Heat Stress

Summer has arrived in full force now in southern Michigan and 80/90 degree days are going to become more common.  With this heat comes turf that displays poor color, vigor and growth (along with a large amount of stress for superintendents).  Combined with these high temperatures, the Northville area has seen precious little precipitation over the past couple weeks.  This is painfully obvious in non-irrigated portions of the golf course (i.e. the rough).  Both of these factors will be the crews main combatants for the rest of the summer. 

                                                Non-irrigated vs. Irrigated

Why does heat have such a negative effect on plant health? There are several reasons, some similar to the effect of heat on humans, while others are specific to plants.  Here are a few of the major ones. 

• High temperatures inhibit enzyme function, which are the catalysts of the important metabolic pathways within plants, such as photosynthesis and aerobic respiration.
• Along with heat comes the release of free radicals (toxins in the plant).  Plants have natural defenses towards these but in periods of high temps and low moisture the plant cannot produce the anti-oxidants necessary to combat the free radicals. 
• Heat can make plant membranes too fluid (not structurally sound).  The turf cannot recover from traffic as well and gives long cut grass a drooping appearance. 

The turf at MCC is of the cool-season variety, which prefers temperatures within the 65-80 degree range.  During periods of high temperatures the turf depends heavily on an extensive root system it grows during the spring. Poa annua (the grass on our tee's, greens and fairways) is a plant that can survive on extremely shallow roots.  However it gets into trouble during times of low moisture and heat because it doesn't have the root length and mass necessary to uptake enough water.  We help it out by frequent, light watering.  Heavy irrigation would keep a large amount of water in the soil but open the door for fungal pathogens that thrive in high heat and moist conditions.        

Dark purpling is a sign of heat stress

The summer of 2010 was one of the hottest on record and while we have not reached those extremes this year, the crew will be babysitting the turf for the next couple months.  Until we have past this tenuous period enjoy the summer weather and quick greens.