Dr. Pete's Turf Tips
Peter H. Dernoeden, Ph. D.
There were about 20 days of overcast, cool and rainy weather in May. The persistent wet and overcast weather made it nearly impossible to keep up with mowing. Some greens became puffy and were scalped. Sunny days arrived in early June, but the weekend of June 11 and 12 brought a blast of summer weather that shocked turf. On the aforementioned weekend, temperatures reached 90ºF, winds were constant and in excess of 25 mph, and relative humidity was less than 45%. The rapid drying led to damage from drought stress or from mowing wilting turf. It also brought on localized dry spots.
May weather promoted excessive growth and everyone mowed feverishly. Players could not find balls in roughs and everyone was complaining. The surface organic layer (i.e., thatch plus mat) in some greens became puffy as the wet conditions made thatch and stems swell. Puffy organic layers cause mowers to sink and scalp, injuring both leaves and stems. Recovery can be slow from this type of damage. Attacking thatch layers is a constant battle on greens. Coring with wide diameter tines spring and autumn in combination with heavy topdressing is very important, but organic layer management measures are needed throughout the growing season. A good, yet largely forgotten tool is the spiker. Greens can be rapidly spiked with minimal damage. The knives of the spiker cut into organic layers to allow for ingress and egress of gases and water; mixes sand into the organic layer; disrupts algal scums; and cuts stems to promote density. Periodical coring with small diameter solid tines and light topdressing greens are most helpful during the golfing season. I recognize that many courses have limited staffs and tight budgets, but try to accomplish some form of periodical surface aeration in the summer. Grooved rollers are preferred during cool and wet weather, but now that summer heat is upon us it is best to switch to less potentially injurious solid rollers.
A combination of bright sun, high temperatures, gusting winds and low humidity, dried soils rapidly on
June 11 and 12. Drought stress, damage associated with mowing wilting turf and localized dry spots became troublesome. During daytime hours in summer, the best way to deal with stress on greens, collars and approaches is via syringing. Syringing cools leaves and allows for the natural movement of water from soil to roots (assuming available water present) and through opens pores (i.e. stomates) on both lower and upper leaf surfaces. This effect is called transpirational cooling, which is powerful in alleviating heat stress. Syringing by hand is ideal, but many clubs just don’t have enough staff and thus will need to use the overhead system. Regardless of using a hose or irrigation heads, someone needs to be scouting vulnerable greens from about 10AM to 4PM on bright summer days. When syringing by hand, it should take no more than 5 minutes to syringe the average size green. The objective is to deliver a light coating of water without getting too much water into the thatch-mat layer. A few turns of irrigation heads are an alternative. When using heads, it is important not to deliver so much water that thatch-mat layers become saturated on hot and sunny day. Water saturated organic layers can actually promote excessive heat stress in stems and roots. It is most important to avoid puddles, which can kill turf (i.e., scald) within an hour or two on a hot sunny day in low cut grass. Soil moisture must be replenished throughout the rootzone at night. Deep watering after sunset gives turf all night to rehydrate (i.e., become turgid), recover normal function and for water to drain properly before early light when it is time to mow. Pre-dawn watering is preferred if greens are not protected by fungicides.
Localized dry spots (LDS) are common on golf courses during summer and mostly are restricted to sand-based rootzones, or where sand topdressing has been used over native soils. Water repellency is caused by microbial decomposition of organic matter, which releases hydrophobic substances that coat individual sand particles rendering them hydrophobic. The water repellant zone typically is restricted to the upper few inches of soil. Curative LDS management involves breaking through the water repellent zone using a combination of coring and flushing-in a soil wetting agent. Preventive applications work best and do not require special application procedures. To be most effective, preventive wetting agent applications should be initiated several weeks prior to the anticipated onset of hot weather. Fungicides have no known effect on LDS.
