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FACTORS AFFECTING TERMITE RECRUITMENT TO BAITS IN DEBORAH A. WALLER, SUSAN E. MORLINO, AND NICOLE MATKINS Biology Department, Old Dominion University, Norfolk, Virginia 23529 USA Abstract - A weak link in the implementation of effective termite baiting techniques is reliable recruitment of termite
foragers to baits. Little is known about how termites locate food sources, but many factors may influence whether for-
agers find and recruit to a given bait. These include the abundance and palatability of the bait relative to alternate foods
in the habitat, chemical directional clues to the location of food in the soil environment, and the presence of predators
and termite competitors at the bait site. We have investigated these factors in the subterranean termite Reticulitermes
(Isoptera: Rhinotermitidae) over the past five years in laboratory and field studies in Virginia. In the laboratory, termites
recruited in higher numbers to substrates drenched with solutions of sucrose and yeast or urea than to water-drenched sub-
strates. In field studies, more termites occupied baits covering drenches of sucrose + yeast or urea solutions than baits cov-
ering water drenches. Some baits contained ant predators. Reticulitermes flavipes and Reticulitermes virginicus usually
fed on separate baits, but once R. flavipes appeared to be displaced by R. virginicus. These results suggest that numerous
bait monitoring stations should be placed near structures to ensure that all local colonies have an opportunity to sample
baits. Continued experimentation with drenches is likely to yield a recipe that reliably draws termite foragers to baits.
Key words - Foraging, Reticulitermes, sucrose, urea
INTRODUCTION
A promising new focus in termite control involves baits that deliver toxicants to termites (French, 1994).
The objective is to draw termite foragers to a palatable bait laced with toxicant; foragers are expectedto distribute the toxicant to nestmates, resulting in the elimination or suppression of the colony. The weaklink in this chain is the recruitment of termites to the bait. Factors that may affect termite recruitmentinclude the amount of bait and its palatability relative to other foods in the habitat, chemical directionalcues to the location of the bait in the soil environment, and the presence of predators and termite com-petitors at the bait site.
No reliable techniques have been developed to ensure that termites locate baits, because little is known about how termites find food in nature. One possibility is that foragers follow subterranean con-centration gradients of chemicals leached from rotting wood. We examined this idea by testing termiteresponse to chemicals and their leachates in laboratory and field tests. We focused on solutions contain-ing sucrose and yeast and urea (Waller, 1996). Sucrose is found in decomposing wood (Anderson, 1962),and yeasts are widespread in woody debris and soil. Urea occurs in fungi (Martin, 1979), which arefrequently consumed by termites in decayed wood (Waller et al., 1987).
MATERIALS AND METHODS
Termite collections
Reticulitermes (Rhinotermitidae) colonies were collected from southeastern Virginia. Both Reticuli-
termes flavipes
Kollar and Reticulitermes virginicus Banks were collected and used in experiments.
Termites were maintained in the host log in the laboratory at 22 °C up to 24 h prior to experiments.
Sucrose and yeast
Each laboratory test unit consisted of three connected clear plastic chambers, each 12.5 cm x 10 cm x
x 1.0 cm. Clear plastic tubing connectors allowed free movement among chambers. We placed 50 cc
vermiculite and 25 ml solution in each chamber. The central chamber and one side chamber contained
Proceedings of the 3rd International Conference on Urban Pests.
Wm H. Robinson, F. Rettich and G.W. Rambo (editors). 1999. Deborah A. Waller, Susan E. Morlino, and Nicole Matkins distilled water, and the other side chamber contained 1% (w/v) yeast in 1% (w/v) sucrose solution. Twohundred termite workers and four soldiers were added to the central chamber. After 3 d at 22 ºC, num-bers of termites in each chamber were counted. Three colonies (two R. flavipes and one R.
virginicus
) were tested with two replicates per colony.
Field experiments were performed at Old Dominion University’s Blackwater Ecological Preserve (BEP), a 130 hectare pine forest in Zuni, Virginia. Both Reticulitermes flavipes and R. virginicus arecommon at the site. Three parallel 130 m transects were set 10 m apart with baits placed every 10 m(total 42 baits). Baits consisted of rolled cardboard secured with a pine stake and covered with a plasticpot. We poured 4 l of solution under each bait, alternating drenches of distilled water and solutions of 1%(w/v) yeast in 3% (w/v) sucrose solution. Baits were checked for termites at 1, 4 and 6 weeks later.
Urea
Laboratory experimental units consisted of a central 40 cc round plastic chamber attached by clear plas-
tic tubing to four identical chambers. The central chamber was filled with 30 cc sand and 15 ml distilled
water; the attached chambers contained 40 cc sand and 10 ml of either 1% urea solution
(2 chambers) or distilled water (2 chambers). We placed 20 termites in the central chamber and allowed
them to forage through the tubing and into the attached chambers. Numbers of termites entering the
urea- or water-drenched chambers were recorded at 3, 6, 9, 12, 15, 30 and 1,440 min. Ten colonies (five
R. flavipes and five R. virginicus) were tested with 3 replicates per colony.
The field experiment was performed at BEP, at a different location from the sucrose experiment.
Two sets of transects were established, each with five parallel 100 m transects set 10 m apart, with baits(a pine stake next to a pine shim pack) placed every 10 m (total 100 baits). We poured 4 l of solution undereach bait, alternating drenches of well water and 1% urea solutions. Baits were checked for termites at4, 5, 6 and 7 weeks.
Data analysis
Laboratory data were statistically analyzed using analysis of variance. Field data were not analyzed due
to the low numbers of termites present in the baits.
Sucrose and yeast
In the laboratory experiment significantly greater numbers of termite workers recruited to the sucrose
and yeast chambers than remained in the central chamber or recruited to the water-drenched chambers
(ANOVA, F = 27.273, p = 0.0001). There were also significantly greater numbers of soldiers in sucrose
+ yeast chambers than in the others (ANOVA, F = 24.5, p = 0.0001) (Table 1). R. flavipes and
R. virginicus showed similar responses.
Table 1. Mean + SE numbers of termite workers and soldiers in the central chamber, and chambers
drenched with 1% (w/v) sucrose and 1% (w/v) yeast solution or distilled water. Each unit initially had 200
workers and 4 soldiers introduced to the central chamber. Units were maintained for 3 d in the laboratory
at 22 ºC.
Proceedings of the 3rd International Conference on Urban Pests.
Wm H. Robinson, F. Rettich and G.W. Rambo (editors). 1999. Factors affecting termite recruitment to baits in laboratory and field studies Table 2. Number of baits occupied by termites after 1, 4 or 6 weeks in field experiment. Baits covered
drenches of 4 l of either 3% (w/v) sucrose and 1% (w/v) yeast or distilled water.
Table 3. Mean ± SE number of termites entering chambers drenched with solutions of 1% urea or dis-
tilled water over time. Twenty termites were introduced in a central chamber and observed over 1,440
minutes. Ten colonies with three replicate units per colony were tested.
Table 4. Number of baits occupied by termites after 4, 5, 6, 7, and 8 weeks in field experiment. Baits
covered 4 l drenches of either 1% (w/v) urea or distilled water.
After one week in the field experiment, eleven sucrose + yeast baits contained termites, and four water baits had termites. In weeks 4 and 6, however, the numbers of sucrose + yeast baits and waterbaits with termites were similar (Table 2). Over the six-week period, a total of 13 sucrose + yeast-drenchbaits and 13 water-drench baits were occupied by termites. Four sucrose + yeast-drench baits containedR. flavipes initially (one of these was taken over by R. virginicus), and R. virginicus occupied 10 baits.
Two water-drench baits contained R. flavipes, and 11 contained R. virginicus.
Urea
In the laboratory experiment significantly greater numbers of termites recruited to the urea-drenched
chambers than to the water-drenched chambers (Repeated measures ANOVA, F = 4.15, p = 0.0483).
Proceedings of the 3rd International Conference on Urban Pests.
Wm H. Robinson, F. Rettich and G.W. Rambo (editors). 1999. Deborah A. Waller, Susan E. Morlino, and Nicole Matkins Numbers of termites increased in both chambers over time (F = 24.264, p = 0.0001) (Table 3).
R. flavipes and R. virginicus showed similar responses. In the field experiment more urea-drench baitswere occupied by termites than water-drench baits, but there was little recruitment to any bait (Table 4).
Four urea-drench baits contained termites (three with R. virginicus and one with R. flavipes), and twowater-drench baits contained termites (both R. virginicus). Ants were found in two urea-drench baits,one without termites and one with R. flavipes.
DISCUSSION
The foraging biology of termites is poorly known (Curtis and Waller, 1997). Our laboratory experimentsdemonstrated that the subterranean Reticulitermes can detect chemcial drenches in the substrate andwill move towards both urea solutions and sucrose + yeast solutions. In nature, urea, sucrose and yeastare likely to be encountered by termites in the soil and decayed wood in much lower concentrations thanthose tested here (Anderson, 1962; Martin, 1979). Whether these chemicals help termites locate nat-ural food sources is unknown. However, our results indicate that urea and/or sucrose and yeast solutionshave the potential to draw termites to bait stations. In the field, more baits on urea and sucrose and yeastsolution drenches were occupied than baits on water drenches, but the results were not as strong as inthe laboratory. Many factors may account for the weaker response in the field. First, termites in a pineforest have an abundance of alternate foods, perhaps more palatable than the treatment solutions. Sec-ond, the dense mosaic of chemical traces in soils may have interfered with the termites’ detection of thesucrose + yeast and urea solutions. Third, the soil water content at the time of the experiments may haveinfluenced whether or not termites responded to the water drench. During dry seasons, water drenchesalone may draw termites to a bait. Fourth, microbial activity in the soil may have altered the chemistry ofthe solutions.
Ant predators were present in one termite-occupied bait. We have often found ants and termites together in logs and in other bait studies, but ants rarely appear to interfere with termite activity (Waller,personal observation). However, it is possible ants influenced the low number of baits occupied by ter-mites. More baits were occupied by R. virginicus than R. flavipes, and we noted one instance whereR. virginicus appeared to take a bait from R. flavipes. In laboratory competition experiments (Math-ews and Waller, unpublished), R. flavipes controlled the bait in some outcomes, and R. virginicus con-trolled the bait in others. These results suggest that baiting regimes should include numerous bait stationsso that all local species have an opportunity to sample baits. More research on recipes for drenches andthe influence of predation and competition on bait occupation will be valuable in the development ofeffective baiting programs for termites.
ACKNOWLEDGMENTS
This research was supported by National Science Foundation award DEB-9220857 to DAW. We aregrateful for the use of the Blackwater Ecological Preserve for field studies.
REFERENCES CITED
Anderson, A. B. 1962. On the chemistry of wood rot. TAPPI 45: 40-60.
Curtis, A. D. and D. A. Waller. 1997. Problems with the interpretation of mark-release-recapture data in subterranean ter- mites (Isoptera: Rhinotermitidae). Sociobiology 30: 233-241.
French, J. R. J. 1994. Combining physical barriers, bait and dust toxicants in future strategies for subterranean termite control Martin, M. M. 1979. Biochemical implications of insect mycophagy. Biological Reviews 54: 1-21.
Waller, D. A. 1996. Ampicillin, tetracycline and urea as protozoicides for symbionts of Reticulitermes flavipes and R. virginicus (Isoptera: Rhinotermitidae). Bull. Entomol. Res. 86: 77-81.
Waller, D. A., J. P. La Fage, Gilbertson, and M. Blackwell. 1987. Wood decay fungi associated with subterranean termites in southern Louisiana. Proc. Entomol. Soc. Wash. 89: 417-424.
Proceedings of the 3rd International Conference on Urban Pests.
Wm H. Robinson, F. Rettich and G.W. Rambo (editors). 1999.

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