Turf Magazine - June, 2014

SOUTH FEATURES

Tawny Crazy Ant a Growing Concern

They're not really crazy, they're just hungry and they cluster in huge numbers
By Mike Ingles


Mature Nylanderia fulva tending their young.
Photo courtesy of Joe MacGown, Mississippi State University.

In Texas, there's a new sheriff in town. He's not very big but he's plenty tough.

The tawny crazy ant (TCA), aka, Rasberry crazy ants, are voracious eating machines and, as their name implies, they swarm over territories in dense numbers with quick erratic movements making it seem as though they are acting crazy. They're not crazy - they're just busy displacing the red imported fire ant as the region's number one ant problem.

The TCA is yet another invasive species from South America. It feeds on both plant seed and animal substances. Tom Rasberry, owner of Rasberry's Pest Professionals, Pearland, Texas, is credited with the rediscovery of this species in Texas about 12 years ago.

Scientists initially had some confusion establishing the taxonomy of the genus, but it is now recognized as Nylanderia fulva, which had previously been reported in the southern part of the state in the 1930s but subsequently disappeared from the region.



As is evident in this map, Nylanderia fulva are spreading, slowly but surely.
Map courtesty of Joe MacGown entomology Miss State Univ.

"What makes these ants so different is just the sheer number of them, and unlike the fire ants that build mounds and inflict nasty stings, the TCA pretty much leaves humans alone. But tawny crazy ants can overwhelm a household and get into garages, out-buildings, walls, electrical boxes and air-conditioning units doing considerable damage. Although TCA doesn't sting like the fire ant, people battling this menace would rather have the fire ants back," says Paul Nester, Ph.D., extension program specialist - IPM, Texas A&M AgriLife Extension Service in Houston.

TCAs have a never-before-seen ability to withstand the sting of fire ants by covering themselves with formic acid, secreted from a gland on their abdomen. This ability, along with the sheer raw numbers of them, are forcing fire ants out of their invaded habitat. TCAs are known to raid mounds of other ant species, and some bee colonies, targeting the brood and consuming their larva, pupa and nymphs. They favor warm moist climates and settle into damp, dark areas such as under loose bark, inside of rotted wood or under stones and brick, and are often found in highly mulched beds, grassy and brushy areas.

How to Identify the TCA

  • Adult colony members, including queens, males and workers, are reddish-brown (although lightness or darkness of their body color may vary).
  • Size: Worker ants are all similar in size (they are monomorphic), with a body length of 1/8 inch.
  • Worker ants have long legs and antennae, although not as long as the crazy ant, Paratrechina longicornis, and their bodies have numerous long, coarse hairs. The antenna have 12 segments with no club.
  • There is a small circle of hairs (acidopore) present at tip of the abdomen (as opposed to the typical stinger found in many ants), a characteristic of formicine ants (found within the Formicinae subfamily).

Sweet tooth

Joe MacGown, research technician, Mississippi Entomological Museum, University of Mississippi State, explains that TCAs are omnivorous, but at certain times they appear to prefer sweet, sugary foods, such as the nectar produced by certain plants wherein species of hemipterans (aphids, plant hoppers, scale insects, whiteflies, mealy bugs, etc.) reside.

"They protect the hemiptera resulting in massive spikes in hemiptera populations," says MacGown. "And the large numbers of plant-sucking hemipterans can be devastating to plants. TCAs simply out-compete many native species, even the invasive ones, reducing biodiversity by preying on insects and small vertebrates, both on the ground and in trees."

According to Nester, large colonies of TCA infested a pecan tree orchard in Manvel, Texas, recently, affecting electrical outlets and water pumps.

"Typical of the species," says Nester, "worker ants commonly protect hemipterous insects on plants and others that excrete a sugary (carbohydrate) liquid called honeydew on which the TCA feed. The presence of the hemipterans can then cause damage to the plants where they remain feeding."

MacGown explains that unlike most ant species, TCAs have many queens per colony, so they can produce an amazing colony size even though the worker ants mostly die off or are dormant in winter. The queens survive. The larger the brood the more voracious its appetite, and colonies sometimes join legions to form "supercolonies" in which staggering amounts of TCAs move through areas in a swarm.

MacGown warns, "It's a serious situation. Infestations to homeowners in some residential areas of Mississippi who have unsuccessfully battled the TCAs have caused people to vacate their homes."

He adds, "Based on their negative impacts in other non-native regions we should be concerned for both plants and animals. For example, in Columbia, Mississippi, N. fulva (TCA) has been reported to displace native fauna, to cause chickens to die of asphyxia, to attack the nasal fossae, eyes and hooves of cattle, and to cause grasslands to dry out as a result of elevated hemipteran levels on plants."



Photo courtesy of Tom Rasberry.

How to Identify the TCA

  • Adult colony members, including queens, males and workers, are reddish-brown
  • (although lightness or darkness of their body color may vary).
  • Size: Worker ants are all similar in size (they are monomorphic), with a body length of 1/8 inch.
  • Worker ants have long legs and antennae, although not as long as the crazy ant, Paratrechina longicornis, and their bodies have numerous long, coarse hairs.
  • The antenna have 12 segments with no club.
  • There is a small circle of hairs (acidopore) present at tip of the abdomen (as opposed to the typical stinger found in many ants), a characteristic of formicine ants (found within the Formicinae subfamily).

For reasons scientists don't yet understand, the ants seem to prefer to cluster inside electronic machinery, such as outdoor electrical boxes, water pumps and air-conditioning units, and have done considerable damage by shorting out units, even starting small fires.

TCA have spread throughout Texas to southern Louisiana, Mississippi, Georgia and Florida. Upcoming studies in Texas, such as one in the Walden community in Montgomery, Texas, in which Nester will soon be engaged, will test the effects of available pesticides applied to multiple homes. Adjacent properties of the approximate same size, will be treated with similar products to measure if the treatment of the area will reduce the population of the TCA over time as opposed to only treating single properties.

"Pesticides are simply one tool," says Nester. "To control this pest we'll have to utilize IPM strategies, including cultural control methods beginning with the removal of harborage such as fallen limbs, rocks, leaf litter and just about anything sitting on the ground that isn't absolutely necessary."

Nester adds that altering the moisture conditions in a landscape is an important tool, so reducing the amount of irrigation, repairing leaks and improving drainage is critical. And being careful not to transport the ant out of infested regions, because they are often found nesting in potted plants, inside garbage bags and beds of pickup trucks, or even in luggage.

Monitor and manage

For green industry pros, Nester advises that honeydew-producing hemipterans should be monitored and managed. Often, products containing the active ingredient imidaloprid or other systemic neonicotinoid are a good option for hemipterans. The drenching of container plants with a synthetic pyrethroid insecticide will also aid in removing the TCA before the containers are transported.

Establishing temporary "buffer zones" using contact insecticides applied to surfaces, such as those containing acephate, pyrethroid insecticides (bifenthrin, cypermethrin, cyfluthrin, deltamethrin, lambda-cyhalothin, permethrin, s-fenvalerate and others) or fipronil can be effective tools. However treatments must be continued after only one to three months and should only be used in conjunction with proven IPM strategies, he cautions.



For some reason, crazy ants are attracted to electrical outlets.
Photo courtesy of Joe MacGown entomology Miss State Univ.

University entomologists, including Nester, will meet this spring in Palm Springs, California, during the annual Red Imported Fire Ant Conference where various invasive ant species, including the TCA, will be discussed.

The author is an experienced business writer who loves writing about issues important to green industry professionals. Email him at duckrun22@gmail.com to reach him or to comment on the article.