
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(1)
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Efficacy Codes:
|
|
|
++++
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excellent control when
conditions are highly favorable for disease development
|
|
|
+++
|
good control when disease
pressure is high, or excellent control when disease pressure is moderate
|
|
|
++
|
good control when disease
pressure is moderate, excellent control when disease pressure is low
|
|
|
+
|
good control when disease
pressure is low
|
|
|
0
|
does
not provide adequate control under any conditions
|
|
|
?
|
cannot be rated due to
insufficient data
|
|
(2)
|
Resistance Risk:
|
|
|
1
|
Rotating and tank-mixing not necessary,
but recommended to avoid potential side effects from continuous use of same
chemical class.
|
|
|
2
|
Rotate to different chemical
class after 3-4 applications; tank-mixing not necessary.
|
|
|
3
|
Rotate to different chemical class
after 2-3 applications; tank-mixing not necessary.
|
|
|
4
|
Rotate to different chemical
class after 1-2 applications; tank-mixing not necessary.
|
|
|
6
|
Rotate to different chemical
class after 1-2 applications; tank-mixing with low or moderate risk product
recommended.
|
|
|
9
|
Rotate to different chemical
class after EVERY application; tank-mix with low or moderate risk product for
EVERY application.
|
|
(3)
|
Continual use of fungicides
with similar control mechanisms (modes of action) can result in fungi that
are resistant to some chemicals. Poor or ineffective disease control can be
expected when this occurs. Managers can reduce the chances of this happening
by mixing or alternating fungicides belonging to different chemical classes.
|
|
(4)
|
Recommendations of specific
chemicals are based upon information on the manufacturer's label and
performance in a limited number of trials. Because environmental conditions
and methods of application may vary widely, performance of the chemical will
not always conform to the safety and pest control standards indicated by
experimental data. When more than one brand name exists for an agricultural
chemical, the name of brand that first came onto the market is listed first.
Otherwise, brand names are listed in alphabetical order. The order in which
brand names are given is not an indication of a recommendation or criticism.
|
|
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Recommendations for the use of agricultural
chemicals are included in this publication as a convenience to the reader.
The use of brand names and any mention or listing of commercial products or
services does not imply endorsement by North Carolina State University or
discrimination against similar products or services not mentioned. Other
brand names may be labeled for use on turfgrasses. Individuals who use
agricultural chemicals are responsible for ensuring that the intended use
complies with current regulations and conforms to the product label. Be sure
to obtain current information about usage regulations and examine a current
product label before applying any chemical. For assistance, contact your
county's Cooperative Extension agent.
|
© North Carolina State University. This information sheet was prepared
by Lane P. Tredway, Gail G. Wilkerson, Bridget R. Lassiter, Jenifer J.
Reynolds, and Gregory S. Buol. Departments of Plant Pathology and Crop Science,
College of Agriculture & Life Sciences, North Carolina State University.
Prepared April 29, 2008. Available on-line at
www.turffiles.ncsu.edu. This publication was made possible through a grant
provided by the Center for Turfgrass Environmental Research & Education
(CENTERE) whose purpose is to support worthwhile projects that will benefit
both the private sector and the public, and protect the environment.