Field Observations Summer 2015 Gordon Kauffman III, Ph.D. – Technical Manager
July 27, 2015 – With summertime in full swing, we thought it would be helpful to publish a report from the field highlighting the challenges and conditions that turf mangers are currently facing in the U.S. and parts of Canada. This report falls on the heels of our June technical bulletin documenting the importance of Grigg Brothers’ preventative nutritional integrated pest management programs – including the use of phosphite and fungicide to manage pests, notably pathogens, effectively (http://gri.gg/summer1). Weather, of course, plays a pivotal role in determining the extent of plant stress - and ultimately pest pressure. Each golf course is different; therefore careful observation remains necessary to address and provide the required inputs to maintain turf vigor. Additionally, using history as a guide and careful planning are important to develop a guideline for success. Most cool season turf managers have dealt many pests already, including annual bluegrass weevil and white grubs, dollar spot (Sclerotinia homeocarpa), anthracnose (Colletotrichum cereale) and general turf decline due to poor drainage, air circulation, or shade. Dealing with the latter requires consistent and often aggressive cultivation, topdressing and tree pruning/removal. The weather has been dry in the west, hot in the south and southeast, Figure 1. Brown patch on a creeping bentgrass putting green (June 25, 2015) and wet in the midwest and northeast. Interestingly, May was dry in the midwest and northeast and then turned excessively wet in June and into July – essentially feast or famine. Currently, where wet conditions have persisted, high day/night temperatures and high humidity has increased the risk for diseases such as brown patch (Rhizoctonia solani), summer patch (Magnaporthe poae), take-all-patch (Gaeumannomyces graminis) on creeping bentgrass and pythium blight (Pythium spp.) to flare up and become problematic (Figure 1) (Smiley et al., 2005). Dollar spot activity started earlier in the summer, but persists with excessive leaf moisture and lower than average soil moisture (Figure 2) (McDonald et al., 2006). Control can be optimized when applying fungicide and nutrient to turf without dew and in low water volumes (*McDonald et al., 2006). Additional research suggests the importance of foliar nutrition and rotational fungicide program to control disease effectively, limit pathogen resistance, and maintain superior turfgrass color and quality in a cost effective manner (http://gri.gg/edu1601). For warm season turf mangers, the summer serves as an opportunity to cultivate and maximize root and shoot growth heading into the fall. Moving forward, superintendents will have to deal with localized dry spot, high heat, general water management issues, and increased disease pressure – including anthracnose on annual bluegrass and gray leaf spot (Pyricularia grisea) on perennial ryegrass. Some strategies to deal with July and August conditions, particularly in areas with the highest rainfall, include frequent needle tining, Figure 2. Dollar spot on a creeping increased mowing heights and perhaps cutting with tri-plexes and smooth rollers, bentgrass fairway (July 21, 2015) low dose and frequent nutrient inputs including phosphite, routine fungicide applications, and light frequent sand topdressing. Generally, it’s important to fine tune programs for efficiency and control those things that you can control including calibration, correct fertilizer and fungicide rates, and using the correct nozzles. This time of year always represents a difficult time to manage cool season turfgrasses but with careful planning, observation, and quick decision making you’ll get through another summer despite the curve balls mother nature throws at you.
References: 1. McDonald, S. J., Dernoeden, P. H., and Bigelow, C. A. 2006. Dollar spot and gray leaf spot severity as influenced by irrigation, chlorothalonil, paclobutrazol,and a wetting agent. Crop Sci. 46:2675–2684. 2. McDonald*, S. J., Dernoeden, P. H., and Bigelow, C. A. 2006. Dollar spot control In creeping bentgrass as influenced by fungicide spray volume and application timing. Online. Applied Turfgrass Science doi:10.1094/ATS-2006-0531-01-RS. 3. Smiley, R.W., P.H. Dernoeden, and B.B. Clarke. 2005. Dollar spot. In: Compendium of Turfgrass Diseases. 3rd Edition. pp 22-24.
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