Copper Spot
[Gloeocercospora
sorghi]
SYMPTOMS
Copper
spot is a disease of bentgrass species that develops during periods of warm and
humid weather. Velvet bentgrass is particularly susceptible to the disease, but
it is occasionally observed on creeping bentgrass as well. As the name implies,
copper spot appears in small spots, usually less than 3 inches in diameter,
that are copper or salmon in color. The disease causes a foliar blight, so
distinct lesions or leaf spots are not evident on individual plants. When the
turf is wet or humidity is high, the infected leaves may be covered with a
thin, gelatinous coating of fungal spores.
Copper spot can often be confused
with dollar spot, which produces very similar symptoms. These diseases can be
easily distinguished early in the morning when dew is present on the turf. The
dollar spot fungus produces white, cottony masses of mycelium on the infected
turf, whereas copper spot produces gelatinous masses of spores that are copper
or salmon in color. In addition, the outer margin of a copper spot is typically
more diffuse than a dollar spot, which has very well defined edges.
|
copper spot
|
Characteristic
|
Description
|
|
Host
Grass Species
|
creeping
bentgrass, annual bluegrass
|
|
Month(s)
with symptoms
|
April
to September
|
|
Stand
Symptoms
|
spots
|
|
Foliar
Symptoms - Location/Shape
|
blighting
of entire leaves
|
|
Foliar
Symptoms - Color
|
tan,
orange, red, pink
|
|
Root/Crown
Symptoms
|
none
|
|
Fungal
Signs
|
mycelium,
jelly-like spore-masses
|
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
Copper spot develops during
periods of warm, wet weather. The pathogen is most active when temperatures are
between 65°F and 85°F. High humidity, frequent rainfall, or over-irrigation
favors rapid infection and heavy sporulation. Unlike dollar spot, the
development of copper spot is enhanced by excessive nitrogen levels. The
disease is also more severe when soil pH is 5.5 or lower.
CULTURAL
CONTROL
Avoid excessive nitrogen by using
granular fertilizers with a blend of quick and slow release forms. In general,
no more than 0.25 lb of water-soluble nitrogen should be applied to creeping
bentgrass at any one time. Removal of dew in the morning by mowing, whipping,
or dragging will shorten leaf wetness periods and discourage copper spot
development. Practice deep and infrequent irrigation to minimize periods of
leaf wetness. Prune or remove trees surrounding golf course putting greens to
increase air movement and sunlight penetration. Installation of high-powered
fans will also help to minimize copper spot development in areas where air
movement is restricted. Creeping bentgrass performs best when soil pH is
between 5.5 and 6.5, but pH should be maintained above 6.0 where annual
bluegrass is being cultured. Annual soil testing should be used to determine if
lime applications are needed to maintain soil pH in this optimal range.
CHEMICAL
CONTROL
Little is known about the
performance of fungicides for copper spot control. Where the disease has been a
persistent problem, apply a labeled fungicide every 14 to 21 days when
conditions are conducive to copper spot outbreaks. In other areas, the disease can
be controlled curatively if it is detected early. Tank-mixtures of contact and
systemic fungicides are most effective after copper spot symptoms appear.
|
Fungicide
|
Efficacy (1)
|
Resistance Risk (2)
|
Class (3)
|
Products (4)
|
|
thiophanate-methyl
|
+++
|
6
|
benzimidazole
|
3336, Fungo, Systec, T-Storm
|
|
flutolanil + thiophanate-methyl
|
+++
|
6
|
carboxamide + benzimidazole
|
SysStar
|
|
iprodione + thiophanate-methyl**
|
+++
|
6
|
dicarboxamide + benzimidazole
|
26/36
|
|
triadimefon
|
+++
|
4
|
DMI
|
Bayleton
|
|
chlorothalonil + thiophanate-methyl**
|
+++
|
4
|
nitrile + benzimidazole
|
ConSyst, Spectro
|
|
mancozeb**
|
++
|
2
|
dithiocarbamate
|
Fore, Dithane, Protect
|
|
mancozeb + copper hydroxide**
|
++
|
2
|
dithiocarbamate
|
Junction
|
|
chlorothalonil**
|
++
|
2
|
nitrile
|
Daconil, Chlorostar, Echo, Manicure
|
|
chlorothalonil + fenarimol**
|
++
|
3
|
nitrile + DMI
|
TwoSome
|
|
maneb**
|
?
|
2
|
dithiocarbamate
|
Pentathlon
|
|
thiram**
|
?
|
2
|
dithiocarbamate
|
Spotrete
|
|
fenarimol**
|
?
|
4
|
DMI
|
Rubigan
|
|
myclobutanil
|
?
|
4
|
DMI
|
Eagle
|
|
** Not for application to
residential lawns.
|
|
Footnotes:
|
|
(1)
|
Efficacy Codes:
|
|
++++
|
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.
|
|
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 Fred Yelverton, Gail
G. Wilkerson, Leon Warren, Travis Gannon, and Gregory S. Buol. Department of
Crop Science, College of Agriculture & Life Sciences, North Carolina State
University. Prepared November, 3, 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.