## 3 Results
### Effects of the Combined Treatment  
In _D. suzukii_ exposed to combined PH\({}_{3}\) fumigation and cold-temperature treatment (1 \({}^{\circ}\)C and 5 \({}^{\circ}\)C), mortality in all developmental stages except the adult stage was observed (Figure 2). Between the two combined treatment methods, fumigation after cold-temperature treatment showed a stronger insecticidal effect on eggs, with a statistically significant difference. However, cold-temperature treatment after fumigation showed similar insecticidal effect, regardless of the temperature. Compared with fumigation alone, the combined treatment showed synergistic effects in the larval and pupal stages, but there was no statistically significant difference between the treatment methods or temperatures.  
The fumigation LCT values for the effective control of _D. suzukii_ exposed to the combination treatment were calculated using the pupal stage LCT value because pupae had the highest tolerance to PH\({}_{3}\) (Table 2). There was no significant difference in the SR value of PH\({}_{3}\) among room temperature (control) and cold temperatures (1 \({}^{\circ}\)C and 5 \({}^{\circ}\)C) in the combined treatment groups. However, the LCT\({}_{99}\) value of PH\({}_{3}\) combined with 1 \({}^{\circ}\)C treatment was 4.59 times higher than the LCT\({}_{99}\) value of PH\({}_{3}\) of the control.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Stage** & \(n\) & \begin{tabular}{c} **LCT\({}_{50}\)****(mg:h/L)** \\ **(95\% CL****^)** \\ \end{tabular} & **TR****\({}^{\circ}\)** & \begin{tabular}{c} **LCT\({}_{99}\) (mg-h/L)** \\ **(95\% CL)** \\ \end{tabular} & **TR****\({}^{\circ}\)** & **Slope** \(\pm\) **SE** & _df_ & \(\mathbf{x^{2}}\) \\ \hline Egg & 360 & \begin{tabular}{c} 0.41 \\ (0.37–0.44) \\ \end{tabular} & 8.91 & \begin{tabular}{c} 1.76 \\ (1.39–2.48) \\ \end{tabular} & 20 & 3.64 \(\pm\) 0.36 & 2 & 104.87 \\ \hline L larva & 450 & \begin{tabular}{c} 0.33 \\ (0.31–0.35) \\ \end{tabular} & 7.17 & \begin{tabular}{c} 1.14 \\ (0.97–1.4) \\ \end{tabular} & 12.95 & 4.34 \(\pm\) 0.32 & 3 & 162.88 \\ \hline Pupa & 720 & \begin{tabular}{c} 4.32 \\ (3.90–4.77) \\ \end{tabular} & 93.91 & \begin{tabular}{c} 53.20 \\ (37.11–87.48) \\ \end{tabular} & 604.55 & 2.13\(\pm\) 0.18 & 6 & 142.16 \\ \hline Adult & 378 & \
\begin{tabular}{c} 0.046 \\ (0.044–0.048) \\ \end{tabular} & 1 &
\begin{tabular}{c} 0.088 \\ (0.081–0.100) \\ \end{tabular} & 1 & 8.22 \(\pm\) 0.68 & 3 & 145.08 \\ \hline \hline \end{tabular}  
* LCT\({}_{50}\) and _99_; 50% and 99% lethal concentration time. \({}^{\circ}\) Confidence limit. \({}^{\circ}\) TR (Tolerance ratio) = LCT value of each developmental stages/LCT value of _D. suzukii_ adult.  
\end{table}
Table 1: Fumigation effect of PH\({}_{3}\) against all _D. suzukii_ developmental stages in a 12 L desiccator after 4 h of exposure at 20 \({}^{\circ}\)C.  
A scale-up experiment was performed in a 0.65 m\({}^{3}\) fumigation chamber considering the LCT\({}_{99}\) value in pupae exposed to the combined treatment at 1 \({}^{\circ}\)C because pupae had the highest tolerance in the experiment in the 12 L desiccator (Table 3). A mortality of 100% was observed in all _D. suzukii_ developmental stages, regardless of insect position at the top, middle, or bottom of the fumigation chamber.