Colony Size Affects the Efficacy of Bait Containing Chlorfluazuron Against the Fungus-Growing Termite <I>Macrotermes gilvus</I> (Blattodea: Termitidae)

Abstract

The efficacy of chitin synthesis inhibitors (CSIs) against fungus-growing termites is known to vary. In this study, 0.1% chlorfluazuron (CFZ) cellulose bait was tested against medium and large field colonies of Macrotermes gilvus (Hagen). The termite mounds were dissected to determine the health of the colony. Individual termites (i.e., workers and larvae) and fungus combs were subjected to gas chromatography-mass spectrometry (GC-MS) analysis to detect the presence of CFZ. In this study, 540.0 ± 25.8 g (or equivalent to 540.0 ± 25.8 mg active ingredient) and 680.0 ± 49.0 g (680.0 ± 49.0 mg active ingredient) of bait matrix were removed by the medium- and large-sized colonies, respectively, after baiting. All treated medium-sized colonies were moribund. The dead termites were scattered in the mound, larvae were absent, population size had decreased by 90%, and the queens appeared unhealthy. In contrast, no or limited effects were found in large-sized colonies. Only trace amounts of CFZ were detected in workers, larvae, and fungus combs, and the population of large-sized colonies had declined by only up to 40%. This might be owing to the presence of large amount of basidiomycete fungus and a drastic decrease of CFZ content per unit fungus comb (a main food source of larvae) in the large-sized colonies, and hence reduced the toxic effect and longer time is required to accumulate the lethal dose in larvae. Nevertheless, we do not deny the possibility of CSI bait eliminating or suppressing the higher termite if the test colonies could pick up adequate lethal dose by installing more bait stations and prolonging the baiting period.

Evaluation of fipronil and imidacloprid as bait active ingredients against fungus-growing termites (Blattodea: Termitidae: Macrotermitinae)

“…Usually workers of rhinotermitid species (and some termitids in other sub-families) moult many times, hence they are more vulnerable to chitin synthesis inhibitors (Roisin, 2000). However, as there is a single instar in the worker caste in the sub-family Macrotermitinae (Neoh & Lee, 2009), they are less vulnerable to chitin synthesis inhibitors (Lee et al, 2007(Lee et al, , 2014Neoh et al, 2011). The 'larvae' (youngest instars without gut flora) are vulnerable in Macrotermes gilvus (Hagen), because they moult several times, however as larvae are a relatively small proportion of the colony, elimination rarely occurs (Neoh et al, 2011;Lee et al, 2014).…”

“…However, as there is a single instar in the worker caste in the sub-family Macrotermitinae (Neoh & Lee, 2009), they are less vulnerable to chitin synthesis inhibitors (Lee et al, 2007(Lee et al, , 2014Neoh et al, 2011). The 'larvae' (youngest instars without gut flora) are vulnerable in Macrotermes gilvus (Hagen), because they moult several times, however as larvae are a relatively small proportion of the colony, elimination rarely occurs (Neoh et al, 2011;Lee et al, 2014). Conditions for high levels of colony suppression include: many larvae, small colony size, and long baiting periods, none of which can be predicted (Dhang, 2011;Lee et al, 2014).…”

Naturalization and Control ofCoptotermes gestroi(Blattodea: Rhinotermitidae) in a Taiwanese Forest

“…eliminated, many higher termite genera including Odontotermes, Microtermes, Macrotermes, Microcerotermes, and Globitermes was discovered at the bait stations; however, the baits were generally ineffective in controlling these higher termites. The baits with chitin synthesis inhibitors could suppress small colonies of fungus-growing termites, but they were ineffective in controlling large colonies (Lee et al 2014). Although termite baits were consumed by O. formosanus, the bait is not likely to eliminate its colony, which limits the negative effect of termite bait on nontarget termite species.…”

Efficacy of Minimum Application of Chlorfluazuron Baiting to Control Urban Subterranean Termite Populations of Coptotermes gestroi (Wasmann) (Blattodea: Rhinotermitidae)

“…Furthermore, chemical controls are the most common method used against pests of urban forests in Malaysia [ 5 ], for example, trees infested by C. gestroi and Coptotermes curvignathus are usually treated with an insecticide such as chlorpyrifos, fipronil, or imidacloprid [ 6 ]. However, as Lee et al (2014) noted, the baiting system has emerged as a popular option for controlling subterranean termites [ 6 ]. The effectiveness of baiting depends on the foraging of the termites to encounter the bait, feed on the bait, and the horizontal transfer of residual insecticide deposits between nestmates [ 7 ].…”