## 3 Results and Discussion
### Commercial-Scale Trials and Effects of EF Treatment on Quality  
#### 3.2.1 Rubber Trees  
Complete control of _R. speratus_ workers was achieved in the commercial scale trials (7.2 m\({}^{3}\)) with 35 g/m\({}^{3}\) of EF held for 4 h at 15 \(\pm\) 1 \({}^{\circ}\)C with a 9% loading ratio (\(w/v\)) on two species of potted rubber plants. The Ct product of EF was 84.70 \(\pm\) 0.5 g h/m\({}^{3}\), which was greater than the EF LC\({}_{99\%}\) value for _R. speratus_ at >15 \({}^{\circ}\)C (LC\({}_{99\%}\) = 77.24 g h/m\({}^{3}\)) [9]. Using the liquid EF vaporizer and nitrogen gas as propellent appeared to effectively deliver EF gas into the fumigation tent. The concentrations of EF were evenly distributed among three different parts inside the fumigation tent (Table 1). Quality assessment conducted 30 d post fumigation treatment showed that there were no significant differences in leaf chlorophyll contents, leaf hue values, or overall plant injury (i.e., dropped leaves or leaf browning/curling/shriveling) between the EF-treated and untreated rubber plants (Table 2). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Applied Dose (g/m\({}^{3}\))** & \begin{tabular}{c} **EF Sampling** \\ **Location Inside Tent** \\ \end{tabular} & **Ct Products (g h/m\({}^{3}\))** & \begin{tabular}{c} **No. of R. _spertatus_** \\ **Workers Tested** \\ \end{tabular} & \
\begin{tabular}{c} **No. of R. _spertatus_** \\ **Workers Dead** \\ \end{tabular} &
\begin{tabular}{c} **Mortality of R.** \\ _spertatus Workers (\%)_ \\ \end{tabular} \\ \hline Untreated control & - & - & 720 & 0 & 0 \\ Front & 85.8 & 899 & 899 & 100 \\
35 & Middle & 83.9 & 741 & 741 & 100 \\ Rear & 84.4 & 750 & 750 & 100 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Concentration \(\times\) time (Ct) products (g h/m\({}^{3}\)) of and the mortality of _Reticulitermes spertatus_ workers from 35 g/m\({}^{3}\) EF fumigation at 15 \(\pm\) 1 \({}^{\circ}\)C for 4 h treated on imported potted rubber plants (_Fiscus retusa_ and _F. benghalensis_) in commercial-scale fumigation trials conducted in a 7.2 m\({}^{3}\) PVC-trapulain tent. Figure 2: Concentration loss of ethyl formate (EF) (C/C\({}_{0}\)) in 6.8 L glass fumigation chamber with 70% loading ratio (\(w/v\)) of imported marble. EF was treated at 35, 53, and 70 g/m\({}^{3}\) for 4 h at 15 \({}^{\circ}\)C C = EF concentration determined at one of the time intervals and C\({}_{0}\) = EF concentration at 0.1 h. EF concentration was determined at 0.1, 1.0, 2.0, and 4.0 h after EF had been applied to the fumigation chamber. Previous studies have shown that EF was an effective fumigant for other imported nursery products such as bare-rooted seedlings and potted nursery plants [31]. For example, [PERSON] et al. showed that EF treatment at 30 g/m\({}^{3}\) for 4 h at \(>\)16 \({}^{\circ}\)C was effective at controlling _Pseudococcus longsipinus_ and _P. orchidicola_ infesting _Pachira macrocapa_ or _Syngonium podophyllum_ plants [31]. As for the imported potted rubber plants in this study, the imported bare-rooted nursery plants also required an extended growth period after fumigation to increase their commercial value. They reported that there were no differences in various measures of quality for nursery plants grown from bare-rooted plants with or without EF treatment [31]. Thus, EF treatment appears to be a viable MB alternative treatment option for these types of imported nursery products, both in terms of efficacy on the target pests and lack of phytotoxicity. EF is not free of risk of phytotoxicity, and its phytotoxicity on fresh produce or plants appears to depend on the used EF dose (i.e., the higher the dose is, the more the damage), or the treated plant species or variety [31]. In the study, at the tested EF dose, there was no leaf drop, obvious leaf damage, or plant die back after EF treatment.