You Are Here: Management Updates 2004 Archive August 12, 2004

Date: August 12, 2004
Category: Insects
Subject: Cicada Killers, Ants, Chinch Bugs

1. Cicada killers: Over the past two weeks, we have received many reports of "very large wasps" in various turf settings, from home lawns to cemeteries to golf course fairways. In most cases the wasps are probably cicada killers, predatory wasps that kill cicadas and carry them back to their nests to provide food for the young wasps.

According to Dr. Dave Shetlar, my counterpart at Ohio State University, cicada killers usually are not very aggressive against people, but that is scant comfort to a person who encounters several of these wasps during an innocent stroll. Regardless of the textbook reports, the wasps can be rather "territorial" on occasion, and it is very unsettling to be dive-bombed by an inch long wasp. Cicada killers seem to prefer areas where turf is weakened or thin. For example, they often appear in or near bunkers on golf courses, where the underlying soil is more sandy and prone to desiccation. Anything that can be done to maintain a dense turf cover should discourage their activity in future years. Of course, that is more easily said than done!

Cicada killers are not direct pests of turf but because of their size and their occasional penchant to be aggressive around people, some turf managers are pressured by their clients to reduce wasp populations. The only approaches I have seen mentioned involve applications of insecticides in or around the nest entrances. I have not seen efficacy data for insecticides used against cicada killers, but am passing on information gleaned from various publications, primarily out of Ohio State.

Shetlar claims that an application of Sevin™ dust near the nest entrances can be effective. He notes that the application should be made in the evening - so mark the locations of the nests during daylight and return as night is falling. Apply dust around the entrances. The foraging cicada killers will encounter the dust as they return to the nest, and carry some of the dust on into the nest to other inhabitants. (Note that some Sevin™ dust labels, available in home garden supply stores, include turf while others do not.)

In addition Shetlar claims that aerosol sprays of "wasp killers" can be effective as well. In this case the turf manager would direct the spray down the entrance hole, again as late in the day as possible. Note, however, that some turf managers have reported that these applications have not been particularly effective, or have only reduced activity for a few days.

I have not seen any mention of phytotoxicity with any of these treatments, but certainly there is always a risk, especially in the hot weather typical of August. And the above observations should not be construed as a recommendation from the University of Massachusetts - just an effort to pass on information from other sources.

2. Turfgrass ants: We have also received several calls reporting heavy ant activity in many locations. Until recently most ant problems seemed to center on golf courses, especially on sand-based greens. But more recently, we have had several calls from lawn care professionals describing ant activity in lawns.

Turfgrass ants (Lasius neoniger) normally prefer sandier soils, but have often been reported on native soils throughout New England. The mounds they form can dull mower blades and suffocate the underlying grass. Efforts to manage ant-mounding activity have centered on relatively slow acting baits and on pyrethroids that can be applied as a broadcast application and provide short- term relief. Most of the field studies conducted on turfgrass ants have been done at Ohio State (Dr. Shetlar again!) and the University of Kentucky (Dr. Dan Potter).

Normally an application of a pyrethroid just as the new mounds become visible (usually in late April or early May in Massachusetts) will provide four to six weeks of relief. Later in the summer, however, these applications only reduce mounding activity for two or three weeks. Baits (available with several different active ingredients) work more slowly, as they must be picked up by foraging ants and carried into the nest, where they eventually reach the queen. They can be applied throughout the season, but it is important to be sure the bait stays dry for at least 24 hours after application.

At the end of the summer, new queens often emerge by the thousands from heavily mounded areas. Dan Potter is experimenting with treating these areas with a pyrethroid as soon as possible after the "nuptial flight" is observed. The flight itself is quite striking - the newly winged ants climb to the tips of blades of grass and eventually leap into the air and take flight. Potter suspects that these new queens are relatively vulnerable ... at the very least, they will need to lay eggs that develop into workers to help create the new burrows for the new colony. So he is hypothesizing that an application of an insecticide that stays in the thatch (because that is where the queens will be active for a few days) should compromise their survival. This is still an hypothesis, but it certainly does make sense intuitively. So again, this late summer application should not be considered a "recommendation" from UMass, but we will keep you posted as we learn more from Potter's studies.

3. Chinch bugs: Many parts of western New England has been "blessed" with lots of rain throughout the summer. Most lawns are growing very well without any need for irrigation. We have had no reports of chinch bug activity. I suspect chinch bugs are in fact present in their usual places, but the consistent rainfall has masked their presence. I would caution you to keep your guard up. If the weather pattern changes (after Bonney and Charley pass through this weekend!), and the weather turns dry, chinch bug activity will quickly translate into the tell-tale symptoms - patches of yellowing turf that spread quickly in the hot dry conditions. (The inestimable Dr. Shetlar points out that chinch bug populations in parts of Ohio have been lower than normal this year because the moist conditions have enabled some of the natural agents, such as Beauveria bassiana, to thrive.)

- Submitted by: Dr. Pat Vittum