Several golf course superintendents have asked about "large wasps", especially in and around bunkers, in the past week. This makes me think that others might be experiencing the same thing. (Note that the insect in question also sometimes forms nests in lawns and other areas where soils are relatively sandy and the turf cover is sparse.)
In almost every case, I suspect the wasps you are seeing are cicada killers. The markings resemble those of a wasp, but they are much larger than the typical New England wasp. Cicada killers are solitary wasps that prey on cicadas. Females dig a burrow, lay eggs, and then seek cicadas to provision the nest. As the cicada killer larvae hatch, they have a lovely dinner of a cicada awaiting them.
While female cicada killer adults have stingers (which they use to insert eggs into the target cicada), they normally do not sting people and normally are not aggressive toward people. Males do not have stingers but are territorial, so when a nervous golfer starts swinging a golf club or swatting with his arm, the male may feel like it is under attack and become more aggressive. It is difficult to convince golfers that these very large wasps are not harmful to people, so many superintendents seek options to control the wasps.
Cicada killers are most common in areas with light soils exposed to sunlight for much of the day and close to areas with trees where the cicadas can be found in abundance. (Golf course bunkers certainly meet that description!!!) Cicada killer burrows can be fairly extensive and, if formed in vegetable gardens, can cause mechanical damage to roots.
According to my turf entomology colleagues, if treatment is deemed necessary, the best option is to apply carbaryl or a pyrethroid directly to the nest entrances, preferably when the wasps are in the nests. That normally would be very early in the morning or late in the evening. Broadcast applications usually are not effective.
But because cicada killers are not turf pests as such, I suggest that you try to work with your golfers or customers and convince them that the wasps are important predators in the ecosystem and to stop swatting at them!!!
For more information and photos, refer to the following fact sheet courtesy of the University of Kentucky:
Submitted by: Dr. Pat Vittum