When summer did arrive it arrived with a bang. In 2009 the Chicago area posted only 6 days where the high temperature broke the 90 degree mark. In 2010 that number was quadrupled with 26 days breaking the 90 degree mark. This is consistent with Chicago’s trend of really hot summers occurring about once every 12 – 14 years. The summers of 1983, 1995 and 2010 are etched in the minds of local superintendents as difficult years to keep turf alive. To compound things, in 2010 the heat was combined with excessive rain that caused flooding and water logged soils. Hot, humid, and wet is a deadly combination for cool season turf grasses. Root zone oxygen is displaced as soil pore space fills with water. Water logged soils retain heat at a rate 10 times greater than that of oxygenated soils. Saturated soils that heat up during the day retain heat overnight, never cooling down. When air temperatures climb above 85 degrees the plants ability to undergo photosynthesis begins to diminish. As a result the plant rapidly uses up all of its stored carbohydrate reserves, (reserves that were deficient to start with due to the prolonged winter) and is left to starve to death as its shallow root system boils in a primordial stew.
In this weakened condition the plant is easy prey for opportunistic fungal diseases. While fungi are always present, they are normally held in check by environmental conditions and the plants natural ability to fend them off. Physiological decline of the grass plant leaves it vulnerable to a myriad of plant pathogens including: brown patch, waitea patch, summer patch, take-all patch, localized dry spot, fairy ring, dollar spot, anthracnose and pythium blight. The relationship between the plant, the environment, and the fungi is typically referred to as the “Disease Triangle”. In 2010 there is no doubt that the “Disease Triangle” was out of balance and the fungi had the upper hand. Dr. Derek Settle is the plant pathologist employed by the CDGA; he is stationed at the Midwest Golf House. As part of his service Derek makes site visits to local Chicago courses to help diagnose turfgrass related problems. In 2009 Derek did site visits at 50 local courses. In 2010 Derek received calls for site visits from 136 courses (we had Derek out a couple of times last year); this is the most calls that Derek has received dating back to 2006 when he was hired by the CDGA.
Granted, not all courses experienced turf loss, so this begs the question – why? Typically the answer has to do with course micro climates. You need not compare one course to another to find microclimates; you can identify microclimates within NCC. The left edge of #5 fairway was hard hit by an outbreak of pythium, yet the 18th fairway was undamaged – why? The truth is that there is a micro climate that exists on the left side of #5 fairway. It is a low area that sits wet longer following rain events. The dew burns off slower on the left side of #5 contributing to leaf wetness and disease pressure. In the winter time the tree line along the fence on #5 shades the left half of the fairway causing prolonged snow and ice cover, this means the turf on that side of the fairway is weaker coming out of winter. The combination of the tree line on the left and the hillside on the right reduce air flow over the fairway. Stagnant humid air reduces the ability of the grass plant to undergo evapotranspiration (ET). This is the plants cooling mechanism; it is very similar to how we cool ourselves through the process of perspiration. Think about what happens if you sit in a hot humid steam room for too long. Once you have had all you can take you leave the sauna and find relief in the cool air outside the sauna. The turf does not have the ability “leave the sauna” and seek out the air conditioning and a cool beverage. It has to survive long enough for relief to come in the form of a drop in night time temperatures. As the air and soil temperatures cool down the plant finds relief. If the temperature doesn’t drop, or is the soils are saturated with water and are retaining heat, then the relief does not come. A surprise thunderstorm on a 90 degree summer night can be a superintendent’s worst nightmare.
So how do we build on this for 2011. Sound agronomic practices are the key to surviving periods of stress. Aerification, thatch management, proper fertility, proper irrigation, good drainage, proper air exchange within the root zone, good air movement over the turf, proper exposure to sun, good mowing techniques, proper stress management, adequate topdressing, the use of proper grass varieties, and plant protectant programs are all part of developing a successful turfgrass management program. Each winter we evaluate and refine our program.Related posts from last year:
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