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Poa Heat Stress pictures.
(click image to enlarge.)
Weather Summary and Outlook
After a slight break in the high temperatures Aug 2-3, more heat and humidity moved back into the area yesterday and today (Sunday - Monday).
The forecast calls for continued hot and humid conditions through at least Wednesday or Thursday, with possibly a cool break by the weekend.
The combination of temperatures in the low to mid 90s and dew points in the 70s will give us heat index readings well over 100F for the next few days. We are accumulating quite a few 90+ days for the 2001 season, and turf conditions across the area are starting to show the strain, especially the weaker Poa species, especially P. annua and P. trivialis; (see photos above).
The Chicago area had 9-10 days above 90F in July, and 19 days with daily high temps reaching at least 85F.
Meanwhile, central Illinois had as many as 16 days of 90 or above (depending on location), and 24 of 31 days over 85F.
Unfortunately, August is shaping up to be a hot month as well.
We haven’t had a lot of heat in August since the summer of ’95 (in 1999, there was only 1 day >90 in Chicago, 2 days in 2000).
The average over the last 15 years is 4 days in August with temps of 90 or above.
We will be well past that average by the end of this week.
This year, it seems the transition zone is moving a little farther north...
Hang onto your hats! Zoysia grass anyone?
Diseases
Pythium blight and brown patch outbreaks are now commonplace in isolated areas (eg low spots on fairways, some protected tees or greens).
We are receiving many reports of reduced disease control and repeated fungicide applications in the most susceptible areas.
Pythium is also running wild in some longer grass areas (roughs, tee/green surrounds, etc) that are being left untreated.
The most damage is occurring where these areas contain a lot of fine fescues or perennial ryegrass.
You may want to consider spot treating some of these rough areas if it is likely that people/machine traffic could track spores of Pythium onto more valuable turf.
Complaints about high temperature fairy rings continue to mount.
Also, there are more reports of turf dying off quickly around the outside edge of the ring during high temperature stress.
This symptom can sometimes be confused with a summer patch or other patch diseases, or possibly a Rhizoctonia disease.
However, fairy ring fungi do not infect the plants, and only cause turf injury indirectly by releasing toxic substances as they decay organic matter in the thatch layer (eg hydrogen cyanide!).
Control of the fungi or inhibition of the ring symptom is difficult, especially if you are expecting a quick turn-around.
Many superintendents are trying a fungicide + wetting agent tank mix (eg Prostar + Primer) with variable results short term, some more promising results have been observed after a week or two.
Insects
The most recent round of cutworm larval activity on fine turf may have peaked last week.
Many superintendents reported treating for cutworms on areas that don’t normally require an insecticide (eg tees), and also reported large numbers of dying worms coming to the surface soon after treatment.
Japanese beetles are still feeding on their favorite plant morsels, and will continue to mate and lay eggs in irrigated turf.
The larvae will get big enough to attract skunks and raccoons in early to mid-September with the other scarabeids.
We will see how the heat and some of these heavy rains affect the long term activity of the newer grub insecticides.
Weeds, etc: Some of you may see algal blooms now or in the next few days, especially if you were in the track of the heavy rain last Thursday.
Saturated turf conditions (combined with our heat and humidity) can cause areas to thin out, and allow algae to gain a foothold.
If you have a developing algal problem, try to dry out the wet areas if possible, and perhaps open up the surface to some oxygen (but we don’t recommend aggressive spiking or coring during this hot spell).
YOUR FEEDBACK OF OBSERVED PEST PROBLEMS IS IMPORTANT
RSVP as usual to pestalert@interactiveturf.com.
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