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Weather Summary and Outlook
After five hot and humid days in a row (July 20-24), we caught a nice break the past few days as temperatures dropped into the mid to upper 70s for daily highs and dew point (relative humidity) numbers eased off as well. This cold front brought some needed rain to many areas in northern Illinois, and some areas received several inches of rain in quick moving storms. It is not clear how beneficial this type of precipitation is, but we will take what we can get! Unfortunately, summer isn’t over yet. Another “hot dome” of humid air is coming back over the region beginning today (Sunday), and temperatures and heat indices are expected to climb back into the 90-100+ range for the next 5-7 days. There have been many complaints about the difficulties in maintaining uniform soil moisture levels when we go into (and out of) hot and humid weather patterns. Most superintendents have commented that they greatly reduce irrigation during hot and humid periods, but they still have to watch the turf closely to prevent heat or drought stress. This can become even harder when we get sudden heavy rains followed by cooler temps and drastically lower humidity. Last week (eg Thur and Fri), it was typical to find low areas in fairways that were too wet, while just a few feet away turf on humps or slopes was dry and starting to wilt again.
Diseases
Many of you are saying "adios" to some Poa annua and Poa trivialis after this recent heat wave. We didn’t have to deal with too much Poa decline last summer, but this year the weather is much more average for Illinois, which includes these hot/humid spells that can take out the Poa. High traffic areas on greens and fairways are always the first to go - look for tire marks or mower patterns in stressed traffic areas (around cart paths, approaches to greens, green collars). Many times fungi are associated with summer decline (Rhizocs, summer patch, anthracnose), and turfs that are under a preventive fungicide program often fair a little better. But as the accumulated stress builds, more Poa will be saying adios to you, too!
As expected, high temperature foliar diseases like Pythium blight and Rhizoctonia brown patch hit the region last week, even cooler north shore courses. If you made preventive or early curative treatments for these diseases last week, you must continue to monitor the indicator areas for reoccurrence of the fungi. Breakthroughs may be possible if you experienced some of those heavy rains last week after a fungicide application - heavy rain or irrigation often shortens fungicide residuals. In central Illinois, Pythium and brown patch disease pressure has been high enough that fairly short residual control is occurring and the most susceptible areas have had to be retreated multiple times (!). Here too, heavy or frequent rains are reducing the residual length of control for certain fungicides.
The summer heat is also bringing out more fairy ring problems; mushrooms and puff balls were popping up all over last week. Some of these fairy ring fungi (whether or not they actually cause a ‘ring’) also lead to development of localized dry spots - especially the puff ball fungi in the genus Lycoperdon. Some moderate success has been reported in treating these problems with fungicide/wetting agent combos, most notably Prostar and Primer.
GRAY LEAF SPOT WATCH
For those of you growing ryegrass in central IL, there have still been no confirmed outbreaks of GLS through 7/28 (that we know of anyway). We have received some suspicious samples in the lab, but so far we have found only Helminthosporium types of leaf spot. Stay tuned….!
Insects
It’s not only getting hot out there in turfland, it is also getting buggy. Almost every response we received to update #9 mentioned increasing activity of cutworms, and the inevitable bird damage that comes with the lascivious lepidopteran larvae. Scattered reports of Japanese beetle adults continue to come in as well. In the last week or so, we have not heard of any more damage from Ataenius grubs however. Most of the cutworms are being treated with Dursban, but there are several other effective insecticides out there, including Dylox, Tempo, Deltaguard, and Sevin. A few people have reported using Merit for control of Jap beetle adults on trees and shrubs, especially in a tank mix with an older contact (leaf surface) insecticide. Merit has some systemic activity and may stick around a little longer.
Weeds
The heat and humidity also seems to bring out the best of our C-4 grassy weeds, like crabgrass and goosegrass. If you are contemplating a post emergence herbicide application (eg with Acclaim or Drive), be sure to read the label for species sensitivity and heat effects - don’t burn up the turf trying to control the weeds! Algae and moss problems are increasing again as we get further into the season and the heat and moisture are building. Weak, stressed turf is much more susceptible to algae invasion at this time, so be alert for these invaders. Algae and moss are both difficult to control once established and require different approaches to try to correct the situation. On the moss front, moderate success continues to be reported with the new product Terracyte, but we are not sure how safe it would be to use in this heat.
YOUR FEEDBACK OF OBSERVED PEST PROBLEMS IS IMPORTANT
RSVP as usual to pestalert@interactiveturf.com.
We received very good response to the last newsletter, the pests are out there!
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