Ravenous Formosan subterranean persist in California

Michael K. Rust u Donald A. Reierson 0 Eileen 0. Paine David Kellum u Karl Haagsma

In February 1992, Formosan subterra- merce (Su and Tamashiro 1987). In the nean was discovered in La United States, C.forrnosanus is a major Soldiers are distinguished by the dark Mesa, a residential community ap- structural pest in Hawaii and is estab- head capsule and long mandibles. Work- lished in at least seven southeastern ers hatch from eggs laid by the queen and proximately 10 miles east of San Di- are the only stage that feeds on wood. ego. The infestation was estimated to states, where it causes extensive dam- Colonies can attain 2 million workers be approximately 10 years old age. It is becoming increasingly eco- within 5 years. (Atkinson et al. 1993). This age corre- nomically important wherever it has sponds to a time that a family living at become established. It is currently the the epicenter of the affected area most destructive termite in Florida The first reported case of a non- brought wood and potted plants with and Louisiana. Once established in an native termite being them when they moved from Hawaii. area, C.formosanus can exact tremen- introduced and established in Formosan subterranean termite is dous damage within a relatively short California was the Formosan common in Hawaii, and one or more time. Large colonies have reportedly subterranean termite, which was colonies were probably transported to caused significant damage to homes discovered in San Diego County California in the family’s belongings. within 6 months of detection, and in 1992. Because this termite can This species was misidentified for sev- have rendered homes unlivable within exact tremendous damage within eral years after its introduction. We 2 years. Besides attacking homes, C. a relatively short time, the af- documented Formosan subterranean fomosanus also ravages utility poles, fected area was defined and an termite from seven adjacent core area boats and even dead portions of living attempt was made to eradicate it. properties in La Mesa. trees. In 1995 we reported that the Intensive baiting with the Termite life cycle growth regulator hexaflumeron Formosan subterranean termite, over 12 months appears to have formosanus Shiraki, had be- Like other termites, the Formosan eliminated the original infesta- come established in La Mesa subterranean termite is a social insect tion. New infestations have re- (Haagsma et al. 1995).Since then, we living in colonies with a division of la- bor between specialized castes. cently been discovered in and have eliminated the original termite c. infestation, but the termite appears to formosanus typically nest in the around homes about 1/4 mile have spread to an adjacent area before ground, but sometimes build aerial away, and winged Formosan elimination was complete. As with vir- colonies with no ground contact if suf- subterranean termites have been tually all species of termites, the liid- ficient water is available. They have caught nearly 3/4 mile away. den nature of young C. forrnosanus even been found flourishing in Florida Measurements of workers and colonies makes them especially diffi- and Hawaii on the rooftops of high- soldiers and dating of damage cult to detect and identify. Damage by rise apartment buildings. suggest that the new colonies young colonies is often localized and Seasonally, new kings and queens are 6 to 8 years old, and that new may go unnoticed for years. form as the colony matures. Winged colonies estabhshed from males (kings) and females (queens) winged reproductives before Distribution and impact from the same or different colonies baiting took effect at the original The Formosan subterranean termite leave the nest to mate and begin a new site. If left unabated, this pest is native to mainland China and has colony. These new reproductives are may become increasingly more spread to tropical and subtropical ar- tan in color, have long wings, and are serious in California. eas of the world, primarily by com- called alates. As with most termites,

34 CALIFORNIA AGRICULTURE, VOLUME 52, NUMBER 2 Termite damage to a large beam that sup- ported the floor of an infested home at La Mesa. Large colonies have reportedly ren- dered homes unlivable within 2 years.

only a small fraction of the alates that leave the colony are successful at start- Damaged beams and Formosan termite ing new colonies. carton (nest) in box. In San Diego, sporadic mating flights of C. formosanus occur from May to September. They always occur Subsequent monthly ground sur- in the early evening and on days dur- veys and monitoring with sticky traps ing which the daytime temperature ex- for alates and with wood stakes for ceeds 88°F (31.1"C). Workers hatch workers suggest that the baiting elimi- from eggs laid by the queen and are nated C. fo~mosanusfrom the originally the only stage that feeds on wood. affected area. Colonies can attain 2 million workers Baiting has the advantage of mini- within 5 years (Higa 1981). Like most mizing pesticide use. A termite colony species of termites, C. formmanus also is killed if worker termites feed on has a defensive caste called a soldier. strategically placed bait and pass it among themselves and to the queen Effect of bait and soldiers. Conventional liquid ter- A new bait formulation (Recruit) mite treatments kill only the termites found to be highly preferred by C. that they contact, and they protect foymosanus in other parts of the coun- structures by providing a repellent try was substituted for the original and toxic barrier. bait reported by Haagsma et al. (1995). A small amount of foraging on The original bait was fed upon to hexaflumeron bait may be sufficient to some extent by termites in La Mesa, eliminate a termite colony. Since Wood damage and typical mud carton ma- terial packed in the wood by Formosan but the new formulation was clearly hexaflumeron is slow acting, affecting subterranean termites. more palatable. Bait containing 0.5% the when they molt, feeding on hexaflumeron - an insect growth the bait may continue long after the regulator that prevents termites from amount needed to kill the colony has developing new cuticle at the time of been consumed. In Florida, an esti- molting - was presented in four mated population of 1.2 million ground stations and two stations in an Formosan subterranean termites was infested mature pepper tree from late eliminated after feeding on only 51.8 February to July 1996. There was ter- grams of bait (259 mg ai), and a popu- mite feeding in all six stations. During lation of the eastern subterranean ter- these 5 months, the termites consumed mite, flavipes (Kollar), es- a total of 360 grams of bait (I.8 g active timated at 476,000 individuals, was ingredient). By July 23, no termites eliminated with as little as 0.8 grams could be found at any bait station, of bait (Su 1994). trap, nor other location within the core Determining the effectiveness of area of the seven properties on which C. control of subterranean termites is Cut firewood infested with Formosan formosunus was originally found in 1992. problematic because of the highly sea- termites.

CALIFORNIA AGRICULTURE, MARCH-APRIL 1998 35 colonies in that area were eliminated since 1993, in spite of more intensive or have been suppressed to such an trapping between 1994 and 1997. This extent that they have been undetect- reduction is consistent with the less- able for many months. ened foraging activity in our ground However, finding a colony outside traps, and is an indication of the im- \ NA12 the baited area is disconcerting be- pact of hexaflumeron bait in the origi- 711 cause it suggests that sources of infes- nal epicenter of infestation. We have tation persist nearby. examined alate trap data by quadrants and distance from the original infesta- Trapping alates tion because of the discovery of a sec- Beginning in 1992, swarms of alates ond established population of C. of C. formosanus were monitored in La formosanus recently found nearby, but Mesa with sticky traps hung on porch outside our baited and monitored lights at 10 homes near the site where area. N t the termites were first discovered. We collected C. formosanus alates in Alates tend to fly to lights in the early light traps as far as 0.7 miles from the evening. We expected most alates to original infestation. Light traps are ap- be caught on traps nearest the center parently more effective at trapping of infestation. Alate monitoring in swarming C. formosanus than are Fig. 1. Distance and direction of light traps from the original infestation and the num- 1993 was expanded to include 69 sticky traps. It is likely that new repro- ber of alate Formosan subterranean ter- properties. In 1995, commercial fluo- ductive pairs may have established mites trapped in 1995 and 1997. NA = not rescent light traps for insect collection themselves in at least a 3- to 5-square- available; 1995/1997. were installed at each of four sentinel mile area of La Mesa. locations about 1/2 mile from the af- In 1997, the number of alates fected homes, in locations where alates trapped outside the core baited area sonal and cryptic nature of termites. from the epicenter would have a good dramatically increased, suggesting Damage often goes undetected. We chance of encountering the traps. In other active C.forrnosanus infestations have been further hampered at the La 1997, we added another four light (table 1). A new infestation was lo- Mesa site because we had no precise traps some of which were up to a mile cated approximately 200 feet beyond a pretreatment population estimates. away (fig. 1). steep, granite rock hillside north of the Despite extensive monitoring with up Continuous monitoring of tempera- core area. The geological separation to 100 wooden stakes driven into the ture, humidity and rainfall was done between sites makes it unlikely that ground on the property and around in La Mesa since 1993 and we corre- the new infestation was ever directly each home where alates were cap- lated alate trap catch to that monitor- connected with the original colony. It tured, less than 3% of the stakes were ing. Figure 2 shows alate trap counts is likely that the new colony is a sec- ever attacked by termites. Sticky cards and average monthly maximum tem- ondary infestation resulting from alate and light traps were more useful tools peratures in La Mesa for selected dates swarming from the original area. A to locate new or previously undetected during the study in the core area. infestations. Major swarming of C. Trapping data suggested the pres- forinosanus occurred in June or 2,000 ence of a second ground infestation at July, only when daytime tem- least 1 year before the infestation was peratures exceeded 88°F discovered. Thus, the success of bait- (31.1"C) . There was no rela- ing was judged by visual inspection, tionship to rainfall. Lesser the lack of termite activity in the area, swarming events occurred for and a decrease in the number of alates up to 5 months following the trapped. major swarm. After finding no C. formosanus activ- Initial analysis from the ity for several months within the original isolated infestation on baited area, a colony was discovered seven properties showed that in November 1996 approximately 1/4 most trapped alates were 8888zzx%888~88816666 mile from the original infestation, just caught within 500 feet of 5 $rg$ $78 $$;g$$;g beyond the border of the area we were where they emerged, but a monitoring. The fact that we continue few were caught up to 900 feet Fig. 2. The number of alate Formosan sub- terranean termites trapped in La Mesa to find no C. formosanus in the original away. The number of dates collected within a 2OO-yard radius of the original baited area strongly suggests that in the core area has steadily declined infestation.

36 CALIFORNIA AGRICULTURE, VOLUME 52, NUMBER 2 pest control operator who first found the secondary population indicated the termites had actually been active in the structure nearly 2 years before our application of bait material in the nearby core area. The worker termites (3.39 k 0.404 mg, n = 72) from the new find are significantly smaller than similar stages collected from the original core area (4.27 k 0.09 mg, n = 50, Atkinson et al. 1993; t-test, ts = 50.29, P < 0.02). Besides the differ- ence in worker size (Grace et al. 19951, the long distances between properties where alates have been re- cently captured suggest that there are at least two colonies in the same neighborhood. At this point at least five homes in the new infestation area have been damaged by C.formosanus. Damage to some has been extensive, with treat- ment and repair costs totaling tens of thousands of dollars. All five homes station. have been fumigated for above- ground C. formosanus. The homes have also received ground treatment with termiticide and have had commercial bait installed. An effective remedial Entomology, UC Riverside; D. Kellum is strategy to eliminate Formosan subter- Senior Economic Entomologist, Depart- ranean termites in California has not inent of Agriculture, San Die20 County; References yet been developed. Our research pro- and K. Haagsma is cuvreiztly working as gram in Mesa has been discontin- Atkinson TH, Rust MK, Smith JL. 1993. La a private consultant to the pest control The Formosan subterranean termite, ued owing to lack of funding. How- industry. Copfofermes formosanus Shiraki (Isoptera: ever, alate monitoring should be The authors would like to thank Joy ), established in California. continued and expanded to detect the Murray-Roseberry, Tim Breuninger and Pan-Pac Entomol 69: 11 1-13. Grace JK, Yamarnoto RT, Tamashiro M. geographic spread of this destructive Cathymay Mangold with the County of 1995. Relationship of individual worker mass pest and to serve as an early warning San Diego, Department of Agriculture for and population decline in a Formosan subter- system to alert homeowners and pro- theiv assistance in monitoring. We thank ranean termite colony (Isoptera: Rhino- fessional pest control operators of im- Chief Chris Carlson of the City of La Mesa ). Environ Entomol 24: 1258-62. Haagsma K, Rust MK, Reierson DA, pending problems. Fire Department for the 1997 weather data Atkinson TH, Kellum D. 1995. Formosan sub- for La Mesa. terranean termite established in California. M.K. Rust is Professor and Entomologist, They also thank DowElanco for prouid- Cal Ag 49: 30-3. Higa SY. 1981. Flight, colony foundation, and D.A. Reierson and E.O. Paine are ing financial support and the hexaflu- and development of the gonads of the pri- Staff Research Associates, Department of meron bait used in the studies. mary reproductives of the Formosan subterra- nean termite, Copfofermes formosanus Shiraki. TABLE 1. Number of Formosan subterranean termite alates trapped within and beyond 200 yards of Ph. D. diss., Univ. Hawaii, Honolulu, HI. the original infestation in La Mesa Su N-Y. 1994. Field evaluation of a hexaflumeron bait for population suppression Core area (5 200 yards) Outside the core area (> 200 yards) of subterranean termites (Isoptera: Rhino- No. No. traps No. No. traps termitidae). J Econ Entomol 87: 389-97. Year No. tram alates with alates No. tram alates with alates Su N-Y, Tamashiro M. 1987. An overview 1993 41 2,206 30 - - - of the Formosan subterranean termite 1994 40 1,840 33 54 627 44 (Isoptera: Rhinotermitidae) in the world, 1995 35 875 25 49 703 30 p 3-1 5. In M Tamashiro and N-Y Su (eds.), 1996 36 544 16 49 93 17 Proceed. Int. Symp. on the Formosan subter- 1997 17 113 8 42 2.535 26 ranean termite. Hawaii Institute of Trop. Core area defined as within 200 yards of the original (1992) identified site of infestation. Agric. and Human Resources, Research Ext. Series 083.

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