Giant Wasp-As bad as they look?

Home Grown  by Keith Reed
It’s that time of year when the Payne County Extension office gets several calls on two seemingly unrelated issues. Very large wasps and good-sized mounds of loose soil (not quite as big as those caused by a gopher) in the landscape. This is really just one issue, the Cidaca killer wasp as it prepares it’s in-ground nest for the next generation.

Your first encounter with a Cicada killer can be a disconcerting experience. These very large yellow and black wasps (about an inch and a half long) are common in our part of the world. The assumption is that any wasp this big with a stinger must be bad. This is perfectly understandable but in reality this insect is rarely a real problem for anything other than the cicada (locust). The wasp stings and kills the cicada and drags it to its burrow where it becomes the food source for the next generation. The burrows are easily recognized as a hand sized mound of soil around a thumb sized hole. These burrows are often in bare soil areas such as flower beds and vegetable gardens but can also be found in lawns.

Although rare, female Cicada killers can sting people. Please note that they will generally only do so when provoked. The male Cicada killer is more aggressive but does not have the capacity to sting. These insects are normally solitary although it is not uncommon to see several in one area. When it is dry, as it is now in parts of the area, you can expect to see an increase in activity at water sources such as bird baths and animal watering dishes.

As already mentioned, these insects are not usually a problem. However, in situations where control is warranted, there are a couple of options. Any knock-down wasp product will be effective provided you can catch them when they are not moving (not an easy thing to do). The best control option is to treat the individual mounds with a small quantity of insecticidal dust labeled for wasps. As the wasp crawls in and out of the burrow, it will come in contact with the insecticide. Retreatment may be necessary in the case of rain or heavy irrigation. Broadcast applications of general purpose insecticides are not particularly effective for control of this insect.

For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at
keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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