LABORATORY AND FIELD METHODS FOR INVESTIGATING SUBTERRANEAN TERMITE CONTROL

Abstract:
Determining termiticide performance has, historically, been conducted by assessing attack of wooden boards placed over treated soil. This method was developed by the USDA-FS Gulfport laboratory, and is referred to as the ground-board test. A modification of this involves pouring concrete over the treated soil to simulate a sub-slab treatment. Both tests are performed in 4 states and provide the basis of the data required for EPA registration which may, in turn, contribute to registration in other countries. Several modifications of the ground board and concrete slab methods have been developed as increasing attention has been paid to the influence of factors such as soil type upon degradation rates, with the withdrawal of the persistent organochlorine soil termiticides such as chlordane. Vertical concrete square structures, centred in trenches, have been used that allow soil samples to be taken for the determination of residues in addition to the observable attack of termites on pine boards. Similarly, the termiticide may be mixed with soil, then either covered or left exposed for various periods before soil cores are removed for chemical analysis and bioassay. By using sites with different soil characteristics, it is possible to establish a comprehensive picture to help interpret termiticide performance, when used in the """"traditional"""" pre- and post-construction barrier applications, and in less widely used applications such as direct injection into masonry, as occurs in France, for example. The main laboratory tests that are used to evaluate the repellent and contact activity of termiticides feature the inclusion of a portion of treated soil in test apparatus where termites have the choice of tunnelling through that soil to a food source, or remaining in another part of the apparatus where food and moisture are present. Some of the more recently developed methods are aimed at examining alternative termite control methods, which require more subtle means of evaluation. Bait toxicants, or trap-treatrelease systems require the use of markers or dyes to help estimate colony size and foraging behaviour. They have also required the development of laboratory systems that incorporate colony behaviours so that the potential to transfer dose via trophallaxis or grooming has been determined for slow-acting compounds with different modes of action.