Diseases ›

Leaf Spot

Symptoms

Leaf spot and melting out are common diseases in bluegrasses and bermudagrasses caused by species of Drechslera and Bipolaris (formerly known as Helminthosporium). In the bluegrasses, this disease is most active during warm and humid weather. In bermudagrasses, most damage occurs during cool and wet periods in the fall and spring, especially during periods of prolonged cloud cover. Leaf spot symptoms are expressed in the early stages of the disease, but if left uncontrolled, the pathogen may progress into the basal portions of the plant to cause ‘melting out’. Leaf spot symptoms initially appear as small, brown or black spots or flecks on the leaves or sheaths. As the lesions expand, the center of the lesions becomes tan with a dark brown or black border. The lesions may also be surrounded by a yellow halo. As the lesions expand, they coalesce and cause dieback of entire leaves or plants. Melting out symptoms appear as a reddish- brown rotting of the sheaths, crowns, rhizomes, or stolons which initially leads to wilting, yellowing, or death of the foliage. Symptoms of leaf spot and melting out appear in irregular patterns, although localized ‘hot spots’ may be more severely damaged than others.

Development Factors

Leaf spot/melting out is one of several Helminthosporium diseases which survive in thatch during periods that are unfavorable for disease development. These fungi are most active during periods of cool (60-65°F) and wet weather, but some are able to cause disease whenever temperatures are above freezing.

Leaf spot/melting out is most severe on turf that is growing slowly due to adverse weather conditions or improper management practices. Shaded areas with little or no air movement result in weak turf and extended periods of leaf wetness that favor disease development. Deficient or excessive nitrogen, excessive thatch, extended periods of leaf wetness, drought stress, and low mowing heights are factors that encourage the development of Helminthosporium diseases. These fungi may spread to the crowns and roots and cause melting out, which is most severe during periods of hot weather.

Certain cultivars of turfgrasses are very susceptible to injury from Helminthosporium diseases while many of the newly released cultivars have exhibited good resistance.

Cultural Control

Use turfgrass cultivars with resistance to this disease when available. Planting resistant cultivars is one of the most effective and economical ways to manage leaf spot and melting out. Refer to the results of cultivar evaluation trials operated by the National Turfgrass Evaluation Program or local Universities for cultivars with leaf spot resistance that perform well in your area. If planting cool-season turf, use blends and mixtures of multiple species and/or varieties when possible.

Fertilize to meet the nutritional needs of the turf but avoid over-stimulation and the development of lush, succulent growth. Do not apply more than one pound of nitrogen per 1,000 square feet in a single application. Mowing heights and frequencies should be within the recommended range for the turfgrass species being managed. Keep the mower blades sharp to prevent open wounds through which the fungus can enter.

Reduce extended periods of leaf wetness by watering deeply but infrequently to wet the entire root zone. Use the Turf Irrigation Management System available on TurfFiles to schedule irrigation based on weather conditions and turf needs. Do not irrigate just before sunset or after sunrise, because this will extend the leaf wetness period which favors disease development. Remove unwanted vegetation that impedes air movement and prune trees to allow for light penetration. Power rake or dethatch to remove excessive thatch and reduce the potential for pathogen survival. Regular aerification and topdressing of golf greens is also necessary to reduce thatch buildup.

Chemical Control

Leaf spot can be controlled on a preventative or curative basis. However, applications are most effective when made in the early stages of development. Once the disease reaches the melting out stage, fungicide may not cure infected plants but will help reduce further spread of the disease. Susceptible turfs should be monitored frequently for signs of disease activity during periods of cool and wet weather.

Fungicide and Formulation1
Amount of Formulation2
Application Interval3
Efficacy Rating
Resistance Risk
Fungicide and Formulation1

azoxystrobin
(Heritage, Strobe)
(Heritage TL)
(Heritage G)
(Strobe L)

Amount of Formulation2


0.2 to 0.4
1 to 2
2 to 4 lbs
0.38 to 0.77

Application Interval3


14 to 21
14 to 21
14 to 21
14 to 21

Efficacy Rating

++++



Resistance Risk

Medium



Fungicide and Formulation1

azoxystrobin + acibenzolar-S-methyl (Heritage Action)*

Amount of Formulation2

0.2 to 0.4

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

azoxystrobin + chlorothalonil (Renown)*

Amount of Formulation2

2.5 to 4.5

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

azoxystrobin + difenoconazole (Briskway)*

Amount of Formulation2

0.5 to 0.725

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

azoxystrobin + propiconazole (Headway)
ME
G

Amount of Formulation2


1.5 to 3
2 to 4 lbs

Application Interval3


14 to 21
14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

azoxystrobin + tebuconazole (Strobe T)*

Amount of Formulation2

0.75 to 1.5

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

chlorothalonil
(Daconil Ultrex)*

(Daconil Weather Stik, Legend)*

(Daconil Zn)*

(Chlorothalonil 500ZN)*

(Chlorothalonil 720SFT)*

(Chlorothalonil)*

Amount of Formulation2


1.8 to 3.25
3.7 to 5
2 to 3.6
4 to 5.5
3 to 5
6 to 8
3 to 5
7.9
2.12 to 3.5
5.5
1.8 to 3.2

Application Interval3


7 to 21
14 to 21
7 to 21
14
7 to 21
14
7 to 10
14
7 to 10
14
7 to 10

Efficacy Rating

++++










Resistance Risk

Low










Fungicide and Formulation1

chlorothalonil + acibenzolar-S-methyl (Daconil Action)*

Amount of Formulation2

2 to 3.5
4 to 5.4

Application Interval3

7 to 21
14

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + fluoxastrobin (Fame C)*

Amount of Formulation2

3 to 5.9

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

chlorothalonil + propiconazole (Concert)*

Amount of Formulation2

3 to 5.5
5.5 to 8.5

Application Interval3

7 to 14
14 to 21

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + propiconazole + fludioxonil (Instrata)*

Amount of Formulation2

2.75 to 6

Application Interval3

10 to 21

Efficacy Rating

+++

Resistance Risk

Low

Fungicide and Formulation1

chlorothalonil + thiophanate-methyl
(Spectro)*
(TM/C)*

Amount of Formulation2


3.72 to 5.76
2 to 8

Application Interval3


14
14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

fluazinam (Secure)*

Amount of Formulation2

0.5

Application Interval3

14

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

fluoxastrobin (Fame)

Amount of Formulation2

0.18 to 0.36

Application Interval3

14 to 21

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

fluoxastrobin + tebuconazole (Fame T)*

Amount of Formulation2

0.45 to 0.9

Application Interval3

21 to 28

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

iprodione (26GT, Iprodione Pro, IPro)*

Amount of Formulation2

3 to 4

Application Interval3

14 to 28

Efficacy Rating

+++

Resistance Risk

Medium

Fungicide and Formulation1

iprodione + thiophanate-methyl
(26/36)*

Amount of Formulation2


2 to 4

Application Interval3


14 to 21

Efficacy Rating

+++

Resistance Risk

Medium

Fungicide and Formulation1

iprodione + trifloxystrobin (Interface)*

Amount of Formulation2

3 to 5

Application Interval3

refer to label

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

mancozeb
(Fore)*
(Dithane)*

Amount of Formulation2


4
4

Application Interval3


7 to 14
10

Efficacy Rating

++++

Resistance Risk

Low

Fungicide and Formulation1

myclobutanil (Eagle, Myclobutanil)
penthiopyrad (Velista)

Amount of Formulation2

1.2
0.3 to 0.5

Application Interval3

14
14

Efficacy Rating

+

Resistance Risk

Medium

Fungicide and Formulation1

propiconazole
(Banner MAXX, Propiconazole)

Amount of Formulation2


1 to 2

Application Interval3


14

Efficacy Rating

++

Resistance Risk

Medium

Fungicide and Formulation1

pyraclostrobin (Insignia)
WG
SC

Amount of Formulation2


0.5 to 0.9
0.4 to 0.7

Application Interval3


14 to 28
14 to 28

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

pyraclostrobin + boscalid (Honor)*

Amount of Formulation2

0.55 to 1.1

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

pyraclostrobin + fluxapyroxad (Lexicon Intrinsic)

Amount of Formulation2

0.34 to 0.47

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

trifloxystrobin + triadimefon
(Armada)
(Tartan)*

Amount of Formulation2


0.6 to 1.2
1 to 2

Application Interval3


14 to 28
14 to 28

Efficacy Rating

++

Resistance Risk

Medium

Fungicide and Formulation1

triticonazole
(Trinity)
(Triton)

Amount of Formulation2


0.5 to 2
0.15 to 0.3

Application Interval3


14 to 28
14 to 28

Efficacy Rating

++

Resistance Risk

Medium

Fungicide and Formulation1

triticonazole + chlorothalonil (Reserve)*

Amount of Formulation2

3.2 to 4.5

Application Interval3

14 to 28

Efficacy Rating

++++

Resistance Risk

Medium

Fungicide and Formulation1

vinclozolin (Curalan, Touche)*

Amount of Formulation2

1

Application Interval3

14 to 28

Efficacy Rating

+++

Resistance Risk

Medium

1 Other trade names with the same active ingredients are labeled for use on turfgrasses and can be used according to label directions.
2 Apply fungicides in 2 to 5 gallons of water per 1,000 square feet according to label directions. Use lower rates for preventive and higher rates for curative applications.
3 Use shorter intervals when conditions are very favorable for disease.
* Products marked with an asterisk are not labeled for home lawn use.

Efficacy Rating
++++ = excellent control when conditions are highly favorable for disease development
+++ = good control when disease pressure is high, 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
? = not rated due to insufficient data

Resistance Risk
Low = Rotate to different chemical class after 3-4 applications; tank mixing not necessary
Medium = Rotate to different chemical class after 1-2 applications; tank-mixing with low or medium risk product recommended
High = Rotate to different chemical class after EVERY application; tank-mix with low or medium risk product for EVERY application
? = not rated due to insufficient data

Presentations

Publications

Species Data

Host species

bluegrasses, bermudagrass

field fungal signs sporetf ltc
field fungal signs sporetf ltc
field fungal signs sporetf ltc
field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf ltc
field greyleafspot leaflesionstf ltc
field greyleafspot leaflesionstf ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf ltc
grayleafspot leaf spotstf ltc
grayleafspot leaf spotstf ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
grayleafspot tf12 ltc
grayleafspot tf12 ltc
grayleafspot tf12 ltc
grayleafspot tf14 ltc
grayleafspot tf14 ltc
grayleafspot tf14 ltc
grayleafspot tf16 ltc
grayleafspot tf16 ltc
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grayleafspot tf19 ltc
grayleafspot tf19 ltc
grayleafspot tf19 ltc
grayleafspot tf20 ltc
grayleafspot tf20 ltc
grayleafspot tf20 ltc
grayleafspot tf22 ltc
grayleafspot tf22 ltc
grayleafspot tf22 ltc
grayleafspot tf2 ltc
grayleafspot tf2 ltc
grayleafspot tf2 ltc
grayleafspot tf5 ltc
grayleafspot tf5 ltc
grayleafspot tf5 ltc
grayleafspot tf7 ltc
grayleafspot tf7 ltc
grayleafspot tf7 ltc
grayleafspot tf8 ltc
grayleafspot tf8 ltc
grayleafspot tf8 ltc
grayleafspot tf ltc
grayleafspot tf ltc
grayleafspot tf ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsstaug ltc
greyleafspot leaflesionsstaug ltc
greyleafspot leaflesionsstaug ltc
field leafspot meltingoutbermuda ltc
field leafspot meltingoutbermuda ltc
field leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda ltc
red leaf spotbent5 ltc
red leaf spotbent5 ltc
red leaf spotbent5 ltc
red leaf spotbent6 ltc
red leaf spotbent6 ltc
red leaf spotbent6 ltc
red leaf spotbent ltc
red leaf spotbent ltc
red leaf spotbent ltc
Months with symptoms

March to June, Sept to November

Stand symptoms

irregular distribution across turf stand

grayleafspot4 ltc
grayleafspot4 ltc
grayleafspot4 ltc
grayleafspot tf12 ltc
grayleafspot tf12 ltc
grayleafspot tf12 ltc
grayleafspot tf14 ltc
grayleafspot tf14 ltc
grayleafspot tf14 ltc
grayleafspot tf16 ltc
grayleafspot tf16 ltc
grayleafspot tf16 ltc
grayleafspot tf19 ltc
grayleafspot tf19 ltc
grayleafspot tf19 ltc
grayleafspot tf20 ltc
grayleafspot tf20 ltc
grayleafspot tf20 ltc
grayleafspot tf22 ltc
grayleafspot tf22 ltc
grayleafspot tf22 ltc
grayleafspot tf2 ltc
grayleafspot tf2 ltc
grayleafspot tf2 ltc
grayleafspot tf5 ltc
grayleafspot tf5 ltc
grayleafspot tf5 ltc
grayleafspot tf7 ltc
grayleafspot tf7 ltc
grayleafspot tf7 ltc
grayleafspot tf8 ltc
grayleafspot tf8 ltc
grayleafspot tf8 ltc
grayleafspot tf ltc
grayleafspot tf ltc
grayleafspot tf ltc
field leafspot ltc
field leafspot ltc
field leafspot ltc
leafspot meltingout 4 ltc
leafspot meltingout 4 ltc
leafspot meltingout 4 ltc
leafspot meltingout 5 ltc
leafspot meltingout 5 ltc
leafspot meltingout 5 ltc
leafspot meltingout ltc
leafspot meltingout ltc
leafspot meltingout ltc
red leaf spotbent2 ltc
red leaf spotbent2 ltc
red leaf spotbent2 ltc
red leaf spotbent3 ltc
red leaf spotbent3 ltc
red leaf spotbent3 ltc
red leaf spotbent4 ltc
red leaf spotbent4 ltc
red leaf spotbent4 ltc
red leaf spotbent5 ltc
red leaf spotbent5 ltc
red leaf spotbent5 ltc
red leaf spotbent6 ltc
red leaf spotbent6 ltc
red leaf spotbent6 ltc
red leaf spotbent ltc
red leaf spotbent ltc
red leaf spotbent ltc
Foliar symptoms location/shape

oval leaf spots

field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf ltc
field greyleafspot leaflesionstf ltc
field greyleafspot leaflesionstf ltc
grayleafspot4 ltc
grayleafspot4 ltc
grayleafspot4 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf ltc
grayleafspot leaf spotstf ltc
grayleafspot leaf spotstf ltc
grayleafspot ltc
grayleafspot ltc
grayleafspot ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsstaug ltc
greyleafspot leaflesionsstaug ltc
greyleafspot leaflesionsstaug ltc
field leafspot meltingoutbermuda ltc
field leafspot meltingoutbermuda ltc
field leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda2 ltc
leafspot meltingoutbermuda2 ltc
leafspot meltingoutbermuda2 ltc
leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda ltc
field netblotchleaf spots ltc
field netblotchleaf spots ltc
field netblotchleaf spots ltc
netblotch leaf spots1 ltc
netblotch leaf spots1 ltc
netblotch leaf spots1 ltc
netblotch leaf spots ltc
netblotch leaf spots ltc
netblotch leaf spots ltc
redleafspot creepingbentgrass leafspot plantsymptom lbc
redleafspot creepingbentgrass leafspot plantsymptom lbc
redleafspot creepingbentgrass leafspot plantsymptom lbc
redleafspot creepingbentgrass plantsymptoms lbc
redleafspot creepingbentgrass plantsymptoms lbc
redleafspot creepingbentgrass plantsymptoms lbc
redleafspot creepingbentgrass plantsymptoms lesions lbc
redleafspot creepingbentgrass plantsymptoms lesions lbc
redleafspot creepingbentgrass plantsymptoms lesions lbc
Foliar symptoms color

yellow, tan, brown

field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions st aug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesions staug ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionsstaug2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf2 ltc
field greyleafspot leaflesionstf ltc
field greyleafspot leaflesionstf ltc
field greyleafspot leaflesionstf ltc
grayleafspot4 ltc
grayleafspot4 ltc
grayleafspot4 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf2 ltc
grayleafspot leaf spotstf ltc
grayleafspot leaf spotstf ltc
grayleafspot leaf spotstf ltc
grayleafspot ltc
grayleafspot ltc
grayleafspot ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
grayleafspot tallfescue plantsymptoms leafspots ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsst aug2 ltc
greyleafspot leaflesionsstaug ltc
greyleafspot leaflesionsstaug ltc
greyleafspot leaflesionsstaug ltc
field leafspot meltingoutbermuda ltc
field leafspot meltingoutbermuda ltc
field leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda2 ltc
leafspot meltingoutbermuda2 ltc
leafspot meltingoutbermuda2 ltc
leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda ltc
leafspot meltingoutbermuda ltc
field netblotchleaf spots ltc
field netblotchleaf spots ltc
field netblotchleaf spots ltc
netblotch leaf spots1 ltc
netblotch leaf spots1 ltc
netblotch leaf spots1 ltc
netblotch leaf spots ltc
netblotch leaf spots ltc
netblotch leaf spots ltc
redleafspot creepingbentgrass leafspot plantsymptom lbc
redleafspot creepingbentgrass leafspot plantsymptom lbc
redleafspot creepingbentgrass leafspot plantsymptom lbc
redleafspot creepingbentgrass plantsymptoms lbc
redleafspot creepingbentgrass plantsymptoms lbc
redleafspot creepingbentgrass plantsymptoms lbc
redleafspot creepingbentgrass plantsymptoms lesions lbc
redleafspot creepingbentgrass plantsymptoms lesions lbc
redleafspot creepingbentgrass plantsymptoms lesions lbc
red leaf spotbent ltc
red leaf spotbent ltc
red leaf spotbent ltc
Root/Crown symptoms

none

Fungal Signs

none

field fungal signs sporetf ltc
field fungal signs sporetf ltc
field fungal signs sporetf ltc