A System for Elimination of
Subterranean Termite Colonies
Nan-Yao Su and Rudolf H. Scheffrahn
University of Florida, Ft. Lauderdale Research and Education Center
3205 College Avenue
Ft. Lauderdale, FL 33314
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Of the approximately $1.5 billion spent annually for termite control in the U.S., subterranean termites account for an 80% share. Triple mark-recapture programs using dye markers such as Sudan Red 7B Figure 1 revealed that a single subterranean termite colony may contain millions of foragers and may forage a distance of up to 300 ft (Su and Scheffrahn 1988, Grace et al. 1989, Su et al. 1993). A large subterranean termite colony, therefore, may inhabit large areas of soil beneath an infested home Figure 2A . Conventional soil termiticides have been used for the last four decades to provide a chemical barrier for the exclusion of soil-borne termites from a structure Figure 2B . Typically, 100 - 200 gal. of liquid termiticide (8 - 17 lb. active ingredient @ 1% concentration) are applied in the soil beneath and surrounding an infested home (NPCA 1985). The vast proportion of subterranean termites, however, are not affected by such soil termiticide treatment Figure 2B . These termites often find their way back into the structure, causing costly re-treatment (Su and Scheffrahn 1988).
Population studies for field colonies of subterranean termites indicated that wooden stakes placed near a large colony of these cryptic insects are eventually attacked by termites. Slow-acting and non-repellent toxicants may be incorporated into such food sources to affect the vast population of the subterranean termite colony (Su et al.1982) Figure 2C . Through an extensive laboratory screening program (Su and Scheffrahn 1993), we discovered that a chitin synthesis inhibitor, hexaflumuron, interfered with the molting process of both the Formosan subterranean termite, Coptotermes formosanus, and the eastern subterranean termite, Reticulitermes flavipes Figure 3 . A baiting procedure that incorporated a matrix containing hexaflumuron was evaluated against field colonies of the Formosan and eastern subterranean termites (Su 1994a). Wooden stakes were first driven into soil to detect the presence of termites. Bait tubes were placed in the soil where termites were detected. The results demonstrated that approximately 4 - 1,500 mg (less than 1/20 oz.) of hexaflumuron was needed for 90 - 100% reduction of field populations containing 0.5 - 2.8 million eastern subterranean termites per colony Figure 4 , and 1.0 - 2.4 million Formosan subterranean termites per colony Figure 5 . Elimination of colony populations created a zone of termite-free soil surrounding a home for several years (Su 1994b).
Following the success of the initial field trials, a prototype monitoring/baiting station was designed for commercial application Figure 6 . The station containing the monitoring device is first installed in soil surrounding a home Figure 7A . When termites are found in the station Figure 7B , the monitoring device is replaced with a tube containing bait laced with a minute amount of hexaflumuron Figure 7C . Termites collected from the monitoring device are dislodged into an empty space on the top of the tube, called the "recruiter's chamber." Figures 7C, D
Termites placed in the recruiter's chamber have to feed their way out of the bait to reunite with nestmates Figures 8A, B . Left behind in the bait are their species- and colony-specific odors Figure 8C . One of such chemicals is the trail-following pheromone excreted from the sternal gland Figure 9 , which guides nestmates to the bait. This self-recruitment procedure enhances bait uptake by termites (Su 1994a). Hexaflumuron kills insects only when they molt every 1 - 2 months. During this period, the bait is thoroughly distributed throughout the colony populations. The monitoring/baiting system is currently commercialized under the Sentricon® brand name by DowElanco (Indianapolis, IN), who invented and owns the proprietary rights to hexaflumuron. Field trials using the system typically require less than one gram (0.04 oz.) of hexaflumuron to eliminate field populations of several million termites (Su et al. 1995) Figure 10 .
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Su, N.-Y. and R. H. Scheffrahn. 1993. Laboratory evaluation of two chitin synthesis inhibitors, hexaflumuron and diflubenzuron, as bait toxicants against Formosan and eastern subterranean termites (Isoptera: Rhinotermitidae). J. Econ. Entomol. 86: 1453-1457.
Su, N.-Y., M. Tamashiro, J. R. Yates and M. I. Haverty. 1982. Effects of behavior on the evaluation of insecticides for prevention of or remedial control of the Formosan subterranean termite. J. Econ. Entomol. 75: 188-193.
Su, N.-Y., P. M. Ban and R. H. Scheffrahn. 1993. Foraging populations and territories of the eastern subterranean termite (Isoptera: Rhinotermitidae) in southeastern Florida. Environ. Entomol. 22: 1113-1117.
Su, N.-Y., E. M. Thoms, P. M. Ban and R. H. Scheffrahn. 1995. A monitoring/baiting station to detect and eliminate foraging populations of subterranean termites (Isoptera: Rhinotermitidae) near structures. J. Econ. Entomol. 88: 932-936.