It was a humid week in Illinois. However, not everyone got the rain they needed.

My first summer in Illinois is slowly winding down. This past Tuesday the date of the calendar read August 15th. Supposedly this is a long awaited date that signals the ease into fall. Those that were expecting a quick reprieve from summer probably weren't satisfied this week.

The very next day (August 16th) temperatures throughout much of Illinois rose into the mid to upper 80’s with very high dew points.

August 16th felt like mid-July. Weather data courtesy of weather underground.

In this region, dew points above 70 degrees can feel extremely muggy. The max dew point observed in Effingham was 78 degrees on August 16th. The mean humidity throughout the entire day was 85% at this location. Not only was this weather difficult to work in, but it was an outdoor petri dish for many of our fungal pathogens.

Afternoon rain showers we felt in the northern part of the state this week.

The warm-humid area finally broke as frontal system swept in and brought rain showers with it.

7-day precipitation totals across the region. Courtesy of NOAA.

Areas in the northern and southern part of the state received upwards of 1–2 inches of rain this week. Central Illinois, which is in need of rain, was not able to cash in this week.

Current drought status across Illinois. Courtesy of the National Drought Mitigation Center.

Areas in central Illinois have been abnormally dry for quite some time. Non irrigated roughs are brown and many golf courses are now mowing them less. Although it is not indicated on the drought monitor, there are areas in northern Illinois that are a little dry as well. Far western suburbs and areas to the south and southwest side of Chicago are fairly dry.

This week much of Illinois was very humid with high dew points. This kicked up quite a few diseases and other pests.

Weeds

Goosegrass emerging in thin areas.

I was asked earlier this week on what ‘southern pests’ seem to be creeping north in our area. Goosegrass is a candidate weedy grass that seems to be becoming an increasing problem in the northern portion of the state.

Many facilities in the far northern areas of the state do not make preemergence herbicide applications that target crabgrass. Those that do make a herbicide spray, usually will only make one application. Goosegrass tends to germinate well after crabgrass. Meaning, those that make single preemergence sprays for crabgrass, may not have enough residual activity to prevent goosegrass from germinating later in the summer.

Without competition, summer grassy weeds can get quite large.

The best way to prevent many grassy weeds is to have a dense healthy stand of turf. As seen in this picture, grassy weeds can get quite large during the summer months if there is no competition for space and other resources.

Weed encroachment on old sod piles that were never used.

I also saw some weed encroachment on older sod. Promoting a healthy turfgrass environment would have reduced this weed population. It is best to unroll sod and lay it green side up.

Insects

We are on the lookout for armyworms this time of year and other grub activity. I also observed quite a few black turfgrass ataenius adults running across putting green surfaces this week as well.

Cicada was resting on putting green turf.

I am also seeing more and more cicadas. This guy was resting on a putting green surface and I wasn’t sure if he was alive. I poked him and he flew off. It still makes me wonder why he thinks this is a good spot to be at. Considering the number of cicada killer wasps that are buzzing around right now.

Monarch butterflies can often be found near milkweed plants.

It seemed to be a good week for the monarch butterfly. I found several of these at the Midwest Golf House in various milkweed gardens. It is more difficult than you would expect to photograph these beneficial insects.

Diseases

Dollar spot pressure was extremely high this week in the Chicagoland area. I noticed some dense fog on Tuesday, Wednesday, and Thursday morning. Couple the really high humidity with longer nights…and you get a dollar spot explosion.

We are learning in many of our research trials the difference between controlling dollar spot and suppressing dollar spot. Not many chemistries can achieve 21 days of dollar spot control on fairway turf if heavy disease pressure occurs at the tail end of that spray interval.

More than 200 dollar spot infection centers were observed this week in select plots.

On putting green turf, we also observed dollar spot activity in treated plots on 14-day intervals. Although, the treated plot on the right is still fairing much better than the nontreated check on the left. We look forward to wrapping up our summer trial work and providing those results to you all in the coming weeks.

Dollar spot is chipping away at creeping bentgrass within a zoysiagrass practice tee.

Sometimes dollar spot may be beneficial. We have a zoysiagrass tee box at the Midwest Golf House. Zoysiagrass is much less susceptible to dollar spot this time of year compared to creeping bentgrass. In this case, the dollar spot is helping to chip away at the bentgrass.

This week we also observed brown patch and Pythium blight activity. Brown patch was observed on a creeping bentgrass putting green and was difficult to see. The use of polarized glasses can help with scouting.

Brown patch was much easier to detect this week when we incubated field samples after inoculating these cup cutter plugs.

Pythium was observed this week in the form of damping off. Damping off can be a severe disease of new seedlings. There are many new seeding efforts around Illinois due to flood damage.

Matted down greasy leaves are a symptom of damping off.

A symptom of damping off is the sudden appearance of greasy leaves that do not stand upright compared to healthy unaffected nearby seedlings.

In the early morning, aerial mycelium can be observed in seedling areas.

Fortunately there are signs of damping off that also aid in the diagnosis. Aerial mycelium can be observed in the early morning after a humid night. Damping off caused by Pythium or Rhizoctonia can kill seedling plants very quickly.

On mature, existing turf, the anthracnose train keeps on rolling.

Putting greens affected by anthracnose usually suffer considerable decline during summer months.

A closer inspection of affected plant material reveals the presence of black acervuli and setae on the plant.

Black acervuli and setae can be observed on plants affected by anthracnose.

One of the reasons why anthracnose is difficult to control is how resilient these fungal structures are. They can tolerate a wide range of temperatures and they can successfully overwinter each year. Another reason is that these fruiting structures house a lot of spores.

Inside the acervuli are millions of conidia.

These spores are called conidia and can spread rapidly through splashing rain droplets and mechanical traffic.

Looking ahead

Expect high dew points on Tuesday of this week. Courtesy of pivotal weather.

The next bout of warm-humid weather should be on Monday-Wednesday. This should flare up some of our summer-time diseases. And again, damping off on many of our new establishments will remain a concern.

However, looking further out, a seasonably cool period should be widespread throughout the region to end the week.

Something else I have been noticing as we continue to move forward in the season. Shade patterns seem to be increasing as the sun angle is slowly going down.

Shade patterns are increasing due to a lower sun angle. Expect to see more leaves fall in the coming weeks.

It won’t be long until we get the leaf blowers out.

Dedicated researchers and turf pathologists working for golf course superintendents in the Chicago area.