Foreign Invaders

In the 15th century, as European explorers sailed the seas and discovered the "New World," they carried with them the future money-makers of the pest control industry. Dog and cat fleas, Norway and roof rats and American and German cockroaches were some of the pests that made the trip across the oceans and established themselves in North America. Not one of these structural pests has been eradicated from North America and each is still an important structural pest today — hundreds of years after their introduction. These imported pest species and others have allowed many pest control companies to generate millions of dollars in revenues and have provided great careers for tens of thousands of people.

But not all the great pests in the world were brought to the United States by our ancestors. Some have hitched a ride here fairly recently. Consequently, the importation of exotic species continues today, guaranteeing a profitable future for the pest control industry and providing new control challenges on a daily basis. For instance, ants and cockroaches are today’s top household pests and it is amazing how many of the problem pest species are imported. Of the 69 or so species of cockroaches that are found in the United States, at least 24 originated from other countries. More importantly, about 12 of those imported species are common structural pests. In the case of ants, most of the important names for the pest control industry have been introduced from foreign lands, including the red imported fire ant, ghost ant, Pharaoh ant, white-footed ant, Argentine ant and pavement ant. And although cockroaches are still important structural pests, many surveys have revealed that these newly imported ant species have replaced cockroaches as the No. 1 pest in the urban environment.

Why are these alien ants so successful and troublesome to PCOs? Or, for that matter, why do imported species of pests generally tend to be more trouble for PCOs than native pests? While there are numerous reasons for their success, a few of particular interest are noted here.

REASON 1: ABILITY TO EXPLOIT DISTURBED ENVIRONMENTS

The red imported fire ant (RIFA), Solenopsis invicta, was brought into Mobile, Ala., sometime in the 1920s or ’30s. In their native land, Brazil, fire ants outcompeted other ant species by re-invading flooded land faster than other ants. Colonies of RIFAs survive floods by gathering into a ball-shaped mass and floating on the water’s surface until the water level declines. In this way, the red imported fire ant can quickly establish thriving nests in these disturbed flooded areas.

RIFAs hitched a ride to the United States in the ballasts of ships that returned from Brazil or Argentina. Upon reaching the United States, RIFAs spread like wildfire throughout the Southeast stinging everything in their path and causing serious damage to Southern agriculture. For example, in 1948, it was estimated that RIFAs caused $500,000 in damage to crops in Mississippi. As the quality of life in the United States increased, the success of RIFAs also increased due to their ability to exploit disturbed environments.

Urban — as well as rural — environments provide RIFAs with frequently disturbed environments that they are programmed to exploit. As farmers plow their land and builders clear lots to construct homes and shopping centers, they disrupt the land, killing competitors and predators of RIFAs. Colonies of RIFAs in surrounding areas quickly invade, like they do in their native land, and gain a foothold in the area long before their enemies do. The construction of highways and the simple act of mowing one’s lawn is disruptive enough to give RIFAs an advantage over its competitors and predators. Furthermore, the old days of spraying many acres of land in an attempt to eradicate RIFAs often proved more detrimental to their enemies than RIFAs themselves. Obviously, the process of urbanization has guaranteed the success of the red imported fire ant.

Pest control operators profit by recognizing that their customers’ lawns and property are disturbed habitats that need constant service. Some of the most profitable PCOs are those using delayed toxicant baits or IGRs for RIFA control so as not to further disturb the natural environment in the area.

REASON 2: MAINTENANCE AND BEAUTIFICATION OF URBAN ENVIRONMENTS THAT CREATE ENVIRONMENTS SIMILAR TO OR BETTER THAN THAT OF THEIR NATIVE LANDS

The white-footed ant, Technomyrmex albipes, and Asian cockroach, Blattella asahinai, are examples of imported insects that survive better in the United States than in their native lands. The white-footed ant is a very recent introduction into the southern United States that is native to Japan and its surrounding islands. When first collected in Homestead, Fla., in 1986, it was not considered to be a major threat. But within five years structural infestations were being reported and the ant was rapidly spreading up the east coast of Florida. Colonies of white-footed ants range in size from hundreds of thousands to more than one million individuals. Large colony size and unusual biology make the white-footed ant a formidable foe. Unlike typical ant species, white-footed ant colonies contain workers that do not regurgitate food between other members of the colony. Instead, the workers lay unfertilized eggs — trophic eggs — that are fed to non-foraging ants within the colony as well as to ants in the developing stages. This aspect of their biology makes baiting difficult since the foraging workers are not transferring the bait toxicant to other members of the colony.

The Asian cockroach was discovered in Florida in 1985 and has steadily spread northward into Georgia and South Carolina. Populations of more than 250,000 per acre are common about five years after establishment in an area. Because they are similar to German cockroaches in appearance, residents are very disturbed when several hundred cockroaches invade their homes nightly. Their entry into houses and businesses is due to their aggregation on lit surfaces, such as porch lights and exterior security lights on apartment complexes and commercial establishments. At sunrise, they then crawl indoors through cracks around doors and windows.

While their unique biologies make the white-footed ant and Asian cockroach difficult to control, the urban environment here in the United States provides them a habitat more suitable than their native environment. In their native land, white-footed ants live in dry grasslands and forest margins and dominate mangrove woods on the Nansei Islands — hardly an important urban pest. Similarly, the Asian cockroach has been collected from sugar cane stubble to dry grasslands and forest margins in its native land. Both species need to feed on nectar and honeydew produced by sap-sucking insects.

Residents in urban communities and commercial landscapers spend a great deal of time and effort beautifying their landscape. Planting various types of flowers and succulent shrubs is attractive to a wide variety of insects that suck plant juices or collect pollen or nectar. The year-round beauty and function of these plants requires intensive maintenance practices such as irrigation and fertilization. This, in turn, creates a continuous supply of nectar and honeydew for these pests, especially in southern regions where moderate temperatures exist throughout the year. Even the residues within trash cans and dumpsters are adequate to sustain large populations of insects throughout the year.

The white-footed ant and Asian cockroach are prime examples of imported insects that have used the urban environment to become a dominant species — a position neither the white-footed ant nor the Asian cockroach would normally hold in their native land. PCOs who understand these pests’ biology and habitats gain a significant advantage over their competitors.

REASON 3: ABILITY TO OCCUPY A NICHE NOT OCCUPIED BY NATIVE INSECTS

Sometimes imported insect species are able to inhabit or exploit areas that are not normally occupied by native insects. For instance, the success of the Formosan termite, Coptotermes formosanus, which was imported into the continental United States in the 1960s, can be attributed not only to its aggressive nature, but also to its biology.

The Formosan termite is able to construct carton nests in walls of structures that act as "micro-environments" for temperature and moisture regulation. Unlike native subterranean termite species that must typically return to the soil for moisture and contact with the colony, Formosan termites often construct carton nests directly in the structure where there is added protection from predators such as fire ants. These carton nests can contain a large reservoir of moisture, allowing Formosan termites to survive for an extended period of time even though they are cut off from soil contact.

Not only is the Formosan termite heavily protected from invaders, its carton nest within a structure is usually isolated with few, if any competitors, challenging them for resources. Their highly regulated "micro-environment" becomes an incubator for egg and termite development so that, when coupled with a lack of enemies, colonies have the capability of growing to enormous sizes.

Formosan termite colonies can contain up to 5 million individuals — numbers unheard of by native colonies of subterranean termites. The Formosan termite’s closely regulated and secure micro-environment in urban structures provides this imported structural pest with an ecological niche all of its own.

REASON 4: SPECIAL SITUATION: BIOLOGICAL CONTROL GONE BAD

The term "biological control" is commonly used in agriculture and usually involves the release of a pests’ natural enemies to obtain control of a troublesome insect. An example is the multi-colored Asian lady beetle, Harmonia axyridis, which was introduced into the southern United States from Asia by United States Department of Agriculture researchers to control aphids, scales and other agronomic pests. Upon their release, Asian lady beetles spread rapidly throughout the South to the Midwest and beyond.

Although an important rule of biological control is to use natural enemies that do not have the potential to become pests themselves, the Asian lady beetle did not comply with these rules in urban areas.

When host plants and their insect prey die out for the season, large numbers of Asian lady beetles congregate in walls, attics, porches and any other locations in structures that provides shelter and warmth for them to overwinter. Homeowners frantically called PCOs when Asian lady beetles covered and invaded their homes. Homeowners feared that these beetles would eat their homes, furniture and belongings or, perhaps, infest their pets. However, these beetles do not cause structural damage or physical harm to humans or pets, but their mere presence in such large numbers is a tremendous nuisance that causes a great deal of stress to many homeowners.

CONCLUSION

From the situations mentioned in this article, it should be evident the importance of imported species of insects. And while the majority of imported insects never establish or become economically important here in the United States, those that do are some of the most difficult pests to control because of their ability to exploit the numerous resources provided by the urban environment.

With the understanding that the urban environment provides optimal conditions for exotic species of pests, many PCOs can greatly profit from service calls about these pests. But those not keeping up to date with the constant influx of imported pests will have higher callback rates, lower profitability and continued headaches.