# A natural barrier: tick‐repellent potential of a spruce‐derived volatile blend against Hyalomma excavatum and Ixodes ricinus

## TL;DR

This study shows that spruce-derived volatile blends are effective at repelling two common tick species better than existing commercial repellents.

## Contribution

The study introduces two novel plant-derived volatile blends that show superior tick repellent efficacy compared to commercial products.

## Key findings

- Blends 3 and 4 repelled both Hyalomma excavatum and Ixodes ricinus ticks more effectively than DEET and other commercial repellents.
- The plant-derived blends demonstrated broad-spectrum repellent activity across different tick life strategies.
- The blends offer potential for integrated vector management due to their dual efficacy against ticks and mosquitoes.

## Abstract

Ixodes ricinus and Hyalomma excavatum are two widely dispersed vectors of pathogens, including those that cause Lyme disease and Crimean–Congo haemorrhagic fever in the human population. Recently developed, plant‐derived, mosquito‐repellent blends have shown promise against other vector clades, and this study assesses these blends as potential tick repellents. Blends of (+)‐borneol, bornyl acetate, eugenol, isoeugenol and camphor were assessed in two formats: blends 3 and 4. Ticks were assessed using the moving object bioassay (Ixodes) or a dual‐choice behavioural assay (Hyalomma). Both blends were compared against negative controls and four commercially available synthetic repellents: N,N‐diethyl‐3‐methylbenzamide (DEET), 2‐(2‐hydroxyethyl)‐1‐methylpropylstyrene 1‐piperidine carboxylate) (Picaridin), 3‐(N‐n‐butyl‐N‐acetyl)‐amino‐propionic acid ethyl ester (IR3535) and p‐menthane‐3,8‐diol (PMD). Results demonstrate the efficacies of blends 3 and 4; moreover, both were more effective than the commercial repellents (P < 0.05). Blend 3 was marginally more effective than blend 4, and differences in the repellent action were noted for each of the tick species, suggesting broad‐spectrum vector‐repellent activities, irrespective of life strategy. Overall, this work demonstrates the clear potential of blends 3 and 4 as tick repellents that offer an improved vector response over currently available commercial repellents. Furthermore, that the same repellent blends are capable of tick repellency in addition to mosquito repellency, offers the potential for widely dispersed usage across a range of integrated vector management strategies. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Both active and passive questing ticks, Hyalomma excavatum and Ixodes ricinus, were assessed for behavioural responses to two novel plant‐derived repellent volatile organic compound blends. Both tick species were repelled by the products, and both novo blends were significantly more repellent than currently available commercial products.