Scouting Report: July 9th
The dog days of summer are here in the Midwest region. Historical averages suggest that we are now entering the hottest time of the year.
The dog days are a reference to the star Sirius. Sirius is the brightest star that included in the constellation Canis Major or “greater dog”. During summer, the star rises and sets with the Sun. Ancient Greeks believed this star was responsible for sweltering heat and humidity. It was known to cause lethargy and fever.
In turfgrass, this is also when we observe our turf acting lethargic. This time of year is when most of our grasses are prone to a number of maladies and diseases. Many of us got an early taste of the hot/humid environmental conditions earlier this week.
Air temperatures scooted to near 90 degrees F this past Thursday in many parts of Illinois. This heat was accompanied by very humid air and rising dew points that approached 70 degrees. Unlike some of our earlier heat waves, we weren’t rapidly losing soil moisture during this time.
Controlling our own moisture was something many of us were able to do this week. Spotty showers and thunderstorms seemed to be all around us this week in Illinois. However, the thunderstorms that did pop up did not hold together very long across the state.
Some of these areas that have stayed dry this week have actually been on the dry side for a few weeks. A couple of abnormally dry demarcations are now expressed on the latest drought monitor.
Being on the dry side is just fine for managing golf courses. We should be okay with some browning in the roughs and a couple of hot spots in the fairways. I should have played some golf this week to comment about playability from experience. But, from what I have seen, fairways are firm and golfers are enjoying excellent conditions.
Being dry may also have advantages as we head into next week. Environmental conditions are likely to be hot and humid with chances of precipitation on most days. I’ll comment on what that could mean moving forward, but first I will recap this week’s pest reports.
Weeds
Areas that stay wet are seeing more silvery thread moss pop up on low-mow areas such as putting green surfaces.
This nursery green had a relatively uniform moss population. This uniformity has given rise to research opportunities. The CDGA Turf Program is evaluating various experimental products for their effectiveness at reducing moss populations.
We hope to share results of this ongoing investigation towards the end of the season. In the meantime, here is a nice example of herbicide induced epinasty on dandelion.
Insects
Cutworm activity was observed this week in the Chicago area. These pin hole sized openings are an indication of their presence.
Last week I observed Japanese beetles in the Chicago area. This week I observed masked chafers. Control programs in turfgrass systems should be aimed at the white grubs. I suspect that applications to control white grubs should happen earlier than usual this year. On ornamental trees, control of the adults are occasionally warranted.
Humid mornings have also resulted in greater visibility of spider mite webs. These webs can mimic mycelial production from disease causing organisms.
Diseases
The causal organism for dollar spot fluffed up nicely on Thursday morning. I say nicely because it was in the confines of our research plots. In this particular trial, we are testing various SDHI fungicides at low spray rate volumes (0.5 gal/M) compared to higher spray rate volumes (1.5 gal/M).
Bipolaris leaf spot is snaking its way past many fungicide programs recently. This disease may not be controlled effectively by contact fungicides or phosphite materials. This disease can be difficult to scout and can ‘pop up’ suddenly on putting green surfaces.
This disease has been predominately diagnosed on ‘A series’ creeping bentgrass putting greens. The host specificity remains unclear, however. Other cultivars of creeping bentgrass or stands of annual bluegrass are often cited to be susceptible to this disease as well.
Slime molds are popping up across Illinois. Slime molds are not technically a disease as the casual agent doesn’t infect the host. However, that doesn’t mean it can’t colonize the surface of plant material.
Sometimes slime molds colonize turfgrasses and broadleaf weeds simultaneously.
A close up examination showcases the small pustules of material that encompasses the turfgrass leaves.
Landscapers are also familiar with this pest.
Slime molds can also colonize mulch beds. The appearance of this organism in mulch beds has also given rise to its alternative name: Dog vomit fungus.
When conditions are ripe, slime molds can also appear ‘gooey’.
Maple issues
A red maple tree has expressed symptoms of nutrient deficiency as evident by interveinal chlorosis. In this case, the maple was surrounded by roadways and walking paths that were heavily salted this winter. In this area of the country, manganese deficiency can be rare…but can happen.
Silver maples in the Chicago area have also expressed symptoms of tar spot. The pathogen that causes this disease induces black spots on leaf material. This isn’t considered a serious disease. However, it can cause premature leaf drop.
Looking ahead
The team at Thermodynamic Solutions has commented on the potential environmental conditions that could impact turfgrass managers throughout the Midwest.
Extremely high dew points may be likely throughout much of the state into next week. Diseases such as brown patch and Pythium blight can be opportunistic during times of high heat and humidity. Additionally, it is very easy to over-water turf when it ‘feels hot’.
