|No tools have yet been identified to control the large populations of Rasberry ants that PMPs must face. Photo by Tom Rasberry.|
Call ’em crazy, but the ants named after PCO and entomologist Tom Rasberry seem to have crafted a fairly ingenious plan for infesting our homes and businesses. Namely, where PMPs place treatments, the ants simply pile on top of fellow ant cadavers to create a bridge into the structure of their choice. Crazy like a fox, huh?
Individually, Rasberry ants are manageable. Unfortunately, PMPs must face them en masse, and frankly, the tools have yet to be identified that can control their large populations, which can number in the hundreds of millions. In a matter of just a few years, these pests have spread into 21 counties in Texas, along with many areas of Florida, Louisiana and Mississippi, impacting homes and businesses alike. They are negatively impacting fruit and hay production, having a devastating effect on honeybee colonies, protecting aphids from their natural predators and parasites through tending, and serving as a nuisance to homeowners and their pets. Additionally, these pests are changing the ecological balance by eating beneficial insects.
The Rasberry crazy ant is an invasive species that came to the United States most likely from the Caribbean, explained Dr. Roger Gold, professor and endowed chair in urban and structural entomology at Texas A&M University. “As an introduced species, this ant arrived without any predators, parasites or pathogens. There is nothing to dissuade its advancement in taking over these environments. It probably has been introduced here once or twice before, but only in recent years has it gained a foothold. It is doing possibly irreversible damage, taking out parts of the environmental systems — beneficial insect species, for example — and it is not evident how the ecological web will recover.”
With notable invasions at NASA’s Johnson Space Center in Houston, and some other large corporations where the ants have shut down electrical systems and computer networks due to their penchant for foraging into electronics and circuitry, the Rasberry crazy ant phenomenon has recently caught the attention of U.S. Homeland Security. What if these creatures were to attack the United States’ security systems? Gold said he hopes this awareness will lead to federal support in the quest for management programs, which researchers at Texas A&M, as well as other universities, are working toward.
By Any Other Name. The name “Rasberry crazy ant” was introduced to the industry in 2002, when PMP Tom Rasberry and other entomologists noticed an invasion of these small (about 1/8 inch long), reddish-brown ants in an industrial park near the Port of Houston. The color was unique, and the creature varied from other species behaviorally in that it was resistant to control methods due to its unusually high population numbers. (The female has tremendous reproductive capabilities.)
Calling it “Rasberry ant” made sense. The addition of the “crazy” descriptor was a reflection of its random foraging patterns and the rapid, erratic way it crawls. More recently, the name “hairy crazy ant” has gained popularity, bringing to the spotlight the microsetae hairs on the body that make the ant just a bit furrier than its closest cousins.
In scientific circles, it’s known as Nylanderia sp. nr. pubens, although taxonomists continue to debate the name. “We don’t know exactly what species this is yet,” Gold said. “In fact, proper identification is one of the issues standing in the way of building effective management programs, because the correct scientific and common name would have to be provided on product labels. Because this species doesn’t have an accepted scientific name, the state and federal governments have been hesitant to provide the level of funding thorough research requires.
“The residents of Deer Park, Texas, and other invaded cities and towns don’t need for it to have a name; they have their own names for this pest,” he added. “They just need some relief. They’re vacuuming up a gallon or two of these each day from their homes, and that’s following treatment.”
What else do we know about Rasberry ants? They bite but don’t sting. And they’re omnivorous. They’ll eat other insects for protein, but they favor sugars. As aphid-tenders, they protect these fruit tree pests from parasites and predators in exchange for their honeydew. They also live extremely well with human beings, thriving on crumbs from our pantries and other waste.
Management: Still a Question. Although the industry hasn’t identified a foolproof management program for the Rasberry crazy ant yet, Gold and his team, as well as other research teams, continue to investigate alternatives.
“Integrated management — a combination of biological control, chemical treatment and common sense — is our hope,” Gold explained. “Remember, going into these accounts, that it’s not difficult to kill the ants; rather, it’s difficult to kill enough of them to provide homeowners relief. It’s not a one-time approach: At the rate these creatures reproduce, you can be right back where you started from within just a few weeks. You’ll be making repeated trips to these accounts. You need to charge for these services, and don’t overpromise on what you can deliver, given the resources at hand.”
Sanitation and Restricting Resources: IPM begins with sanitation efforts. That’s especially true for pests like the Rasberry crazy ant, for which the populations are so large that you can have mountains of cadavers. You also have the living relatives eating their dead comrades, so sweeping them up actually removes one of their food sources. The debris around a home needs to be picked up and simplified as well, since these pests will nest under anything moist that’s left on the ground.
Very little work has been done to investigate methods (beyond sanitation) for restricting the ants’ access to resources. Creating physical barriers to screen them out is difficult since they are so tiny, but a key to their management is sanitation.
Pesticides: Pesticides have emerged as our best defense for this pest, said Gold, at least for the time being. Although sanitation measures help, they don’t resolve the issue. So a variety of readily available pesticides are being tested to determine which are most effective. Here are the results shared by Gold and his research team:
- Granular baits: Because granular and liquid baits have been so effective with fire ants, it was natural to believe they might be effective with Rasberry crazy ants. They have tested effective in suppressing, but not eliminating, populations. Gold noted that some carpenter ant bait “shows promise.” The ants are attracted to the bait granules and appear to feed on the chemical matrix.
- Liquid baits: Like granular baits, liquid baits containing imidacloprid significantly reduce the number of ants, but for only a short period of time.
- Gel baits: Many commercially available gel baits are attractive to these ants, but they eat them so rapidly that it’s impractical (relative to the benefit received) to keep resetting them. Gel also can be messy, and accumulated dust and debris can render it unacceptable to the ants over time.
- Sprays: Spray pesticides work well in terms of killing ants but don’t necessarily reduce the populations over time. Fipronil is one of the products that does offer some longer-term effects against this ant species, but it can be used only twice a year, per label directions.
- Combination treatments: Work is still being done on evaluating the effectiveness of combining various outdoor and indoor insecticides. The concept behind this treatment approach is to establish a chemical barrier around the structure while also applying a product labeled for the inside of the structure. At best, these combination treatments can reduce the numbers, for a limited period of time. Gold reported that the best-case scenario in his trials involved applying a chlorfenapyr product indoors and fipronil outdoors at the expanded label rate of 3 feet up and 10 feet out. This combination treatment held the experimental population at bay for about 12 weeks.
- Soluble aphid pesticides: Where Rasberry ants are attacking trees, application of an aphid pesticide helps because, although it may not kill the ants themselves, it does kill the aphids, thus removing the honeydew food source that has supported the ant population.
The author is a Cleveland-based freelancer. She can be reached at firstname.lastname@example.org.
For more information about Rasberry crazy ants and the research being done at Texas A&M, go to urbanentomology.tamu.edu and choose Rasberry Crazy Ant.