Pest Challenges In the Sunshine State

Convention Extra - Florida Pest Issues

While Florida may be a tourist destination, it’s also a pest haven.

©TeddyandMia | iStock
Figure 1. Tropical sod webworm, Herpetogramma phaeopteralis.

Florida often comes to mind when one thinks about a vacation destination. Whether you’re taking the kids to that “magical kingdom” or it’s off to one of the many beaches on its 1,350 miles of coastline, Florida is, and probably forever will be, America’s vacation hot spot. It also is very well known for its abundance of bugs, but that’s not really advertised much as you’re heading down the Turnpike reading the endless line of billboards.

Florida is truly unique from the rest of the continental United States in that it is the only state that has both sub-tropical and tropical regions. Tropical regions are often said to have only two seasons: wet and dry. However, most of the state’s climate is fairly temperate because no location is all that far from a large body of water. Although it happens from time to time, temperatures rarely exceed 100°F; freezing temperatures do occur in the northern and middle portions of the state, but for only a few days, at most.

High humidity also is a constant, and with the air continually filled with moisture, conditions are usually optimal for feeding, breeding and population growth among Florida critters. This climate doesn’t do much to naturally slow down bug populations. Without that fluffy white stuff falling from the skies and the frigid cold that comes with it, pest management professionals typically are in full swing year round.

Figure 2. Flat-backed cyanide millipede, Asiomorpha coarctata.

Another feature of Florida weather that puts a serious damper on pest control service is daily precipitation during summer months. Sea breezes from the Gulf and the Atlantic build up and collide somewhere in the middle of the state, usually in the afternoon, making the chances for thunderstorms likely. This plays havoc with a tight service schedule; worse yet, heavy downpours can diminish the benefit of recent applications. Applications in progress must be postponed at the onset of rain to abide by pesticide labels.

It’s a tough state not only because of the seven straight months of stifling heat, predictable rain and constant humidity, but because the challenges of tackling a wide variety of pests can at times be overwhelming. Peridomestic bugs thrive in Florida and make their way inside. Earwigs (order Dermaptera), many species of ants, and the American cockroach, Periplaneta americana, to name just a few, find their way inside structures with relative ease. What seems like an impenetrable fortress to many homeowners is really just a temporary obstacle to the constant exploratory and foraging behavior of Florida arthropods.

Figure 3. Yellow-banded millipede, Anadenobolus monilicornis.

To better serve customers, the trend of the Florida operator has moved strongly to exclusion techniques (“An ounce of prevention is worth a pound of cure” to quote Ben Franklin). In many technicians’ tool kits one is likely to find a tube of caulk to seal a crack, a pair of snippers for unruly plants that provide a bridge, or the simple tried- and-true metal mesh to help plug up, block, or eliminate entry points that these multi-legged invaders find and exploit. Smart techs employ a proven strategy of baits or residual dusts to cracks, crevices, or voids and entryways, looking to minimize their impact, yet having the most positive results.

Training, support and cooperation seem to be on the rise. The Florida Department of Agriculture and Consumer Services (FDACS) — which is in charge of enforcement in Florida — has NEVER missed an opportunity to send an inspector to a training (CEU-issuing) opportunity whenever invited, and the University of Florida all but bends over backwards to teach and share. This relationship, and other factors, give the Florida professional applicator every opportunity to provide the most professional and effective service possible.

LAWN & ORNAMENTAL PESTS. As previously mentioned, Florida is no stranger to rainfall. In fact, this state receives more than 50 inches annually. Not only does this rain create indoor pest issues, it opens up a whole new world for lawn and ornamental pests, as well. One such pest is the tropical sod webworm (Herpetogramma phaeopteralis, Fig. 1). This tiny caterpillar can wreak havoc on Florida lawns seemingly overnight, once it has reached the fifth and sixth instar. Their feeding causes the turf to turn brownish in color and often gives the infested area a scalped appearance. They are primarily night feeders, inactive during the day hiding below the thatch.

Another often-encountered creature, when conditions are favorable, are millipedes. There are two species of flat-backed millipedes (order Polydesmida) that migrate in extremely high numbers: These are the greenhouse millipede (Oxidus gracilis) and the cyanide millipede (Asiomorpha coarctata, Fig. 2). It’s interesting to read in Walter Ebeling’s Urban Entomology that some migrations were very large. In one case, it became necessary to apply sand on slippery railroad tracks for traction of locomotive drive wheels due to the squished millipedes. In 1919, a millipede migration caused cattle to stop grazing because of the high numbers on the pastures. Large quantities of drowned millipedes were found in wells, rendering the water unsuitable for drinking for a time. Field workers became sick while hoeing a cornfield because the millipede population was so high the odor from the crushed millipedes overwhelmed them. Ebeling goes on describing several other occurrences in his publication. In Florida, these inch-long troublemakers are often found crawling over lawns, sidewalks and even get into buildings by the thousands.

Figure 4. Colonial tent-web spider, Cyrtophora citricola.
Left: Daniel D. Dye II, Right: Gerald Wegner

One invasive species, the yellow-banded millipede (Anadenobolus monilicornis, Fig. 3), is known to exist in numbers high enough to cause South Florida homeowners grief. Although, this millipede is an introduced species, its population has grown quite large in recent years. They crawl over lawns, patios, sidewalks, houses and other structures. Monkeys in a Miami zoo have been seen rubbing these millipedes on their fur to help repel mosquitoes and other insects. The monkeys also use them to get a little high. Researchers are still not sure as to how far north these may spread into Florida.

SPIDERS. Florida is home to four species of widow spiders (Latrodectus spp.) — the infamous southern black widow (L. mactans), the regionally common brown widow (L.geometricus), the sporadically-encountered northern widow (L. variolus), and the rarely-encountered red widow (L. bishopi). Despite the relative abundance of widow spiders in Florida, verified human encounters resulting in bites with serious consequences are uncommon. An accelerated northerly and westerly expansion in the distribution of the brown widow into nearby states has been attributed to the winds associated with recent hurricanes (e.g., Katrina) that passed over Florida from the southeast, apparently carrying certain fauna with them.

Gerald Wegner
Figure 5. Black pyramid ant, Dorymyrmex medeis.

One spider getting more attention in Florida is the non-native colonial tentweb orbweaver (Cyrtophora citricola, Fig. 4). Individuals of this species construct and maintain their own webs within a colony of interconnecting webs of neighboring conspecific spiders. The interconnected web mass can get rather large…a sight to behold! In one publicized instance, an old truck in the Tampa area was completely engulfed by the webbing.

ANTS, ANTS & MORE ANTS. Florida has its share of ants. They are considered the number one pest by many Florida pest management professionals. To add to the existing problem of controlling native ants, there are introduced species which some entomologists consider to be “supercolony” ants.

Figure 6. Southern yellowjacket, Vespula squamosa, caste series (top) and nest.
Top: Gerald Wegner. Bottom: Dale Richter

They include the:

  • African big-headed ant (Pheidole megacephala)
  • Argentine ant (Linepithema humile)
  • Difficult (white-footed) ant (Technomyrmex difficilis)
  • Tawny crazy ant (Nylanderia fulva)

Similarly, a native species known as the black pyramid ant (Dorymyrmex medeis, Fig. 5) has demonstrated the ability to form supercolonies on occasion. In certain documented Florida locations, these ants have been present in such high numbers, that it was nearly impossible to control them.

A MOSQUITO HAVEN. According to the University of Florida, our state is blessed with 80 known species of mosquitoes, 33 of them being a nuisance to us and other critters. The following list of species are known to transmit disease-causing pathogens, such as yellow fever, dengue, West Nile virus, Chikungunya virus and the Zika virus, and most recently, the Keystone virus:

  • Asian tiger mosquito (Aedes albopictus)
  • Eastern treehole mosquito (Aedes triseriatus)
  • Florida SLE mosquito (Culex nigripalpus)
  • Southern house mosquito (Culex quinquefasciatus)
  • Yellow Fever Mosquito (Aedes aegypti)
  • Aedes atlanticus

Florida also has the largest mosquito in the Southeast known as the Gallinipper, Psorophora ciliata. She is quite capable of delivering a painful bite right through clothing.

STINGING INSECTS. The predominant species of yellowjacket in Florida is the southern yellowjacket, Vespula squamosa. Because of Florida’s mild winters, nests of this species can continue to increase in colony size and volume perennially. Occasionally V. squamosa nests are reported and treated that contain hundreds of thousands of developmental cells and individuals, as well as multiple queens (polygynous, Fig. 6).

Figure 7. Arboreal-nesting conehead termites, Nasutitermes spp. nasutes and mud nest.

Like other areas of the United States, South and South Central Florida have seen an increase in Africanized honey bees (Apis mellifera scutellata), since they were first discovered at the Port of Tampa in 2002. They have been recorded in every county from Orange County southward. It is likely that AHB colonies exist in other Florida counties, as well.

HOW ABOUT WDOs? Florida has a reputation for termite diversity. It is known for its populations of native and introduced subterranean termites (Reticulitermes spp., Coptotermes spp., Prorhinotermes sp., Heterotermes sp., Amitermes sp.), dampwood termites (Neotermes spp.), and drywood termites (Incisitermes spp., Cryptotermes spp., Calcaritermes sp., and Kalotermes sp.).

Of particular interest is Florida’s very heathy population of the Formosan subterranean termite (Coptotermes formosanus), which continues to expand its distribution throughout the state. To add insult to injury, a close relative, the introduced Asian subterranean termite (Coptotermes gestroi) is making moves in Southeast Florida. Also, in May 2001 the arboreal-nesting conehead termite, Nasutitermes costalis (Fig. 7), was discovered in Dania Beach, also located in Southeast Florida. A related conehead termite, Nasutitermes corniger, found its way into South Florida some years later. Estimated costs of potential structural damage by these two species, should colony monitoring and destruction fail over the next decade, peak at about $9 million. It all comes down to more challenges for Florida professional applicators.

Figure 8. Camphor shoot borer, Cnestus mutilatus, and gnawing damage to plastic gasoline container.
Daniel D. Dye II

A wood-destroying organism (WDO) that has been on Florida pest management professionals’ radar since the late 1990s is the camphor shoot borer (Xylosandrus mutilatus/Cnestus mutilatus) (Curculionidae: Scolytinae). The camphor shoot borer is an invasive species from Asia. This tiny ambrosia beetle was first discovered in Mississippi in 1999. This pest is now found throughout North Central Florida as well as the Florida Panhandle. The beetles are attracted to ethyl alcohol fumes given off from gasoline storage containers, which they mistake for sweet gum and camphor trees — two of their host plants. When a host tree is damaged or stressed, it emits small amounts of ethanol, which attracts the borer… a case of mistaken identity. When camphor shoot borers land on a plastic gasoline container, they can gnaw tiny holes into it (Fig. 8) causing the container to leak. The result can be both costly and dangerous, posing both fuel contamination and fire hazards.

Also on the subject of wood-destroying organisms, pest management professionals from other states may find it curious that the Florida Department of Agriculture and Consumer Services (FDACS) categorize carpenter ants (Camponotus spp.) and carpenter bees (Xylocopa spp.) as “Non-WDOs.” The introduction to chapter 5, titled “Other WDO-like Organisms,” in the Wood-Destroying Organisms Applicator Training Manual (UF/IFAS Extension publication, first edition), explains that: “A number of arthropod species found in Florida qualify as WDO-like organisms in that they are known to cause superficial damage to wood, either before trees are milled into lumber or post-construction. In most cases the damage created does not pose a significant threat to the structural integrity of the wood in question. Certain ants, bees and other insects may excavate limited cavities in wood in which to rear their young, but do not utilize wood as a food source. Often the condition of the wood, having been exposed to moisture and fungal decay, is conducive to excavation by these organisms or has already become structurally compromised.”

Figure 9. Florida carpenter ant, Camponotus floridanus, major worker.
Gerald Wegner

In justification of this regulatory assessment, it must be said that the formidable-looking Florida carpenter ant, Camponotus floridanus (Fig. 9), and a similar species, Camponotus tortuganus, often relocate their colonies into existing concealed spaces in human structures but inflict little further excavation damage. Likewise, the southern carpenter bee, Xylocopa micans (Fig. 10), prefers to excavate its brood galleries in naturally occurring soft woody stems and branches, largely avoiding structural wood elements of buildings. The more destructive eastern carpenter bee, Xylocopa virginica, is not pervasive in Florida. Perhaps the Florida non-WDO stand on ants would need to be reconsidered if more aggressively damaging species like the eastern black carpenter ant, Camponotus pennsylvanicus, and western black carpenter ant, Camponotus modoc, were widespread in the state.

Figure 10. Southern carpenter bee, Xylocopa micans, female.
Gerald Wegner

WHAT LIES AHEAD? Florida applicators seem resigned to the fact that sporadic, irresponsible or uncontrollable introduction of arthropods from the Caribbean, Central America and Southeast Asia is a certainty. One can only speculate how climate change might affect pest populations in Florida. There are reports by meteorologists that Florida has dodged its normal onslaught of hurricanes during the past few years and that more frequent hurricanes are to be expected. That being the case, perhaps more arthropods now in Florida may be carried or driven into neighboring states to the north. Whatever the future holds, there would appear to be job security for pest management professionals coast to coast.

Dye is an ACE emeritus who was training coordinator for Florida Pest Control, Gainesville, Fla. Schappert is owner of The Bug Doctor, Ocala, Fla. Wegner is a consulting entomologist and former technical director of Varment Guard, Columbus, Ohio.