A Different
Year with Rain
Figure 1. The approach and front half of CDGA's
number two putting green at Sunshine Golf Course in Lemont,
IL on July 13, 2006. Notice all signs of summer stress are absent
on the L-93/G-2 creeping bentgrass blend as moderate summer
temperatures and adequate rainfall have prevailed. Figure 2.
(mouse rollover) Back half of the same putting green also displaying
excellent visual quality.
Weather Update
During the July 4th holiday weekend the high temperatures
of summer began. On July 6, 2006 isolated anthracnose basal
stem rot outbreaks affecting Poa annua in putting greens began
to appear in Illinois - related to midday wilt stress. And so
it went, transient weather conditions of hot weekends and mild
weekday temperatures occurred across the majority Illinois from
the end of June through the second week of July. This heat and
humidity pattern meant relatively moderate disease pressure
existed until Thursday July, 13.
Hot, humid weather had arrived, and was our first
real challenging week for turfgrass managers to deal with warm
temperature fungal pathogens, as well as decline of of cool-season
turfgrasses caused by supra-optimal temperature stress. Daytime
highs in the 90s F now settled in southern Illinois (Carbondale),
central Illinois (Bloomington and Peoria), as well as Chicago.
Rainfall on 11-12 July coincided with warm nighttime temperatures
and provided ideal conditions for our big three fungal turfgrass
pathogens of summer in Bloomington (1.5 inches) and areas of
Metro Chicago (2.5 inches in Lemont). These fungal pathogens
are; dollar spot (Sclerotinia homoeocarpa), brown patch
(Rhizoctonia solani), and Pythium blight (Pythium
aphanadermatum). Isolated Pythium blight outbreaks in fairways
were reported by superintendents in both Bloomington and Chicago,
whereas overly dry Peoria and Rockford were not affected by
this so-called water mold.
However, perhaps the greatest potential for fungal
diseases of turfgrass may have existed in southern Illinois,
where 2.75 inches of rain fell on Carbondale during 12 July
and was combined with a string of 90 F day / 70 F night temperatures.
However, the use of warm-season turfgrasses such as zoysiagrass
for fairways mitigates disease pressure in southern Illinois
compared to mid- and northern Illinois where cool-season turfgrasses
predominate.
Overall, the 2006 turfgrass growing conditions
thus far in Illinois have been excellent. As this month's newsletter
title suggests, summer rainfall totals have been more than adequate
at most Illinois locations compared to the extended drought
experienced the summer of 2005 (Table 1).
Table 1. Weekly rainfall totals from the end
of June to the third week of July for both 2005 and 2006 ( +
indicates increased precipitation in 2006 compared to same time
period in 2005).
|
Illinois
Location
|
Rain (in) -
June week 4
|
Rain (in) -
July week 1
|
Rain (in) -
July week 2
|
Rain (in) -
July week 3
|
|
2006
|
2005
|
Difference
|
2006
|
2005
|
Difference
|
2006
|
2005
|
Difference
|
2006
|
2005
|
Difference
|
|
Barrington
|
1.51
|
0.02
|
+ 1.49
|
0.65
|
1.18
|
- 0.53
|
0.06
|
0.01
|
+0.05
|
0.63
|
0.88
|
- 0.25
|
| Lemont |
1.48
|
0.00
|
+ 1.48
|
1.82
|
1.49
|
+ 0.33
|
2.45
|
0.91
|
+ 1.54
|
2.26
|
0.84
|
+ 1.42
|
|
Aurora
|
1.01
|
0.00
|
+ 1.01
|
0.55
|
0.44
|
+ 0.11
|
0.34
|
0.03
|
+ 0.31
|
0.19
|
0.50
|
- 0.31
|
|
Peoria
|
0.40
|
0.00
|
+ 0.40
|
0.08
|
0.33
|
- 0.25
|
0.10
|
0.44
|
- 0.34
|
0.72
|
0.21
|
+ 0.51
|
|
Bloomington
|
0.67
|
0.00
|
+ 0.67
|
2.26
|
0.50
|
+ 1.76
|
1.17
|
1.73
|
- 0.56
|
0.39
|
0.15
|
+ 0.24
|
|
Carbondale
|
0.35
|
0.00
|
+ 0.35
|
1.76
|
0.00
|
+ 1.76
|
3.22
|
2.66
|
+ 0.56
|
3.49
|
0.85
|
+ 2.64
|
Current Pests/Diseases
Our warm temperature fungal pathogens
have now been reported in all regions across Illinois. They
are the dollar spot (Sclerotinia homoeocarpa); brown patch (Rhizoctonia
solani); and Pythium blight (Pythium aphanadermatum). Additionally,
problems with anthracnose basal stem rot (Colletotrichum cereale)
and fairy ring (multiple basidiomycete fungi) continue to come
and go. Another generation of white grubs (moth and beetle insect
larvae) are again damaging turfgrass either by directly pruning
roots, or indirectly by encouraging bird feeding which scars
highly maintained golf course surfaces.
Dollar spot (Sclerotinia
homoeocarpa)
Dollar spot caused by fungus Sclerotinia homoeocarpa
first appeared in Chicago the first week of June. This was evident
at our research plots at North Shore Country Club where S.
homoeocarpa infection centers began to develop on the annual
bluegrass (Poa annua) component of the fairway, whereas
the creeping bentgrass remained disease free. On June 20, we
received the first report of significant dollar spot at a golf
course in far southern Illinois; Carbondale. This coincided
with our first outbreak of dollar spot in our creeping bentgrass
fairways here in Lemont, IL. For us, it was a good thing because
we could begin to generate some data on our fungicide test at
CDGA's Sunshine Golf Course. On Thursday June 23, myself, Lee
Miller, Randy Kane, and Carl Hopphan rated our dollar spot fungicide
trials for the first time at the CDGA's Sunshine Golf Course
in Lemont, IL . Disease levels were still low at that time (1
to 10% plot area blighted), but weather conditions continued
to favor infection center development by S. homoeocarpa
into July (Fig. 3).
Overall, this year's dollar spot observations
suggest that preventive fungicide programs to control the disease
should be timed according to turfgrass species. A predominately
Poa annua fairway would require earlier fungicide timing than
one of creeping bentgrass (could begin 2 weeks later in 2006).
This information seems intuitive, but is frequently not mentioned
by turfgrass plant pathologists.
Figure 3. Dollar spot fungicide research plots
on a creeping bentgrass/Poa annua fairway at North Shore
Country Club on July 5, 2006. The first significant wave of
dollar spot disease pressure here in Chicago occurred the end
of June. Compared to fairway edge, individual treatments can
be seen suppressing dollar spot (stringed rectangles).
The good news for turfgrass managers is that dollar
spot disease pressure has been moderate until the last week
of June in Illinois. This is simply because the preceding cool
environmental conditions were not favorable for its development.
S. homoeocarpa fungal growth is optimal when temperatures
are between 70-80 F and relative humidity is 85 percent or higher
(conditions that come together at night). Evening temperatures
during May and early June remained in the 50s to 60s F for the
most part.
Brown patch (Rhizoctonia
solani)
Brown patch is active when nighttime temperatures
are at 68 F minimum and 10 hours of continuous leaf wetness
duration exists. Late evening watering can get people into trouble
with brown patch because it jump starts the normal leaf wetness
period which is generally from 12 am to 8 am (8 hours). Night
temperatures in the 70s during July and August are ideal for
Rhizoctonia solani development. Typically, brown patch
does not completely kill the turfgrass, and instead causes blighting
in patches (Fig. 4) that thins the turfgrass within patches
by only blighting the lower leaf blades. R. solani does
not usually attack the plant crown, and so even when untreated
the turfgrass will recover even when a majority of leaves are
blighted (Fig. 5). On wide tall fescue blades, irregular lesions
can be found about mid-blade. The lesion interior is straw colored
with a dark chocolate red margin. This is in contrast to dollar
spot (Sclerotinia homoeocarpa) foliar lesions which are
a bleached white color and sometimes have a hour glass shape.
Figure 4. Brown patch disease visible on a
creeping bentgrass fairway as John Petrarca plays golf in Lemont,
IL on July 13, 2006. Figure 5. (mouse rollover) Continued 70
F nights and extended leaf wetness has allowed the patch to
increase up to 3 feet in diameter by 19 July (double the initial
size).
On July, 4 at CDGA's Sunshine golf course, I found
brown patch active on one of our L-93/G-2 creeping bentgrass
putting greens. It is also in a creeping bentgrass fairway which
we are using for dollar spot fungicide trials. I first noticed
what looked like brown patch activity on Friday June, 30. I
isolated Rhizoctonia solani over the weekend, confirming
my suspicion. We will withhold fungicides to the NTEP (National
Turfgrass Evaluation Program) plots and allow both brown patch
and dollar spot to damage the cultivars this month. A few creeping
bentgrass cultivars that have had excellent visual quality thus
far appear highly susceptible to brown patch. It is important
to note that I am no longer able to rate colonial bentgrass
(Agrostis capallaris) plots because they are now contaminated
with about 50% creeping bentgrass (Agrostis palustris).
Randy Kane felt the high genetic susceptibility of colonial
bentgrass to brown patch may have played a role in allowing
creeping bentgrass to encroach and out compete this otherwise
attractive, fine textured, dark green bentgrass. In Midwestern
and northern environs, R. solani typically only thins
the turfgrass in patches without killing the crown; the turfgrass
will recover without fungicide application. However, highly
susceptible turfgrasses such as colonial bentgrass, or any cool
season turfgrass grown in the deep south can be damaged beyond
recovery and require annual reseeding if fungicides are not
applied (something I witnessed last summer in the creeping bentgrass
plots of Dr. Lee Burpee in Griffin, Georgia).
Several options exist to control brown patch,
and even without control, lawns generally recover in 1-3 weeks
depending on the prevailing environmental conditions that influence
turfgrass growth. Brown patch can be controlled curatively (post-infection),
and chlorothalonil works well. However, because brown patch
blighting occurs very rapidly, curative applications will stop
disease progression but cannot always provide acceptable control.
Curative treatments are an option for fairways, roughs, and
sod, but not for putting greens.
For putting greens, preventive control is highly
recommended. Fungicides such as flutalonil (ProStar), or the
QoIs (Heritage, Insignia, and Compass) all provide excellent
control. The QoIs can provide 28 days control, whereas ProStar
provides 21 days. For my MS at Kansas State University, we found
azoxystrobin (Heritage) could provide near 100% control of brown
patch of tall fescue when applied every 35 days at 0.2 oz per
1000 sq ft preventively. This meant three applications of Heritage
could completely prevent brown patch all summer (1 June, 7 July,
14 August). However, the low rate did not suppress Pythium blight
(Pythium aphanadermatum); a common problem of tall fescue
(especially newly seeded) at midsummer during wet years. Instead,
Heritage seemed to exascerbate the fungal disease possibly because
those plots were dense, lush, and disease free (see Fig. 6 and
7 below).
Pythium blight
(Pythium aphanadermatum)
Pythium is classified in the family Pythiaceae
of the Oomycetes commonly known as water molds. In 1996, Pythium
was removed from the classification of true fungi, and was placed
along side brown algae in the kingdom chromista (Erwin and Ribeiro,
1996). One reason for this revision is that Pythium exists primarily
in its sexual fungal state during the majority of its life cycle,
whereas the fungi kingdom spends the majority of their life
cycle existing asexually (e.g. Rhizoctonia spp.). This
genetic difference is also reflected in the fact that a specific
chemistry is needed to suppress Pythium growth, whereas other
fungicide chemistries with a broad ability to suppress plant
pathogenic fungi usually cannot suppress Pythium growth. Therefore,
chemical control of Pythium is costly because it requires a
specialized molecule.
On 13 July, Pythium blight surfaced in central
Illinois when a golf course superintendent notified me that
he noticed initial signs of activity in low lying areas of his
L-93 creeping bentgrass fairways. The www.interactiveturf.com
Pythium blight model will begin to light up from now thru
August. Orange = daily ambient high temperature is greater than
86 F and the low is greater than 68 F. Red = the relative humidity
is greater than 90% for at least 9 hours. Any rain in the forecast
will easily tip the balance in the favor of the pathogen. The
P word always seems to bring Panic when thinking of putting
greens, but Pythium blight is primarily a problem of low areas
of fairways, roughs, and any turfgrass site with compaction
where soils poorly drain.
Figure 6. Kansas State University research associate Mark
Davis observes Pythium blight of tall fescue localized to plots
treated with azoxystrobin (Heritage) at Manhattan, KS during
July, 1999. Figure 7. (mouse rollover) Closeup shows cottony
mycelium and water-soaked foliar symptoms associated with Pythium
aphanadermatum infection.
Following the deluge of rain in central Illinois
on 12 July, Randy Kane also found Pythium blight the next day
in a Kentucky bluegrass rough at another golf course in central
Illinois. Pythium requires very wet conditions to be active
(standing water), and so soil at field capacity is dry for this
fungus - relatively speaking. We usually see Pythium appear
after a large rain down pour, or when an irrigation system malfunctions
and floods a site. Additionally, Pythium can appear when turfgrass
is overly dense and lush caused by high fertility or other cultural
factors (Fig. 6). Pythium blight has a unique symptom of coloring
the edge of the patch a distinct purple. Pythium produces a
lot of white mycelium (Fig. 7), but so does brown patch, and
dollar spot, so this characteristic will not guarantee you are
looking at Pythium blight. Pythium blight causes sunken, pitted
areas that appear greasy; the entire plant is killed from the
ground up. Foliar lesions are absent, unlike brown patch and
dollar spot. Instead P. aphanadermatum causes the entire
or portions of a leaf blade to become water-soaked. Pythium
produces motile spores called zoospores (flagella propel the
spores in water film), and is why streaking symptoms sometimes
occur across areas. Among the best Pythium fungicides are fosetyl
aluminum (e.g. Aliette Signature), metalaxyl (e.g. Subdue 2E,
Proturf Pythium Control), mefenoxam (e.g. Subdue MAXX, Quell),
propamocarb (Banol) and phosphite (e.g. Magellan, Biophos, Resyst,
Alude, and Vital).
Some interesting
things I've recently seen
Anthracnose basal stem rot (Colletotrichum
cereale) associated with fairy ring
 |
Currently, the majority of anthracnose
basal stem rot affecting putting greens in Chicago has
been associated with Poa annua suffering wilt stress.
Here, anthracnose basal stem rot selectively removes annual
bluegrass within localized dry spot areas that are occurring
within these fairy rings on the upper back edge of a putting
green. This disease outbreak followed the 4th of July,
the first really hot weekend in Chicago (7-6-06).
|
Sclerotinia homoeocarpa fungal mycelium and dew
 |
Conditions that favor fungal growth of
turfgrass pathogens are a combination of temperature and
extended leaf wetness. Foliar leaf wetness can be of two
possible sources: Dew, which is atmospheric moisture that
will condense as warm humid air cools during evening hours;
and guttation fluid, which is plant produced and exuded
through leaf pores called hydrothodes usually located
at the tips or edges of leafs. Here dew covers fungal
mycelium of Sclerotinia homoeocarpa infecting creeping
bentgrass (Agrostis palustris). S. homoeocarpa
is the causal agent of dollar spot disease (7-4-06).
|
Fairy ring puff ball
 |
A fairy ring puff ball rising to the surface
of a sand-based creeping bentgrass putting green (notice
sand particles still adhering to the fungal fruiting structure).
The term "fairy ring" dates to the Middle Ages
and is associated with myths and superstitions. The puff
ball or mushroom purpose is to release spores for fungal
dissemination by wind. It is thought that approximately
50+ basidomycete fungi cause fairy rings but this has
not been well studied. Oftentimes, fairy rings only darken
the turfgrass in an arc or circle. This is because the
fungi feed on organic matter in the soil/thatch, and then
release nutrients to the plant (7-5-06).
|
Little brown mushrooms follow
rain showers
 |
Referred to as LBD's by Lee Miller who
learned this from a university mycologist (a scientist
of fungi) in Georgia. Little brown mushrooms were evident
on a fairway at CDGA's Sunshine Golf Course following
a rain shower of 1.42 inches. The appearance of mushrooms
following rain is a common occurrence, and these are quite
probably Psilocybe semilanceata or Liberty Caps
(7-14-06).
|
Large
brown spores and hyphae of Glomus mycorrhizae
 |
A second case of
a mycorrhizal bloom is causing damage to a creeping bentgrass
putting green in central Illinois, and follows the initial
report of the disorder the second week of June here in
Chicago. This fungus has been identified as Glomus
sp. Both golf courses were affected with this rare and
unusual summer disorder of putting greens in 2005; originally
identified by Dr. Randy Kane. The overall symptoms look
like ball mark damage. To our knowledge, no one else in
the country is reporting a similar disorder of putting
greens (7-19-06).
|
Ascus and ascospores of Leptosphaerulina
fungus
 |
Many fungi inhabit the canopy of turfgrass.
Here, a sample of dormant Poa trivialis from a golf course
fairway is being investigated microscopically for the
presence of anthracnose (Colletotrichum cereale). Instead
the microscope reveals the fungus Leptosphaerulina
based on the identification of its spores. They are contained
in a sack-like structure called an ascus which always
yields 8 ascospores. This is a common saphrophyte of turfgrass
that is not pathogenic; Its presence only indicates the
normal decomposition of a senescent leaf blade (7-19-06).
|
Bird damage of a creeping
bentgrass putting green
 |
Birds feeding again on putting greens
are a good first indicator of new white grub generations
in the rootzone. Active moth larvae at this time are cutworm
(Agrostis ipsilon), and sod webworm (multiple genera
including the bluegrass webworm Parapediasia teterrella).
Beetles are also larval contibutors at midsummer. They
are the Japanese beetle (Popillia japonica); May
or June beetles (Phyllophaga spp.); northern and
southern masked chafers (Cyclocephala spp.); and
the black turfgrass Ataenius (Ataenius spretulus)
(7-20-06).
|
On-site research
Fairy ring study
update
Fairy ring is caused by a collection of basidiomycete
fungi that are capable of producing an aboveground fruiting
structure of either mushrooms (Agaricales) or puff balls (Lycoperdales)
(Fig. 8). Fairy ring has been assigned three types based on
symptoms, and if you have to deal with this issue you want a
higher number. Type 1 kill or badly damage turfgrass. Type 2
stimulates grass growth (dark green ring patterns) by releasing
nutrients following the degradation of organic material in the
soil/thatch layer. Type 3 exist as a ring of fruiting structures
in the turfgrass, but are otherwise benign. We are still dealing
with a Type 2 fairy ring at the Twin Orchard site in Long Grove,
Illinois, but eventually if damage progresses into localized
dry spot we may eventually see what is called a Type 1. This
is because the soilborne fungal mycelium creates hydrophobic
conditions in the rootzone; the effects of which are pronounced
during dry periods.
Figure 8. Close up of puff ball-like fruit
structures of a fairy ring fungus within the center of a faint
yellowish ring on a L-93/G-2 creeping bentgrass putting green
in Lemont, IL on July 19, 2006.
The Twin Orchard Country Club fairy ring study
on a Poa annua/creeping bentgrass putting green is yielding
some results. In this on-site study, we are evaluating the efficacy
of six fungicides to suppress fairy ring symptom development.
Nearly identical studies are being conducted at K-State by Drs.
Jack Fry (a former major professor of mine), and Mike Fidanza
at Penn State. Currently, the CDGA's study in Chicago is generating
the most data. This underscores why fairy ring is difficult
to work with, because year to year symptom development may not
always occur, or the rings change their location within a putting
green making data collection hit and miss from year to year.
Typically, when dry conditions are in the forecast, fairy ring
becomes more of an issue on golf course putting greens because
turfgrass can be killed by hydrophobic conditions (localized
dry spot symptoms) that occur at radial growth edge or within
the patch itself.
All fungicides chosen all have acropetal (systemic)
properties and are labeled for fairy ring control. They include
Bayleton, Prostar, Headway, Heritage TL, Banner MAXX, and Insignia.
ProStar is the standard for fairy ring suppression, but increasingly
golf course superintendents in the Midwest are using Bayleton.
Historically, most fungicides provide inconsistent and/or incomplete
suppression of fairy ring. This is because it is both difficult
to deliver fungicides into and below the thatch/hydrophobic
soil layer where the fungi are active, and approximately fifty
basidiomycete fungi can cause fairy ring. Therefore efficacy
may vary because the fungicide is absent or the fungicide does
not control the basidiomycete species you are facing. We predicted
we would see better control with fungicides when applied with
a wetting agent, but this is currently not the case; quite possibly
because we are experiencing a wet summer in Chicago. Currently
at Twin Orchard, we are seeing increasing fairy ring activity,
and preliminary information indicates both Bayleton (yellow
bar) and ProStar (dark blue bar) are providing the best control
compared to other fungicide treatments and the untreated control
(medium blue bar) (Fig. 9).
Figure 9. Bar graphs of percent fairy ring
development given application of six fungicides and one wetting
agent at Twin Orchard Country Club in Long Grove, IL. All fungicides
were applied at labeled rates every 30 days for fairy ring control
beginning 6 June, 2006 prior to initial symptom development.
Rating dates were 27 June (top) and 17 July (bottom).
+++++++++++++++++++++++
I hope this month's newsletter has been informative
and represents a partial running history of problems Illinois
turfgrass growers may have experienced thus far in 2006. Thank
you for your continued support of interactivetuf.com by providing
daily scouting reports and weather data submission via email.
Derek
Settle, PhD
CDGA
Turfgrass Programs
Midwest Golf House
11855 Archer Ave
Lemont, IL 60439
630-685-2307
