Ant of the Future:Rasberry Crazy Ant

Invasive species represent a major threat to the world’s biodiversity, agriculture and economy, and also can provide unknown impacts on native ecosystems. An invasive species is an introduced species from different parts of the world that arrives without its natural predators and pathogens. This lack of natural control often gives these species an advantage over native species, and therefore can become major pests. A particularly troublesome ant recently has invaded Texas and caused concerns over available control measures.

In 2003, the Center for Urban and Structural Entomology was notified by Tom Rasberry, ACE, owner of Budget Pest Control, of a pest ant found in an industrial area of Pasadena, Texas. Rasberry crazy ants (RCAs) were found in overwhelming numbers. At this time it was chiefly a nuisance pest; however, it had caused considerable financial damage, including electrical shortages in equipment ranging from phone lines to traffic signals. Amazing densities of RCAs have been found in infested areas, and field observations indicate a displacement of the Red Imported Fire Ant (RIFA), Solenopsis invicta Buren.

Since its introduction prior to 2003, RCAs have spread to numerous locations surrounding the greater Houston, Texas, area. This species has been confirmed in 11 counties in southeast Texas, including two that border Louisiana (Jefferson and Orange). Field investigations indicate that the spread of RCAs into rural areas is likely to occur at higher rates than observed in urban areas. The quick expansion of its range in southeast Texas has resulted from the movement or transport of potted plants, soil, sod, garbage, railcars, and the ants hitchhiking on vehicles.

Once these ants have been introduced, they spread rapidly throughout the area. Its propensity for foraging and nesting at both ground and above-ground levels is quite troublesome. Field observations show adverse effects on both ground and tree-nesting animals. Of particular concern are some state-protected birds. It is highly probable that these ants will have a dramatic effect on the ecology of the southeastern region of the U.S.

Confirmed reports indicate RCAs have caused electrical shortages in a variety of apparatuses in buildings, including phone lines, air conditioning units, chemical-pipe valve computers, control panels in chemical plants, traffic signals, car computers and sewage lift stations. Additional residential complaints include reports of bites; however, they do not sting like RIFAs. There are also reports of abnormal behavior of companion animals in the presence of high levels of RCA infestations. Populations of this ant are difficult to control and eradication is highly improbable.

The Texas Department of Agriculture and the U.S. EPA announced a FIFRA Section 18 Crisis Exemption for the use of Termidor SC termiticide/insecticide for control of RCAs, Paratrechina sp. nr. pubens, in Texas. This species is termed “sp. nr.” because current research suggests that it is a species near, and likely differentiated, from the occasionally pestiferous P. pubens. In addition, the U.S. Department of Agriculture and the Texas Department of Agriculture formed a task force to evaluate needed responses to this invasive ant. To date there are no current state or federal expansion/prevention measures in place.

Identification. RCAs are similar to some ants that may create high densities that can confuse pest management professionals. RCAs have only one petiole (a.k.a node), an acidopore (circle of hairs at tip of abdomen), standing macrochetae (large, erect hairs), and relatively long femurs and scapes. They are reddish-brown, about 2.5 mm (1⁄8 in) in length, and exhibit erratic foraging behaviors that are associated with very high densities. This species has been confused with odorous house ants (OHAs), Tapinoma sessile; Argentine ants, Linepithema humile; and black crazy ants, Paratrechina longicornis. Unlike RCAs, OHAs do not have standing macrochetae and OHAs smell like rotten coconuts when crushed. Unlike RCAs, Argentine ants are thinner, typically darker in color, the head is more heart shaped, and they do not have as many standing macrochetae. Black crazy ants are much darker in color and have a longer thorax, femurs and scapes than RCAs. All three of these other species can exhibit high densities, which may cause PCOs to provide a misidentification, leading to improper treatments.

Control. Research data suggest that baits may be used in the overall management strategy and they may provide additional population suppression when used in combination with perimeter treatments. Baiting in early spring offers the best results. The current bait labels will need to be adjusted for greater product placement to create effective control of RCAs. Unfortunately, our research has indicated that application rates listed on the current product labels will have difficulty in providing adequate control of RCAs.

Exterior treatments are the key component pest management professionals need to use for suppression of RCAs associated with structures. PCOs need to be aware that RCAs will nest under any debris on the property. It is critical that treatments be applied under as many articles on the ground as possible. When treating the structure and yard debris, PCOs will essentially create a buffer zone. If infested structures are on adjacent properties near your account’s property line, suppression becomes more difficult. Adjoining properties can have a profound effect on any treatment efforts. If sites are poorly maintained or heavily wooded, you will have to provide treatments on a more consistent schedule. Heavily infested accounts will often need three to eight treatments per year, depending upon specific environments and proximity to the property line.

Research at TAMU has indicated a clear improvement and consistent control of RCAs when using the method prescribed in the Termidor SC crisis exemption label. The Termidor SC crisis exemption label is only to be used in Texas counties listed on the Termidor SC crisis exemption label. TAMU entomologists have positively identified RCAs in these counties (see www.tda.state.tx.us). For exterior perimeter treatments around structures apply a 0.06 percent dilution of Termidor SC to surfaces up to but not to exceed 3 feet up and 10 feet of sod out from the foundation. The product may also be applied up to 10 feet around utility wires (electrical, telephone or cable) and as a foam treatment where ants may enter, trail or nest. Broadcast treatments may be applied two times per year per structure.Both container label and the crisis exemption label must be in the possession of the user at the time of application.

After treatment, cadavers will number in such great quantity that removal of the piles is necessary for the remaining individuals to reach the treated surfaces. This will help to facilitate the product’s horizontal transfer. For indoor infestations, TAMU suggests the additional use of a non-repellent, residual insecticide indoors.

A precedent has been set in Texas for a crisis exemption for the RCA. If this ant is or becomes a problem in your state, the opportunity may exist for your state regulatory agency to request a similar label. It is imperative that pest management professionals use the crisis exemption responsibly. Due to the public nature of this exotic ant, pressure will remain on the TDA and EPA to enforce the crisis label. If this exemption is revoked due to careless usage, PCOs will have lost an integral tool for population management of this ant.

Authors’ note: If you suspect that you have RCAs, send a sample to your local extension entomologist, or the Center for Urban and Structural Entomology, 2143 TAMU, College Station, TX 77843.

Dr. Jason Meyers is a market development specialist, BASF Pest Control Solutions, Kansas City, Mo. Dr. Roger Gold is a professor and endowed chair at the Center for Urban and Industrial Entomology, Texas A&M University. Tom Rasberry, ACE, is owner/operator, Budget Pest Control, Pearland, Texas.