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Here is your Turf IPM update for the second week of August, 2000, covering pest problems for Illinois golf courses and sod producers.
Moderate weather continues to be the big story for this year, as the Chicago area and most of central Illinois has yet to officially record a 90 degree temperature reading.
Decatur reported a high temp of 91 F on Aug 9, by the way, and has had a grand total of 3 days over 90 for the year.
The forecast for the upcoming week is for somewhat higher temperatures and returning high humidity, which could lead to scattered incidence of Pythium blight and brown patch - so don't let your guard down just yet!!
Diseases
The continued warm and humid conditions in central and NW Illinois will lend itself to developing epidemics (?) of Gray Leaf Spot on perennial ryegrass fairways and roughs.
There have been numerous reports of GLS in the mid-Atlantic region, and we are starting to see some activity in central Illinois, Kentucky, and elsewhere.
A key now is to not confuse GLS symptoms with Pythium or brown patch.
If Pythium or brown patch is active, you should see signs (cob-webby mycelium) of the fungi moving from leaf to leaf early in the morning, or when relative humidity remains high through the day.
If small, scattered patches of rye are thinning or collapsing (reddish brown leaves) and there is little or no mycelium, look for Gray leaf spot lesions on leaves, or the characteristic "fish-hook" wilting and twisting of the youngest leaf tips.
Misdiagnosis of a developing problem on rye can lead to big problems if the WRONG FUNGICIDE is applied and no control is realized (plus you can be wasting a lot of $$$$)! Dollar spot continues to be the disease of 2000 however, with a lot of red thread and rust thrown in for good measure (on lawn height grasses).
Control of dollar spot on golf course fairways has been a headache for many superintendents this year - for several reasons.
Here is MY OPINION: 1) fairways are underfertilized; 2) fungicide application rates on fairways are too low for the amount of disease pressure we are seeing; 3) frequent rain and high humidity are shortening residual control times even if adequate rates were applied; 4) there could be field resistance developing to the fungicides you are using - esp. if a DMI.
As I mentioned previously, I am collecting strains of dollar spot fungi from around the area that may have developed some fungicide resistance ("tolerance").
I hope to do some in vitro screening in the lab this fall/winter to see if I can document that increasing fungicide tolerance is becoming a more widespread problem.
Also, I have a small dollar spot fungicide trial out at Cantigny, to see if the fungi there are resistant to benzimidazole or DMI fungicides, and to demonstrate (once again?) the added benefits of tank mixes which include foliar N.
Insects
Are Japanese beetle adults finished feasting on your little leaf lindens? If so, they are probably off to lay eggs in nearby irrigated bluegrass to initiate the fall crop of grubs (and digging by the animals that are looking for a tasty treat!).
You can start scouting for annual white and Japanese beetle grubs over the next few weeks, with a level of about 10 grubs per square foot needed to cause turf loss.
Phil Nixon reports that annual white grubs have hatched in central IL, and larvae are about 1/4 inch long.
Merit and Mach 2 can still be applied for control, but it is getting late!!!
There is a good overview of white grub activity and a review of Gypsy moth problems in the August 9 Home Yard and Garden Pest Newsletter at:
www.ag.uiuc.edu/cespubs/hyg
Be sure to check it out!
Weeds
I continue to receive inquiries and comments about moss occurrence and control problems on greens.
A few superintendents have reported to me that the only approach that seems to work long term is the "witches brew" from a couple of years ago, which contains Subdue 2E and a wetting agent (Lescoflo or others?).
Applications of Fe or K have been reported to help in some cases, and Dawn Ultra sprays have worked sporadically as well.
But it has been a tough year for moss regardless, probably because of the weather.
I continue to receive reports of crabgrass and a number of broadleaf weeds such as clover and plantain.
Also, I am still hearing complaints about Poa annua that is continuing to produce seed through early August.
Oh well?
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