Localized
Dry Spot Prevalent During June
Figure 1. Distictive purple to red patches/strips
are symptoms of localized dry spot of a L93/G2 creeping bentgrass
putting green at Sunshine Golf Course in Lemont, IL on 5 June
2006.
Weather Update
Memorial weekend saw highs in the low 90s and
gave Illinois turfgrass managers a quick transition from spring
to summer. During the first week of June, dry conditions halted
the progression of dollar spot, and instead it was localized
dry spot sited as the most frequent problem encountered by golf
course superintendents. Here at CDGA's Sunshine Golf Course
in Lemont, IL localized dry spot (LDS) symptoms also plagued
our greens and tees. By the first week of June LDS had intensified
on elevated portions of our greens and was pronounced wherever
a wetting agent application had been withheld for comparative
purposes (Fig. 1). The putting green collar with its
greater mowing height and associated transpiration rate was
the first indicator of wilt and LDS. Dry conditions ended in
Chicago on 10 June when up to 2.5 inches of precipitation occurred
(see table below). Without that
rain event Chicago would be extremely dry and have only trace
amounts of precipitation. However, central and southern Illinois
continue to be very dry because the heavy rains of June 10th
were limited to northern Illinois. Localized dry spot of sand-based
putting greens continues to be a significant problem for golf
course superintendents in the central and southern and portions
of the state.
Current degree day (DD50)
and soil temperature values indicate Chicagoland and central
Illinois are cooler compared to 2005 (see
table below). In contrast, southern Illinois is warming
up faster this year and this directly impacts pest activity.
Currently, Carbondale is reporting that Japanese beetle numbers
are increasing. The dry, warm weather also causes fairy ring
symptoms to be pronounced, because fungal mycelium creates hydrophobic
conditions in the rootzone.
|
June 13, 2006
|
Base 50DD
Totals
|
Soil Temperature
|
Precipitation
June10 Event
|
Precipitation
Total
|
|
Location
|
2006
|
2005
|
Difference
|
2006
|
2005
|
Difference
|
inches
|
inches
|
|
N. Barrington
|
532
|
598
|
-66
|
64
|
67.1
|
-3.1
|
0.99
|
1.02
|
|
Lemont
|
619
|
692
|
-73
|
64.4
|
76.1
|
-11.7
|
2.38
|
2.43
|
|
Aurora
|
672
|
729
|
-57
|
68.2
|
73.6
|
-5.4
|
1.46
|
1.48
|
|
Peoria
|
915
|
998
|
-83
|
---
|
---
|
---
|
0.17
|
0.38
|
|
Bloomington
|
892
|
924
|
-32
|
69
|
---
|
---
|
0
|
0.04
|
|
Carbondale
|
1233
|
1090
|
+143
|
70.6
|
70.7
|
-0.1
|
0
|
0.02
|
Current Pests/Diseases
All the important beetle
species whose grubs are turfgrass pests have now been reported
in Illinois. 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).
Black turfgrass ataenius damaging
a fairway in Chicago
On 15 June, a Chicago suburb golf course fairway
was found to have high numbers of black turfgrass ataenius larvae
in the soil. The symptoms of the creeping bentgrass/Poa annua
fairway included wilt stress and a mottled necrotic color occurring
in patches and strips (Fig 2). The superintendent caught the
initial signs of damage by noting occurrence of wilt along the
fairway edges during this week when adequate soil moisture levels
existed. The symptoms of white grub root feeding can be confused
with localized dry spot, but is diagnosed when the sod can be
easily pulled up and away from the soil surface. If the sod
easily tears in long sheets like a carpet, it indicates the
roots that normally anchor the plant to the soil are gone; sheared
off by the chewing mouth parts of the black turfgrass ataenius
larvae. Additionally, at the soil-sod interface numerous small
grubs about ¼ inch can be found; frequently positioned
on their side in a crescent-shape (Fig 3). Interestingly no
bird or damage by small mammals had occurred, and unusual numbers
of adult beetles were not noticed the preceding month.
Figure 2. Symptoms of black turfgrass ataenius
grub root damage of a Poa annua/bentgrass fairway in a Chicago
suburb golf course on June 15, 2006. Figure 3. (mouse rollover)
The sod was easily pulled up, exposing multiple BTA grubs which
were feeding on the roots.
Black turfgrass ataenius were originally discovered
damaging turfgrass at a golf course in Minneapolis, MN in 1932.
Today, the black turfgrass ataenius is considered an important
pest of golf courses in nearly all the northern states. The
black adult beetle is very small measuring ¼ inch in
length. In spring, the beetles fly from hibernating sites which
is beneath the soil of wooded areas. The adult beetles begin
flight in May, and will lay eggs late May to early June; soon
thereafter the grubs begin feeding on turfgrass roots. The damaging
potential of Black turfgrass ataenius grubs should not be underestimated
because their numbers can reach up to 500 larva per square foot
beneath intensively managed turfgrass.
Soil moisture influences the egg laying of all
white grub beetle species. Adults are attracted to irrigated
turfgrass sites, and it is easy to see why golf course fairways
and greens are a magnet for white grub colonization. Eggs and
young grubs are vulnerable to desiccation, and so automatic
irrigation systems aid their survival and development in the
soil. A cultural practice that can reduce grub numbers is to
schedule deep, infrequent irrigation which allows intermittent
periods of low soil moisture to develop. In general, wet years
are associated with larger white grub populations, whereas numbers
during dry years are lower and less turfgrass damage is reported.
Here in Chicago, the cool wet weather conditions of May, 2006
were ideal for black turfgrass ataenius grub development.
Currently, preventive control of white grubs on
golf course fairways and putting greens is the norm. A few insecticides
with extended activity of up to two to three months are capable
of providing a window of white grub control during summer. The
recommended preventive grub insecticides include; imidacloprid
(Merit), and halofenozide (Mach 2), and isofenphos (Oftanol).
Most superintendents wait until 1 July, so the large and most
damaging second and third instar larval populations are suppressed
through September. Other insecticides (e.g. diazinon, carbaryl,
or trichlorfon) are used curatively to target existing grub
damage because they have good knockdown properties when ingested.
However, the curative materials have short residual periods
(3 weeks or less), and reapplication is often necessary. If
the product is not working after a few days, you probably need
to switch to another product. Timing is critical, and golf courses
with a history of black turfgrass ataenius activity will need
to schedule preventive applications earlier in the summer (June).
Arrival of root-rotting patch
diseases
Take-all patch (Gaeumannomyces
graminis var. avenae)
The first sign of take-all patch affecting a creeping
bentgrass fairway in a south Chicago suburb was reported on
June 8, 2006 by a superintendent. Take all patch is caused by
the soilborne fungus Gaeumannomyces graminis var. avenae
that attacks and rots roots. It is a serious disease of
newly established creeping bentgrass. Damage to roots is initiated
when dark hyphae (mycelium) penetrate into the vascular system.
This disrupts transpiration of water and nutrients, and leads
to wilt and plant death. Bentgrass resistance to take all patch
does not exist, but other turfgrass species such as Poa annua
are not susceptible. Initially bronze to bleached round patches
appear small, about cup-cutter size, but will continue to grow
in size up to several feet in diameter as years progress. Take-all
patch damage at the site was pronounced on the elevated edges
of the fairways existing as numerous, irregular, bronze-colored
patches (Fig 4 and 5). According to the superintendent's records
and our interactive turf database, this same fairway was affected
by take all last year at about the same time. This reflects
the fact that the root disease is a perennial problem associated
with the same location year after year, typically occurring
at the first sign of moisture stress.
Figure 4. Irregular distribution of Take-all
damage to a creeping bentgrass fairway in Chicago, IL on June
9, 2006. Figure 5. (mouse rollover) The superintendent uses
a soil probe to collect root samples which will be used to isolate
and identify the fungus.
Although patches are initially observed given
dry warm weather conditions exist (right now here in Chicago),
actual root infection actually occurred earlier this spring
when soil temperatures were cool (65 F or less). After three
to five years the severity of the disease decreases, and may
disappear altogether. The theory goes that antagonistic microbes
(fungi/bacteria) build up in the soil, and the site naturally
becomes suppressive to take all. However, it is important to
mention that this has not been the case on this golf course,
and the disease has been active on certain fairways for about
eight years without abatement. Warm soil temperature itself
will inhibit growth, and fits the superintendent's observation
that he sees recovery during summer.
Control options exist, but none will completely
control the disease. Dr. Peter Dernoeden showed acidification
of the soil pH by using ammonium sulfate or ammonium chloride
could reduce take all patch disease severity of creeping bentgrass.
Adequate levels of phosphorus and potassium are also recommended.
However, applying fertilizers with a high salt index increases
the risk of turfgrass injury. Also, calcareous soils with high
levels of limestone have a high buffering capacity and getting
the pH to budge using sulfur is very difficult if not impossible.
In 2003, Rutgers University researchers reported
manganese played an important role in the development of take-all.
They suppressed the disease with 2 lbs/Acre of Manganese (MnSO4)
when applied to a golf course fairway in either October or April.
The take-all pathogen binds up Mn surrounding the root, which
weakens the root and allows the fungus to infect and cause disease.
Optimal to high levels of Mn in the soil can reduce take-all
development, because the pathogen is less capable of starving
the roots of this essential element. This may explain why take-all
patch is most severe in greens with rootzones that have a pH
above 6.5, because a high pH ties Mn up in the soil and further
reduces its availability to roots.
Although the superintendent applied the QoI Heritage
(azoxystrobin) at its high labeled rate the end of April, no
apparent control was observed compared to an untreated portion.
This strategy follows the current chemical recommendations of
using acropetal (or systemic) fungicides such as DMIs (e.g.
propiconizole) and QoIs. Two applications are timed early in
the spring 30 days apart beginning when fairways are first clipped,
and then again about September when soil temperatures drop below
50 F. In the end, preventive control of take all patch on new
creeping bentgrass fairways is costly and never 100%. Instead,
perhaps the best option is the selection of cultural practices
that will promote healthy root development. Careful management
of irrigation to maintain adequate soil moisture is crucial
when roots are compromised by any pest.
Diseases/Pests
we've experienced thus far…
Rhizoctonia
zeae
Rhizoctonia fungi are some of the most important
soilborne pathogens of plants world-wide. They are everywhere
(cosmopolitan) probably because they are equally capable as
saprophytes of dead organic material, as they are as pathogens
of living plants. In Chicago, this has been a banner year for
Rhizoctonia zeae of Poa annua. R. zeae
can cause numerous bright yellow rings soon after a rain event
given cool temperatures (Fig 6). Individual rings can be relatively
small and measure only a few inches in diameter (Fig 7). Fortunately,
the effects of R. zeae are short-lived, and foliar discoloration
usually lasts about a week regardless of treatment. Warm summer
temperatures inhibit disease development of R. zeae, and so
this Rhizoctonia pathogen is limited to wet periods of the spring
and fall seasons.
If a Rhizoctonia-suppressive fungicide (e.g.
ProStar or QoIs) is applied preventively, you will not see this
disease. Firsthand, Lee and I saw this at a Chicago suburb golf
course where all the rings were limited to the green's approach
where no fungicide had been applied. In contrast, the rest of
the fairway which had received a fungicide application was clean
and without disease. Even so, the bright yellow rings that selectively
attack Poa annua are temporary and last about a week and then
disappear as the discolored leaf blades are clipped off.
Figure 6. Yellow ring symptoms in patches of
Poa annua caused by Rhizoctonia zeae whereas the bentgrass
component of the fairway is disease-free. Figure 7. (mouse rollover)
Lee Miller samples a R. zeae ring in Chicago, IL on May
31, 2006.
Some interesting
things we've recently seen
Red Thread (Laetisaria fuciformis)
mycelium
 |
Red thread affecting a Kentucky bluegrass
rough surround of a putting green. The fungal pathogen
is Laetisaria fuciformis. White to pinkish cottony
flocks of mycelium can be present on leaves. These were
1-2 mm in diameter with spiky edges. The leaves were necrotic
from the tip down affecting the turf in circular patches
1 foot or less in diameter. Within
the patches the blighting was diffuse, and so the damage
was not overly obvious. (5-31-06)
|
Lightning strikes a putting green flag pole
 |
The effect of a lightning striking to
a putting green soon after the storm had passed. The blasted
flag remaining on the green was burnt and torn and had
to be replaced, whereas the green recovered in about a
week with few ill effects (5-30-06).
Photo credit: Todd Schmitz
|
Cotton fluff in a fairway
 |
Sometimes mistaken as fungal mycelium,
cotton fluff is the product of the female cottonwood tree
(Populus deltoides) who's seeds are tufted to allow
dispersal by wind. Here, the fluff had formed into balls
which were moving down the slope of a fairway (5-10-06).
|
Glomus mycorrhizal disease of
bentgrass
 |
This very odd condition has only been
seen on new (renovated in the last 3-4 years), "gassed
and regrassed" greens. Visually, the condition is
like a mini-localized dry spot. In two years this is our
third confirmed diagnosis of this condition, the first
being in Bloomington, IL and two now in Chicago. Glomus,
the fungus believed to be responsible, is normally a beneficial
mycorrhizae. The spots are about the size of a ball mark,
initially red to copper then become necrotic. The thatch
layer beneath is very hard and can be felt with an index
finger. The assoicated soil/thatch smells distinctly like
fish --more--
(6-12-06).
|
On-site research
Fairy ring study
Figure 8. Lee Miller waters in a wetting agent
applied with a fungicide to evaluate preventive control fairy
ring on a Poa/bentgrass putting green at Twin Orchard Golf Country
Club in Long Grove, IL on June 6, 2006. Figure 9. (mouse rollover)
Battery-powered thermocouple sensors are installed to measure
soil temperature throughout summer.
At Twin Orchard Country Club we have begun a fairy
ring study on a Poa annua/creeping bentgrass putting
green to evaluate the efficacy of six fungicides to suppress
symptom development. In July 2005, this practice putting green
had an abundance of fairy ring that was well distributed throughout.
The fungicides are applied with and without a wetting agent
to suppress fairy ring symptom development (Fig 8). We will
also monitor the ability of a wetting agent to influence soil
temperature (Fig 9). Fairy ring is caused by numerous soilborne
fungi of either mushroom (Agaricales) or puff ball (Lycoperdales)
types. Nearly identical studies are also being conducted at
K-State by Jack Fry, and Penn State by Mike Fidanza.
All fungicides chosen have acropetal (systemic)
properties, and include Bayleton, Prostar, Headway, Heritage
TL, Banner MAXX, and Insignia. Historically, fungicides have
provided inconsistent suppression of fairy ring, and is thought
due to the difficulty of delivering them into and below the
thatch/hydrophobic soil layer where the soilborne fairy ring
fungi are active. Therefore, in conjunction with fungicide application,
any cultural practice like coring, spiking, and watering-in
is recommended. In our study, we are predicting that we will
see better control with fungicides when applied with a wetting
agent. This is based on 2005 information from Drs. Fry and Fidanza
in which good fairy ring symptom suppression occurred with a
wetting agent alone, or with fungicides plus a wetting agent
compared to fungicides alone in their creeping bentgrass putting
green studies.
Lee Miller will be leaving the CDGA at the end
of this month to pursue his PhD degree at North Carolina State
University with Dr. Lane Tredway. The turfgrass pathology program
at NC State is one of the finest in the country. Over a period
of approximately four years, Lee will intensively study fairy
ring of highly maintained turfgrass. Fairy ring continues to
be very difficult to control, in part because it has not been
adequately studied. Without a doubt, turfgrass managers and
the field of turfgrass pathology will benefit from the fairy
ring investigations that Lee is about to begin in North Carolina.
+++++++++++++++++++++++
Thanks for your support of this, as well as all
of our turfgrass research programs.
Lee
Miller
CDGA
Manager of Turfgrass Research
Midwest Golf House
11855 Archer Ave
Lemont, IL 60439
630-685-2305
Derek
Settle
CDGA
Manager of IPM Programs
Midwest Golf House
11855 Archer Ave
Lemont, IL 60439
630-257-2307
