SUBTERRANEAN TERMITE CONTROL SYSTEM
C.D. MAMPE, PhD.
Baits to control subterranean termites have been considered since the early 1960's. However, the efficacy of chlordane and related soil termiticides, their availability and low cost and the lack of suitable toxicants for baits stifled development for several decades.
With the loss of chlordane and related compounds and the heightened awareness of environmental concerns, interest in termite baits was renewed. Currently, there are three commercial systems available: Dow AgroScience's "Sentricon", FMC's "FirstLine" and Ensystex's "Exterra". The FirstLine system employs a slow-acting toxicant (sulfluramide) while the other two systems employ growth regulators (hexaflumeron and diflubenzuron, respectively). Both Dow AgroScience and Enystex claim "colony elimination" while FMC claims "colony suppression".
All of the above three systems utilize in-ground monitors and, once termites locate the monitors, the toxicant is installed in the station.
A new system has been developed by Gordon Laboratories and distributed by HomeGuard Distributors, Inc. It also consists of monitors but rather than a pesticide employed for control, predacious mites group are introduced to control termites. This study evaluates twelve residential buildings treated with the HomeGuard system.
Material and Methods:
Eleven houses were located in Pinellas County and one in Pasco County, Florida, which had active subterranean termite infestations in 1998. The owners agreed to have the HomeGuard system installed without any soil treatments of termiticide. Each house was graphed and the site(s) of termite infestation noted. All twelve houses were supported slab construction.
The HomeGuard monitors were installed using a battery powered drill and a soil auger.
Holes approximately 3 inches in diameter and 6 inches deep were drilled approximately every 10 linear feet around each structure. The holes were approximately 24 to 36 inches from the foundations to ensure that the monitors would not be placed in soil previously treated for termites although the houses selected had no known history of any previous treatments.
The HomeGuard monitors are three inches in diameter and 6-1/2 inches long. They have a corrugated cardboard matrix. The tops are clear to permit visual inspections and to enhance soil moisture condensation. The monitors are inserted into the soil so that the tops are slightly above grade. Six to eight ounces of distilled water is poured into the matrix before installation.
The monitors were inspected monthly to determine if termites had tubed through the cardboard matrix up to the underside of the station top. When this occurred, the active station was switched with an adjacent inactive station. When two or more stations became active, mites were introduced by replacing active stations with new stations containing the cardboard matrix which had been inoculated with mite eggs. Termite soldiers were also collected for identification.
If the mite-laden matrix became significantly consumed, it was replaced with another matrix inoculated with mite eggs.
Monitors were inspected every month until all activity ceased at the property in question. At that time, inspections were made quarterly. If new activity was noted, the matrix was
again replaced with matrix inoculated with mite eggs and inspections resumed on a monthly basis.
The interior and exterior of each house was inspected periodically for evidence of active infestation.
A summary of the results is shown in Table 1. The properties were in the study for 13 to 53 months. Four properties (Nos. 2, 4, 5 and 11) dropped out of the project for various reasons. Property #2 was sold, the owner of property #4 had financial problems and properties #5 and 11 cancelled because no termite activity was noted for a period of time after the mites were introduced. Note that months with nothing recorded were months when no inspection was made of the property in question.
No evidence of termite activity was ever noted in or on a structure following the first month of installing mites.
Table 1. Summary of termite activity at twelve properties in Florida treated with the HomeGuard Subterranean Termite Control System .
NA = No activity
(X)B = No. of stations with activity and/or baited with mites
C = Account canceled
MNA = Longest number of months without activity
Comments and Conclusions:
All initial termite infestations were identified as Reticultermes flavipes. In the case of Properties #1 and 2, termites collected in stations at months 28 and 33 respectively were identified as R. virginicus. This indicates in these two properties that new activity was due to a colony different than the original. In sites 3 ,8, 10 and 12, it is unknown if renewed activity was due to the original colony recovering or new colonies moving into the area. However, the new "hits" on monitors at property #12 were located in an area different from the original activity which suggests a different colony.
None of the properties showed any termite activity in or on the structures one month following introduction of mites into the system. Activity or lack thereof in or on the structures served as a control. The system does eliminate termite activity to prevent further activity and damage in a structure.
Whether or not the system eliminated any colony can be debated. Su and Scheffrahn (1996) originally used criteria of no activity for two consecutive months following acceptance of bait. The Ensystex system used six consecutive months of no activity following baiting (Exterra Termite Interception and Baiting System at http://www.ensystex.com/faqs.html#anchor74716). Using the Su and Scheffrahn criteria, colonies were eliminated at every property. Using the Ensystex criteria of six months of no activity, all twelve properties had the colonies eliminated. This test is considered more rigorous than the Sentricon and Ensystex tests as the HomeGuard monitors actually attract termites.
The data also show that continued monitoring and, when necessary, introducing a control agent, is necessary to continue to protect a structure from termite attack. Whether new colonies move in or existing colonies recover, structures sustain continuing termite pressure. If the monitoring system is removed, some termite populations may locate the structure and reinfestation may occur.
Su, N.Y. & R.H. Scheffrahn. 1996. A review of the evaluation criteria for bait-toxicant efficacy against filed colonies of subterranean termites. Sociobiology 28:521-530.
Respectively submitted by:
C. D. Mampe 8/02/02
C.D. Mampe, PhD. Date
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