$ Spot Lingers,
Anthracnose Cranks Up
Weather:
The temperatures have remained
quite mild in northern Illinois, considering this is supposed
to be the hottest month of the year. Although we are only a
degree below the normal average at O'Hare, we have had the fewest
number of days above 85 degrees (11) here in the last 59 years.
These cooler days have kept many warm weather pests in check,
but those that prefer a milder temperature regime have flourished.
Rainfall throughout the region is running just about on average
in northern Illinois too, with halfway through the month msot
areas at about 50-60% of the normal total.
As you drift down the state though,
the story changes considerably. Bloomington, Peoria, and Urbana
have been cool, but a little wetter, and locally VERY wetter
in areas that were hit by that slobberknocker of a storm cell
last Tuesday that spurned some dangerous tornadoes and those
mammatus clouds around Chicagoland - click
here if you missed them. Springfield has been
very wet, with rainfall totals through the first half of the
month already above the normal totals for the month. Carbondale
has been dry and super hot - running about 3 degrees above normal
for the month and at only 30% of the normal rainfall. And if
you think it was hot here on Sunday and Monday try Carbondale's
heat indexes of 110-115!
The huge differences in weather
make it impossible to paint with a broad brush on turf health
and pest problems for the entire state. Forecasts call for a
mild and very nice weekend for the area, and turn a little hotter
mid next week as the jet stream is expected to lift and allow
hot air and humidity up from the South. The past two times this
year they called for a warm spell I sounded the bell for warm
weather diseases to occur and very little happened. I'll try
and learn my lesson and stay mum for now...
Diseases:
The last newsletter had the shortest disease section,
and this may be one of the longer ones. Basal rot anthracnose
on Poa (and one foliar case on Penncross) has hit courses near
Rockford and Bloomington this past week, at sites where preventive
fungicide schedules specifically targeted for the disease had
been implemented. Frankly, this leaves us and the superintendents
who are having the outbreaks scratching our collective heads
as to what went wrong. One major factor leading to anthracnose
outbreaks is a lack of nitrogen available to the plant, so if
you are having problems adding a shot of soluble N to the
tank may help. Anthracnose loves a stressed or wounded
plant as well, so practices like topdressing and low mowing
can exacerbate symptoms considerably. The bright spot in some
of these outbreaks is that most bentgrass cultivars except Penncross
and Pennlinks are pretty tolerant of this disease, so you might
be able to interseed and/or get some other bentgrass to encroach
in. In fact, now is the most effective time to try and interseed
bentgrass into Poa - click
here to see more info on overseeding in OSU's turfnotes.
This will be of little solace to those who have large Poa populations
on greens that may check out and cause scarred and unputtable
surfaces.
Another factor to the anthracnose outbreaks could
be fungicide resistance, as many areas such as Kentucky and
Georgia have already found anthracnose resistant to the QoI
fungicides (Heritage, Compass, Insignia) develop and cause problems.
The pathogen, Colletotrichum graminicola, is a very heavy
spore producer and, like Pythium, snow molds, and others that
share the trait, is therefore a likely candidate for resistance
problems. Like the dollar spot fungicide screens I have run
for some of you in the past, I am going to attempt to screen
for resistance in these strains of anthracnose myself, or try
and find another lab that can do it. If you have any anthracnose
you would like to screen, give me a call and send me a sample...
Dollar spot has been the other big story in northern
Illinois. It appears that we are not going to get out normal
summer lull and may run into a disease pressure year much like
2000 (see figure below). This has put a major strain on some
fungicide budgets as one superintendent exclaimed," I am
6 K over budget because of dollar spot just in the last month!".
With the mild temperatures expected to continue, the dollar
spot doesn't look to slack off any time soon either. We have
many complaints of fungicide control failure for dollar spot
coming in this year, but this may be due to an this year's extremely
conducive climate and not necessarily a fungicide resistance
problem. Like the anthracnose, I will be screening dollar spot
isolates for resistance again this fall, so if you are curious
give us a sample.
Figure 1: Normally dollar spot experiences a summer lull
in activity, which is why we wouldn't normally prescribe a long-
lasting systemic fungicide at this time for outbreaks, because
you wouldn't get the bang for the buck so to speak. This year,
however, may be much like 2000 when the dollar spot severity
did not curtail during the peak summer months.
Type II fairy rings have been around for a while
but have become a nuisance on many greens throughout the Chicagoland
over the last week or two. These fairy rings cause a lush ring
of dark green grass caused by nitrogen released as the fungi
decompose organic matter in the thatch layer beneath. The fungi
may also produce basidiocarps, or mushrooms, on greens after
a rainstorm. The most common of these are the puffballs caused
by Lycoperdon sp. The best thing to do for these fairy
rings is try and mask the symptoms with fertility, and manually
remove the mushrooms.
Conversely, in southern Illinois, many are calling
this the worst year for fairy rings they have ever seen. These
are of the type I variety where a ring or zone of dead grass
is present in advance of a zone of green lush grass. It is not
completely clear why this ring of dead grass is present but
the most likely reason is that fungal mycelium is builtup so
high that it renders the soil hydrophobic and the plants die
from moisture or heat stress (many of these fairy ring are associated
with LDS symptoms as well). Other reasons or related factors
may include: 1) nitrogen levels become high enough to be toxic;
2) the fungus may produce toxic levels of hydrogen cyanide;
3) roots may be infected and shut down by the fungus; or 4)
weakened plants are killed by other pathogens or stresses. Unfortunately
control options for fairy ring are still quite limited. Severity
of symptoms can be reduced by mechanically removing excess thatch,
core aerification (spot aerifying trouble areas), water-inject
cultivation, and use of a turf wetting agent, at one or two
week intervals during dry periods. Daily syringing of LDS is
necessary to keep turf alive during hot periods, and some managers
use a water injection fork on bad areas. Fungicides with activity
against basidiomycetes (ex. flutolanil) have also been shown
to reduce the severity of LDS.
The warm weather pathogens have been present in
some areas but not really damaging yet because of the mild weather
(except for southern IL!). Pythium was reported in Bloomington
and Springfield following Sunday and Monday's warm weather,
but have been limited due to cool nights since then. There has
also been some spotty Pythium outbreaks in the last two weeks
throughout Chicagoland, but these have been on newly seeded
areas and have been more of a crown and root infection than
a true cottony foliar blight that we'd see on an established
turf. Interestingly, Pythium root rot is not normally a problem
in older plants (over a year or two old) as adventitious roots
and a true fibrous root system begin to function efficiently.
Insects:
The Ataenius activity has slacked off, (because
most areas have been treated), but the worm activity is back
on the rise. Several cutworm sightings have been reported in
the last few days, as well as the first report of sod webworm
activity from a course in Chicagoland. Sod webworm larvae cause
damage to turf when the caterpillars feed on turf blades from
silken tunnels formed down in the thatch. One of the first signs
is the larvae will push up little mounds of sand on the greens
while making tunnels. Much of the feeding that eventually occurs
is only on the leaf blade and not the crown, which makes this
one of the least damaging turf insects, but it does still stress
the plant considerably and on lower cut turfs can cause considerable
browning and thinning. Most insecticides that control cutworm
will also control webworms, but water the application in (to
try and get in those tunnels), and apply later in the day if
possible since they feed at night.
Japanese beetle adults are running rampant throughout
the region now, although peak emergence may not happen in northern
Illinois for another week or so. All areas should be aware of
and scout for damage to ornamentals, as the earlier you can
prevent or limit outbreaks, the more likely the beetles will
go to another plant (or your neighbor's yard!). See below for
a table of trees and ornamentals that are some of the favorite
snacks of JBs.
Ornamental plants highly susceptible to
feeding by Japanese beetle adults.
|
Japanese maple
|
Norway maple
|
|
Gray birch
|
Horsechestnut
|
|
Black walnut
|
Sassafras
|
|
American elm
|
Althea
|
|
London planetree
|
Rose
|
|
Black cherry
|
Crab apple
|
|
American mountain ash
|
Lombardy poplar
|
|
Pussy willow
|
Lindens
|
Moss and Crabgrass:
The mild, moist weather has caused many moss outbreaks
on greens throughout Chicagoland. Some success for moss problems
has been reported with fungicides such as Junction (copper hydroxide
and mancozeb), Daconil, Dithane, Fore, and Iron Sulfate, as
well as the baking soda and Dawn mixtures.. One notable tank
mix for moss control supplied by Wayne Otto (via Les Rutan@Crystal
Tree) is Spotrete @ 4.5 oz/1,000, Echo (90% A.I) @ 5.7 lbs/A,
& Dithane @ 4 oz/1,000 applied on a 2 week schedule. A lot
of chemical, but some guys swear by it.
Crabgrass is really starting to become a problem
throughout some areas of northern Illinois. We have had good
success with quinclorac (Drive) on some of our problem areas,
but fenoxaprop (Acclaim) is also reported to have good post
emergent control.
+++++++++++++++++++++++
Thanks for your support of this, as well as all
of our research programs,
Randy
Kane
CDGA
Director of Turfgrass Programs
Midwest Golf House
11855 Archer Ave
Lemont, IL 60439
630-257-8126
Lee
Miller
CDGA
Manager of Turfgrass Research
Midwest Golf House
11855 Archer Ave
Lemont, IL 60439
630-257-2005 x.106
