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Weather Update
It seems that no matter how hard they try, weather forecasters "get it right" for the next 48-72 hours; but beyond that period they are guessing as much as we are.
There was a slight deviation from last weeks predicted moderate weather week, as a bubble of hot, humid air slipped to the north from the gulf/plains region starting July 7.
Hopefully, the predicted cool down for tomorrow and the rest of the week will actually happen.
In the mean time, we are suffering through daytime highs in the upper 80s to low 90s with high relative humidity.
Saturday evening the radio weatherman informed me that it was 85F with 85% relative humidity at sunset.
Overnight relative humidity readings have ranged between 80-90+ % for the last 3-4 nights.
Of course this kind of weather pattern shifts our focus to the fungal diseases Pythium blight and brown patch, so be sure to check your indicator areas (Hot Spots) for early signs of outbreaks.
Diseases
As warmer, drier air moves in for the summer, the incidence of fairy rings will continue to increase.
In the past, we considered fairy rings to be nothing more than a nuisance, since the presence of a visibly darker green ring didn’t cause any concern for the health of the turf, and could be used as an indication of low N or Fe (or other micro) fertility.
Nowadays though, fairy rings are becoming more than a nuisance - for at least two reasons.
First, in some cases the outer, active ring of the disease actually wilts or turns brown under stress, leaving a dead ring of grass that looks ugly and is sometimes mistaken for other diseases.
Second, fruiting bodies of some fairy ring fungi are becoming more disturbing, especially on greens where the fungal body can deflect the roll of a putted ball.
Fungi that produce "puff ball" type fruiting bodies (especially Lycoperdon species) are becoming more common on greens, are very difficult to control, and appear to contribute to the development of localized dry spots.
We have had a few reports of minor Pythium disease occurrence in both central Illinois and the western Chicago suburbs.
Weather-based disease prediction models are kicking in with warnings for Pythium and brown patch, because of the high temperature range and prolonged periods of high dew points and leaf surface wetness.
Since the weather forecast indicates much cooler, drier air taking over the northern half of the state by tomorrow and Thursday, we recommend scouting hot spots before spraying.
It takes several days of hot humid weather to get a Pythium or brown patch epidemic going - if you weren’t already "covered" for these diseases with a targeted preventive application, there is little point treating now unless disease is active in your indicator areas (remember: IPM involves scouting and targeting pesticide applications!).
Another disease that is becoming active now is anthracnose.
We have seen disease symptoms on both Poa annua and creeping bentgrass in the last couple of days.
It interesting to note that the symptoms are very different on each turf species, Poa turns bright yellow to reddish brown in small, dime-sized patches ("freckles in clusters"), whereas bentgrass gradually thins in more diffuse, stressed patches that strongly resemble a localized dry spot.
Also note that where you have anthracnose on Poa annua, intermingled patches of bentgrass will be unaffected (uninfected?); and where you have patches of diseased bentgrass the Poa will be healthy.
For whatever reason, the anthracnose strains that attack Poa do not strongly attack bentgrass, and strains that attack bent generally do not attack Poa.
Also remember that anthracnose is a low fertility favored disease, and that tank mixing some soluble N with a curative fungicide treatment increases the level and speed of control significantly.
Note also that dollar spot will become active again as we cycle through from warmer to cooler weather.
Last week’s cooler, drier air slowed down development of this disease, but dollar spot could really take off this week if temperatures remain moderate and some humidity returns.
We have observed increasing dollar spot activity on our test plots the last week or two; so if you are on the back end of a treatment interval for dollar spot, you should be watching for "break-through" and preparing for the next preventive/early curative application.
Don’t stretch control intervals too long - that is what caused a lot of the problems last year.
Once dollar spot becomes entrenched it becomes much more difficult to control.
Insects
Adult Japanese beetles are flying over most of the infested areas of the state by now.
Watch the Linden trees and other favored species for feeding activity.
If you are in an area that has high levels of JB infestation in recent summers, you should consider treating key trees and shrubs soon to deter feeding injury.
Also note that feeding injury on plants seems to attract more beetles to the site, so reducing feeding injury early on would be the best approach.
Adult moths of sod webworms are flying in large numbers now also.
In general, feeding by sod webworm larvae on fairway or rough height turf does not cause significant injury (unless flocks of birds are digging around for the larvae).
However, damage on putting green turf can be significant if left untreated.
Injured areas are quite distinctive since the larvae make a small, sand lined tunnel just under the surface of the turf and feed on leaves nearby.
Injury from sod webworm larvae will likely become visible in 2-3 weeks.
Fortunately, insecticides that control black cutworm also control sod webworms.
Weeds
Complaints about clover invasions of fairway turfs continue.
Why has clover become a chronic weed problem on fairway turf in the Midwest?
There are probably numerous reasons, but it all boils down to biology and competitiveness of the clover plants.
Clover grows well in the cool, wet conditions of early spring and gains a foothold in bent/poa fairways at this time.
Clover tolerates close mowing easily, and continues to flower and set large numbers of seed at fairway height from May through early September.
Clover has a great competitive advantage at low N fertility levels! Clover is in the legume family and, if nodules form on roots, can symbiotically fix N from the atmosphere.
Clover can rapidly colonize weak areas in bent fairways where plants have been stressed or thinned out by traffic, localized dry spots, or diseases (the best example is take-all patch).
YOUR FEEDBACK OF OBSERVED PEST PROBLEMS IS IMPORTANT - especially at this time of year, when diseases and insects are becoming more active.
Please respond with your observations to pestalert@interactiveturf.com so that we can build our pest activity data base and report those pest outbreaks back to our readers.
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