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Landscape and Turf Maintenance By Bruce Carmichael Turf Pest Management Q&A F or an overview of diseases, weeds and insect pests that are impacting turf this summer, as well as how to deal with these challenges and also prepare for the fall and winter months,Landscape and Irrigation recently spoke with Michael Agnew, Ph.D., senior field technical manager at Syngenta. L&I:What turf diseases, insect pests and weeds are landscapers dealing with this year, and what might be in store the re- mainder of this summer based on weather forecasts? Agnew: I use history as a good barom- eter of the future. Last year’s weather con- ditions — where we had one of the worst summers in a long time as far as heat and rain — has pretty much been mimicked by early high temperatures and rains. There has been greater devastation due to heavy rains, flooding and tornadoes. This has led to saturated soils. A significant amount of rain in the spring can be a precursor to several disease, weed and insect issues. Often people haven’t been able to get out onto the properties to make needed applications, because it was too wet. In those cases, some of the products they ulti- mately applied may not have stayed in the soil and moved below the zone of germi- nation. As such, I expect to see several fail- ures on pre-emergent herbicides, simply because the weather conditions set it up for that. With insects, it depends on how wet it was. If it was really wet, turf managers may see some mortality of grubs. All living or- ganisms require oxygen to survive, and sat- urated soils leave no room for oxygen. Across the transition zone — from Kansas City to Maryland — it is pretty consistent that you get some grub activity on a yearly basis. The type of grub will vary upon your location. Surface feeders are not perceived as being as severe of a problem, but the blue- grass billbug is one that can be pretty dev- astating. I’ve seen entire sod fields wiped out within days following an infestation. When it comes to disease, brown patch is likely to be the number one pathogen — especially with tall fescue or ryegrass. Those species are very susceptible to infec- tion by brown patch. High soil moisture, high humidity and high temperatures are needed for disease activity. If you have continued wetness for 10 hours on the leaf surface, and you have temperatures above 85 degrees, that’s a perfect storm for a diseases like brown patch and Pythium blight. These two dis- eases can happen at the same time, and usually it takes two different fungicides to control them. So you have to have the right fungicide down. In the south, one thing I would be con- cerned about is a leaf spot problem on bermudagrass, because there is some root rot that can happen when cool wet weather goes to a warm, dry period. Another disease that may be possible this summer is summer patch on species like Kentucky bluegrass, annual bluegrass, and fescues — especially in areas that are prone to drought quickly, such as hillsides. The best way to treat for these diseases is preventive. Areas that are injured by sum- mer patch are sites to consider for intro- duction of tolerant species. Saturated soils can lead to root systems that are compromised. The lack of oxygen can lead to a weakened root system that is High soil moisture, high humidity and high temperatures are needed for disease activity. 16 Landscape and Irrigation July /August 2011 more prone to disease, especially when you experience the higher temperatures. In a typical year, if you can control Pythium blight and brown patch you can get through the summer in pretty good shape. L&I: Is curative treatment preferred over preventive? Agnew: Early curative is fine. The key is to look for symptoms, and if you are using a scouting system that is combined with monitoring of the weather condi- tions, treatment applications are still pre- ventive. There are predictive models that use weather conditions that give you ample warning to schedule an application. This type of application can be just as effective as making applications every 30 days. Late curative applications can be consid- ered post-mortem application — the damage has been done. Applications at this point are to prevent any further spread. If turf damage has been done, now is the time to start thinking about seeding in the fall. L&I: What recommendations do you have to limit the spread of disease? Agnew: Mowing is one of the main ways of spreading diseases such as leaf spot, Pythium, brown patch and dollar spot. The mowing process is essentially an inocula- tion process because you are transferring infected leaf blades to otherwise healthy leaf blades. One way to prevent spread from one site to another is to clean the mowers between job sites. If you believe there is an issue, hose off the blades and make sure they are clean before you go to other sites. Another way to reduce spread is to use a PGR [plant growth regulator] to slow down the growth. This reduces the need to mow as much. PGRs can be used in com- bination with fungicides as a good way to control diseases in the turf. The reduction www.landscapeirrigation.com