Subterranean termite biology and control

A single colony of subterranean termites can contain millions of workers foraging throughout an area that can span a hundred meters or more (Su and Scheffrahn, 1998) Hidden nesting and feeding habits, large foraging areas (Husseneder et al., 2005b; Messenger et al ., 2005), high reproduction rates in mature colonies (Su and Scheffrahn, 1987), and the potential of nymphs and workers to become reproductives when the previous generation of kings and queens is declining (Thorne et al ., 1999; Vargo et al ., 2003, 2006a, 2006b; Hus-seneder et al , 2005b, 2007) make subterranean termite control challenging To eliminate an entire colony, it is necessary to kill not only the foraging population but also the reproductives in an efficient manner

Traditional treatment for termites relies on soil or spot treatments with pesticides (Su and Scheffrahn, 1998) . These chemical control methods pose certain risks of environmental contamination, nontarget effects, and the development of insecticide resistance The need for reduction of chemical residuals in the environment has required that newly developed pesticides be biodegradable, and thus, their efficacies rapidly decrease (Su and Scheffrahn, 1998) Therefore, the public increasingly demands termite control technology that is not only environmentally friendly and target specific, but also sustainable long enough to effectively eliminate entire termite colonies

One of the most successful reduced-risk approaches to termite control is the targeted bait approach using slow-acting toxicants, such as insect growth regulators (Su and Schef-frahn, 1998) Foraging workers consume the bait toxicant and transfer the active ingredient through the colony via social interactions, such as food exchange and grooming Because the concentration of toxicant is diluted as it is passed among nest mates, a large number of foragers must consume sufficient amounts of bait toxicant to achieve successful colony elimination . Although the concentration of toxicant in the bait can be adjusted (Su and Scheffrahn, 1998), the uptake of sufficient amount of toxicant cannot be guaranteed because subterranean termites do not necessarily have stable foraging areas and may (in some cases) move frequently in and out of bait stations or abandon bait stations after disturbance (Aluko and Husseneder, 2007)

Theoretically, the efficacy of baiting systems could be further improved by employing live biological control agents, such as nematodes, viruses, fungi, and bacteria (Su and Scheffrahn, 1998; Culliney and Grace, 2000) . Because the active ingredient in the bait would be live organisms, the agents in theory would be self-sustaining, self-replicating, and self-perpetuating within the colony Although there is evidence that some entomopathogens kill insects in laboratory studies, most of them have largely failed to meet expectations in field trials (reviewed in Su and Scheffrahn, 1998; Culliney and Grace, 2000). In termites, the effectiveness of biocontrol agents is limited due to biological constraints and logistical problems of their application to social insects For example, termites have few natural pathogens and their pathogenicity is weak (Culliney and Grace, 2000) . Usually, pathogens are not persistent in the environment of the termite colony because termites employ "hygienic" measures such as fumigating their nests with naphthalene to kill pathogens (Chen et al , 1998) Termites have the ability to avoid contact with pathogens, remove pathogens through grooming, and isolate infected individuals from the colony (Logan et al., 1990; Culliney and Grace, 2000). Termites also have an efficient immune system to eliminate infections with foreign pathogenic microbes (Rosengaus et al ., 1999) . It has been suggested that even the gut community protects termites against opportunistic invaders and pathogens (Veivers et al , 1982) Overcoming defensive mechanisms and delivering pathogens throughout an entire colony would require a large number of initially infected individuals and a high dose of inoculum, which is difficult to achieve Mass production and reapplications of foreign pathogens required to achieve colony control would be expensive, time and labor intensive, and not necessarily justified by the poor performance, limitation of treatment to the immediate area of application, and the temporary treatment effects (Grace, 1997; Culliney and Grace, 2000) In summary, there is a need for developing more effective termite control techniques against subterranean termites

Oplan Termites

Oplan Termites

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