# Repellency of Veratraldehyde (3,4-Dimethoxy Benzaldehyde) against Mosquito Females and Tick Nymphs
## 3 Results
### Determination of the Effective Dose of Veratraldehyde  
To determine the effective dose of veratraldehyde contained in a formulation, four doses (5, 7, 10 and 15%) of veratraldehyde in ethanol solution were prepared, and their repellency against mosquito females was compared to that of 20% DEET using the arm-in-cage test. Veratraldehyde showed 83 and 76% repellency against _A. albopictus_ females for 3 and 4 h, respectively (Table 3). In a test using a 7% solution, veratraldehyde showed 88 and 77% repellency for 5 and 6 h after treatment, respectively, and 10 and 15% solutions exhibited \(\geq\)96% repellent activity against _A. albopictus_ females for 6 h. Although the repellency of the four veratraldehyde solutions was strong, 20% DEET maintained 99% repellency for 6 h. In addition, veratraldehyde solutions kept CPTs of 1.3-5.3 h, and 10% veratraldehyde showed the same CPT (5.3 h) compared to that of 20% DEET against _A. albopictus_ (Table 3). Veratraldehyde showed 100% repellency against C. _pipiens_ females for 3 h at all the tested doses, indicating that its repellency against _C. pipiens_ was higher than that against _Aedes_ (Table 4). In a test 6 h after treatment, veratraldehyde showed 84, 83, 100 and 88% repellency at concentrations of 5, 7, 10 and 15%, respectively, and the activity was comparable to the 95% repellency observed for 20% DEET. The tested veratraldehyde solutions maintained CPTs 4.7-6 h, and the CPT of the 10% solution was comparable to that of 20% DEET (Table 4). Based on the results for the four veratraldehyde solutions, the effective dose of veratraldehyde was determined to be 10%. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{
\begin{tabular}{c} **Conc.** \\ **(mg/cm\({}^{2}\))** \\ \end{tabular} } & \multicolumn{4}{c}{**Repellency (\%, Mean \(\pm\) SB \({}^{\star}\)**} \\ \cline{3-6}  & **1 h** & **2 h** & **3 h** & **4 h** & **5 h** \\ \hline \multirow{4}{*}{Veratraldehyde} & 0.09 & \(100\pm 0\)a & \(100\pm 0\)a & \(100\pm 0\)a & \(85\pm 2.9\)b & \(75\pm 5.0\)ab \\  & 0.05 & \(100\pm 0\)a & \(98\pm 2.5\)a & \(93\pm 4.8\)a & \(88\pm 2.5\)b & \(78\pm 4.8\)a \\  & 0.02 & \(98\pm 2.5\)ab & \(98\pm 2.5\)a & \(95\pm 5.0\)a & \(83\pm 2.5\)bc & \(60\pm 5.8\)c \\  & 0.01 & \(98\pm 2.5\)ab & \(90\pm 5.8\)ab & \(95\pm 2.9\)a & \(65\pm 2.9\)c & \(48\pm 4.8\)abc \\ \hline \multirow{4}{*}{DEET} & 0.09 & \(100\pm 0\)a & \(98\pm 2.5\)a & \(100\pm 0\)a & \(100\pm 0\)a & \(50\pm 4.1\)bc \\  & 0.05 & \(100\pm 0\)a & \(98\pm 2.5\)a & \(88\pm 2.5\)a & \(85\pm 2.9\)b & \(70\pm 4.1\)abc \\ \cline{1-1}  & 0.02 & \(98\pm 2.5\)ab & \(78\pm 2.5\)bc & \(50\pm 4.1\)b & \(25\pm 2.9\)d & \(20\pm 4.1\)d \\ \cline{1-1}  & 0.01 & \(88\pm 4.8\)b & \(60\pm 4.1\)c & \(50\pm 7.1\)b & \(30\pm 7.1\)d & \(23\pm 4.8\)d \\ \hline \hline \end{tabular}  
* Means with the same letter are not significantly different according to a Bonferroni multiple-comparison test (\(p=0.05\)).  
\end{table} 
Table 2: The repellent activity of veratraldehyde against _Haemaphysalis longicornis_ nymphs using the filter paper assay.