Natural overwater dispersal of infested flotsam and anthropogenic dispersal by maritime vessels are the 2 primary means by which termites are transported across distant sea barriers (Scheffrahn et al. 2009). The cessation of rapid late Pleistocene/Holocene sea level rise at about 7K years before present (ybp, Fleming et al. 1998) predates the first known long-distance human maritime voyages by some 3.5K ybp (Anderson et al. 2006). Therefore, contemporary nonathropogenic termite distributions were established between these 2 periods. Distant termite dispersal by flotsam can be presumed to be a very rare event with a success rate inversely proportional to distance. Establishment of the depauparate native terrestrial faunas on distant oceanic volcanic islands such as Hawaii was the result of transoceanic dispersal (Cowie & Holland 2006). Nearshore islands like the Krakatau can be colonized much more frequently by both flotsam transport and cross-water termite dispersal flights (Gathorne-Hardy & Jones 2000).

Shipboard transport of termite colonies, where success is not affected by travel distance, has been suspected in recent (Gay 1967; Scheffrahn & Su 2005) and early (Scheffrahn et al. 2009) transoceanic termite establishments. Vessels can be colonized during construction (usually only Kalotermitidae) or by alates (all taxa) flying onboard during dockage, either on water or in dry dock. Hochmair & Scheffrahn (2010) showed a strong correlation between land-borne infestations of Coptotermes spp. in Florida and their distance to maritime boat dockage suggesting that marine vessels are predominant vehicles for dissemination of this pest genus.

Within the last century, 6 exotic termite species have become established in Florida (Scheffrahn et al. 1988; Scheffrahn et al. 1992; Scheffrahn et al. 2002; Scheffrahn & Su 1995; Su et al. 1997), more than any other state or territory in America, followed by Hawaii with 5 species (or 4 species if Zootermopsis angusticollis Hagen is not established, Woodrow et al. 1999; Yeap et al. 2007). Australia has a slightly greater human population than Florida, a much larger tidal coastline, and both share similar economies, climates, pleasure boating industries, and proximities to tropical nations to the north and south, respectively. Yet, in the last century, a single exotic termite, Cr. brevis (Walker), has become established in Australia (Peters 1990). As for other suspected exotic Cryptotermes, Gay & Watson (1982) determined that Cr. cynocephalus Light and Cr. domesticus (Haviland) are endemic to northeast Australia. Gay (1967) reported that Cr. dudleyi Banks, an exotic drywood termite from Southeast Asia, was already established in Darwin by 1913.

In a further attempt to understand the dynamics and taxa involved in exotic termite establishments, we provide a summary of onboard termite infestations in Florida and border interceptions in Australia and we contrast the regulatory procedures used for boats arriving from foreign ports.

MATERIALS AND METHODS

Termite specimens from Australia were found during interceptive inspections by WC and other Australian Quarantine and Inspection Service (AQIS) personnel. Florida samples were collected by or submitted to RHS by pest control professionals and boat owners or operators. In both cases, onboard specimens were collected and stored in ethanol. Identifications were made by the authors using voucher specimens from their respective collections. Other information sought included date of collection, given in Table 1 only in years, location collected (city), vessel origin (if known), and vessel and/or infestation type. For species identification, samples were required to contain morphologically robust winged imagos and/or soldiers. Workers were identified morphologically only to genus.

RESULTS AND DISCUSSION

During 1986–2009, 74 and 59 termite incidents onboard boats were recorded in Australia and Florida, respectively (Table 1). The Australian records are comprehensive and represent all known AQIS interceptions. The Florida incidents represent an informal and very incomplete sampling of the actual number of boat infestations occurring around the State. Three vessels were infested simultaneously by 2 species and each is recorded as a separate incident in Table 1. Unlike Australia where only Cr. brevis is established, most boats in Florida are infested in their home waters where exotic species abound. This phenomenon enhances the spread of termites in Florida from boat-to-land or land-to-boat by dockside dispersal flights and also elevates the likelihood that boats voyaging from Florida could spread termites to foreign ports. Although long, open ocean voyages are not the norm for Florida boaters, some will “island-hop” throughout the West Indies. One yacht, suspected of acquiring Co. gestroi Wasmann (= havilandi, Kirton & Brown 2003) during a winter dockage in the Turks and Caicos Islands (Scheffrahn & Su 2005) was simultaneously infested with Incisitermes minor (Hagen). It was presumed that the latter species infested this boat while under construction in San Diego, California.

The subterranean genus Coptotermes (Family Rhinotermitidae) was observed in 53% of all boat infestations (Fig. 1) with Co. formosanus Shiraki being the most common onboard pest in both Florida (27 records) and Australia (13 records) followed by Co. gestroi with 15 and 4 records, respectively. Three other infestations by subterranean termites were recorded including 2 by Reticulitermes virginicus (Banks) in Florida and 1by Heterotermes sp. in a boat that sailed from Florida to Grand Cayman Island. The second most prevalent genus, at 30% of boat infestations, was Cryptotermes (Family Kalotermidae). Australian interceptions yielding 8 infestations each of Cr. brevis (Walker) and Cr. domesticus (Haviland), 3 infestations of Cr. dudleyi Banks, 2 of Cr. cynocephalus Light, and 15 Cr. species undetermined. Only 3 infestations of Cr. brevis were recorded from Florida; however, fumigations for this species are so routine in Florida that samples are seldom collected for identification. One pest control company in Fort Lauderdale estimates that it is contracted to fumigate about 15 boats a year for drywood termites (read Cr. brevis, Edwards, J. K., personal communication). On the other hand, 6 infestations of I. minor were recorded in both Australia and Florida. Alates of I. minor are much more robust and dark (reddish pronotum and head) than Cr. brevis and have a different flight season and diel periodicity. Therefore, I. minor flights prompt elevated identification requests by the Florida pest control industry. Australia recorded a single shipboard infestation each of I. immigrans (Snyder) and I. sp., while in Florida, a single infestation of I. snyderi (Light) was observed on a houseboat in Key West. The most unexpected find of this study was a mature infestation in 2009 of Rugitermes panamae (Snyder) from an itinerant yacht intercepted while visiting Bundaberg Australia. The yacht was apparently infested by this “dampwood” species during a voyage in 2003 to Central America. Colonies of the predominantly arboreal genus Nasutitermes (Termitidae) were found on boats 3 times during the last 25 years. Nasutitermes acajutlae (Holmgren) was found twice and N. nigriceps (Haldeman) once in Florida. Although not recorded in Table 1, N. corniger (Motschulsky) was found infesting 2 boats in dry dock in Dania Beach, Florida, as part of a land-borne infestation of this pest (Scheffrahn et al. 2002).

We suggest herein that the difference in the number of exotic termite species established in Florida versus Australia is attributable, at least in part, to differing laws and regulations intended to exclude exotic pests. The U.S. Customs and Border Patrol (CBP) requires that pleasure vessels arriving in the U.S. from a foreign port must report their arrival by telephone and be directed, with passengers and crew, to the nearest port of entry or nearest designated reporting location for a CBP face-to-face interview and/or vessel inspection (Anonymous 2009). Inspections focus on immigration compliance by the passengers and crew, possible illegal contraband, and agricultural pests in cargo. Structural and household pests, which are usually disassociated with cargo and dwell within the vessel's own structure, are not mandated for inspection. In contrast to Florida practices, passengers and crew aboard vessels arriving to Australia from a foreign port must obtain clearance by the Australian Customs and Border Protection Service and the Australian Quarantine and Inspection Service (AQIS). Vessels with timber in their cargo or construction must also be inspected by AQIS. The level of AQIS inspection required will depend on the amount of timber present and the construction/re-fit and sailing history of the vessel. The inspection can be conducted by an AQIS quarantine officer or AQIS entomologist with or without a licensed pest control professional and approved termite detection method. If termites are found upon inspection, the vessel must be fumigated with methyl bromide (AQIS method T9047) or sulfuryl fluoride (AQIS method T9090) at the owner's expense (Anonymous 2010).

TABLE 1.

TERMITE INFESTATIONS BY GENUS AND SPECIES ONBOARD VESSELS DURING 1986–2009 (VOUCHER SPECIMENS IN THE UNIVERSITY OF FLORIDA TERMITE COLLECTION OR AQIS RECORDS).

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Fig. 1.

Frequency of termite genera collected on vessels in Australia and Florida. “Other” includes Drepanotermes and Rugitermes from Australia and Heterotermes from Florida.