Scientists are continually testing new compounds in a bid to find a chemical with termite repellent properties. Here, we outline the latest developments in this field.
Latest termite repellents research
New materials with termite activity
Chemicals and materials that repel termites, instead of or in addition to killing termites, are a focus of research and evaluation.
Researchers in the US have taken a closer look at menadione (vitamin K3), which is known to have toxic effects on some insects, although its impact on termites is unknown. It is of particular interest due to its low mammalian toxicity. Working on Coptotermes formosanus, the researchers evaluated the effects of menadione on foraging behaviour and mortality.1
In comparison to fipronil, menadione delivered lower mortality at the same concentration (0.6 μg/μL), but was just as effective in reducing feeding (filter paper consumption). However, in no-choice trials menadione delivered comparable levels of mortality. The researchers concluded that although menadione does deliver mortality at low concentration levels (with a mode of action similar to chlorfenapyr), it is its repellent properties that are likely to provide more potential benefit in termite management. So rather than investigating its potential as a soil treatment, further trials should look at its use in wood preservation and potentially in the direct treatment of termites in active infestations.
Biochar (pictured above) has received a lot of attention as a result of its potential to mitigate greenhouse gas emissions. Burning and natural decomposition of trees and agricultural matter releases large amounts of carbon dioxide into the atmosphere. If the same materials undergo a slow pyrolysis process (heating in the absence of oxygen), a carbon-rich charcoal (biochar) is produced. This can sequester the carbon for up to 5000 years. As such, the potential uses of biochar are being investigated for soil improvement and fertility. As a consequence, it is being evaluated for its impact on soil arthropods. A recent study investigated its impact on Coptotermes formosanus.2
The study demonstrated that concentrations of biochar in the soil of >5% repelled the termites and started to impact their survival. At these levels, the soil pH increased and the soil moisture decreased. In addition, when higher levels of biochar were added (>20%) the soil bacteria composition was altered and the abundance of pathogens deleterious to termites also increased. The researchers concluded that soil that has been altered to include biochar at levels of >10% has the potential for use in termite management and should be investigated further.
References
1 Ngo, Kieu & Castillo, Paula & Laine, Roger A & Sun, Qian. (2021). Effects of Menadione on Survival, Feeding, and Tunneling Activity of the Formosan Subterranean Termite. Insects. 12. 1109. 10.3390/ insects12121109.
2 Chen, Yong & Zhao, Chongwen & Zhang, Dandan & Zhang, Shijun & Zeng, Wenhui & Li, Zhi-Qiang. (2022). The effect of amending soils with biochar on the microhabitat preferences of Coptotermes formosanus (Blattodea: Rhinotermitidae). Ecotoxicology and Environmental Safety. 232. 113240. 10.1016/j.ecoenv.2022.113240.
