Colony Suppression and Possible Colony Elimination of the Subterranean Termites Coptotermes formosanus and Reticulitermes speratus by Discontinuous Soil Treatment Using a Diluent of Fipronil Suspension Concentrate

Termite baiting-how it changed the landscape of the pest management industry and termite research in Southeast Asia

The management of subterranean termite pests remains a major challenge in Southeast Asia, where these pests cause significant structural and economic damage. Termite baiting has emerged as an effective option to conventional soil termiticides, offering a safer pest management approach with reduced chemical input into the environment. In this paper, we review the history of termite research in Southeast Asia, highlighting the turning points of termite research, from agriculture and plantations to buildings and structures, and the transformative impact of termite baiting on the pest management industry in the region over the last 25 yr. We also discuss the outcome of a survey of pest management professionals on their baiting practices, bait performance, and reinfestation rates. All bait products eliminated termite colonies. There were significant differences in terms of the baiting period to colony elimination, with Xterm outperforming Sentricon, Exterra, and Exterminex. Above-ground (AG) baiting was preferred over in-ground (IG) baiting due to construction constraints and low IG station interception rates. While bait effectively controlled Coptotermes spp., challenges persist in managing fungus-growing termites such as Macrotermes gilvus Hagen. Reinfestation occurred in < 10% of baited premises.

Ethyl 2,4-dioxovalerate triggers aggregation and tunneling preference of Formosan subterranean termites (Blattodea: Rhinotermitidae) and enhances the effectiveness of fipronil

Our previous study shows that Coptotermes formosanus (Blattodea: Rhinotermitidae) preferred to stay on filter paper treated with ethyl 2,4-dioxovalerate, a metabolite in the soil fungus Trichoderma virens. Here, we hypothesized that adding ethyl 2,4-dioxovalerate in sand could trigger aggregation and tunneling preferences of C. formosanus and improve the effectiveness of liquid termiticide. In aggregation-choice tests, significantly more termites were found on/in sand blocks containing ethyl 2,4-dioxovalerate (250 µg/g) than untreated blocks throughout the 24-h experiments. In the tunneling-choice tests, termites also excavated significantly more tunnels in the sand treated with ethyl 2,4-dioxovalerate (2.5, 25, or 250 µg/g) than untreated sand. However, in no-choice tests, ethyl 2,4-dioxovalerate (2.5, 25, or 250 µg/g) did not significantly affect tunneling activities, termite survival, wood consumption, or activities of detoxification enzymes (peroxidase, superoxide dismutase, and catalase) compared to controls. Interestingly, in aggregation- and tunneling-choice tests, termites preferred to stay and made more tunnels in sand treated with both ethyl 2,4-dioxovalerate (250 µg/g) and fipronil (1 µg/g) than untreated sand. In addition, in choice tests, sand treated with the combination of ethyl 2,4-dioxovalerate (250 µg/g) and fipronil (1 µg/g) caused significantly higher termite mortality than the sand treated with only fipronil (1 µg/g). Our study showed that ethyl 2,4-dioxovalerate may enhance the effectiveness of fipronil (1 µg/g in sand) by triggering aggregation and tunneling preferences of termites, thereby increasing the contact between termites and fipronil.

Death zone minimizes the impact of fipronil-treated soils on subterranean termite colonies by negating transfer effects

The use of nonrepellent liquid termiticides against subterranean termites has long relied on the assumption that foraging termites in soils could transfer toxicants to nestmates to achieve population control. However, their dose-dependent lethal time can lead to rapid termite mortality in proximity of the treatment, triggering secondary repellency. The current study characterizes the dynamic nature of the "death zone," i.e., the area adjacent to soil termiticides that termites would avoid owing the accumulation of cadavers. Using whole subterranean termite laboratory colonies of Coptotermes gestroi (Wasmann) with 3 × 15 m foraging distances, fipronil was implemented at 1.5 m, 7.5 m, or 12.5 m away from colony central nests, emulating a corrective action against an termite structural infestation. For treatments at 7.5 m and 12.5 m, the death zone stabilized at an average of ~2.56 m away from the treatment after 40 d post-treatment, and colonies suffered as little as 1.5% mortality by 200 d post-treatment. Colonies located 1.5 m away from the treatment minimized the death zone to ~1.1 m and suffered as little as 23.5% mortality. Mortality only occurred within the first few days of treatment from initial exposure, as the rapid emergence of the death zone negated further transfer effects among nestmates over time. In some cases, foraging termites were trapped within the infested structure. While technically nonrepellent, fipronil becomes functionally repellent from the rapid mortality onset near the treatment. Even if diligently implemented to successfully protect structures, surrounding termite colonies are minimally impacted by fipronil soil treatments.

Effects of Menadione on Survival, Feeding, and Tunneling Activity of the Formosan Subterranean Termite

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a highly destructive pest and a cosmopolitan invasive species. Sustainable termite management methods have been improving with the search for novel insecticides that are effective, safe, and cost efficient. Menadione, also known as vitamin K₃, is a synthetic analogue and biosynthetic precursor of vitamin K with low mammalian toxicity. Menadione has shown insecticidal activity in several insects, presumably due to interference with mitochondrial oxidative phosphorylation. However, little is known about its effectiveness against termites. In this study, we evaluated the toxicity and repellency of menadione in C. formosanus. Our results showed that menadione affected the survival and feeding activity of termites both in filter paper and substrate (sand) treatments, and menadione influenced termite tunneling activity in treated sand. In a no-choice assay, ≥90% mortality after seven days and minimal or no food consumption were recorded when sand was treated with menadione at 6 to 600 ppm. In a two-choice assay with a combination of treated and untreated sand, termites were deterred by menadione at 6 to 600 ppm and exhibited low mortality (≤30%) over seven days, while tunneling activity was prevented with 60 to 600 ppm of menadione treatment. Overall, our study demonstrated dose-dependent toxicity and repellency of menadione in C. formosanus. The potential use of menadione as an alternative termite control agent is discussed.