## 3 Results and Discussion
### Commercial-Scale Trials and Effects of EF Treatment on Quality
#### 3.2.2 Stone Products  
Complete control of _R. speratus_ workers was also achieved in the commercial-scale trials (33.6 m\({}^{3}\)) with 35 g/m\({}^{3}\) EF held for 4 h at 15 \(\pm\) 2 \({}^{\circ}\)C with a 60% loading ratio (\(v/v\)) of imported marble (2 pieces, 10.5 m\({}^{3}\)/piece). This was expected, as the Ct product of EF from the marble fumigation trial was 263.58 \(\pm\) 10.9 g h/m\({}^{3}\), which was much higher than the 77.24 g h/m\({}^{3}\) necessary for 99% mortality of _R. speratus_ at \(>\)15 \({}^{\circ}\)C [9]. As in our rubber plant fumigation trials, the concentrations of EF in three different parts inside the fumigation tent were uniformly distributed (Table 3). There was no obvious difference in the visual quality of marbles with or without EF treatment. The Ct product value of 263.58 g h/m\({}^{3}\) from the marble fumigation trial appeared to be much greater than what was expected from 35 g/m\({}^{3}\) EF treatment for 4 h: on the basis of previous information, the maximal Ct product should be around 140 g h/m\({}^{3}\) with \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Nursery Plants**} & \multirow{2}{*}{**Ct Products** **(g h/m\({}^{3}\))**} & \multirow{2}{*}{**Chlorophyll Content (Mean \(\pm\) SE)**} & \multirow{2}{*}{**Hue Value (Mean \(\pm\) SE)**} & \multirow{2}{*}{**Overall Injury**} \\ \cline{3-4}  & & & & & & \\ \cline{3-4}  & & & & & & \\ \hline _F. retusal_ & 60.12 \(\pm\) 1.51 \({}^{\text{a}}\) & 61.51 \(\pm\) 2.15 \({}^{\text{a}}\) & 17.66 \(\pm\) 1.56 \({}^{\text{a}}\) & 17.50 \(\pm\) 0.91 \({}^{\text{a}}\) & 0 \\ _F. berghalensis_ & 61.39 \(\pm\) 1.20 \({}^{\text{a}}\) & 59.33 \(\pm\) 2.49 \({}^{\text{a}}\) & 18.19 \(\pm\) 2.03 \({}^{\text{a}}\) & 18.44 \(\pm\) 1.69 \({}^{\text{a}}\) & 0 \\ \hline \end{tabular}
\end{table} 
Table 2: Effect of ethyl formate (EF) fumigation (35 g/m\({}^{3}\) for 4 h at 15 \(\pm\) 1 \({}^{\circ}\)C) on leaf chlorophyll content, leaf hue value, and overall plant injury of two species of imported potted rubber plants (_Fiscus retusa_ and _F. benghalensis_) after 30-day postfumigation growth period in a greenhouse. Different letters on means indicate significant differences between EF treatment and untreated control by _t_-test at \(p\) < 0.05. \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Applied Dose (g/m\({}^{3}\))**} & **EF Sampling** & **Ct Products** & **No. of _R. speratus_** & **No. of _R. speratus_** & **Mortality of _R._** \\  & **Location Inside Tent** & **(g h/m\({}^{3}\))** & **Workers Tested** & **Workers Dead** & _speratus Workers (\%)_ \\ \hline Untreated control & - & - & 661 & 0 & 0 \\ \hline Front & 279.87 & 691 & 691 & 100 \\
35 & Middle & 267.93 & 606 & 606 & 100 \\ Rear & 242.94 & 687 & 687 & 100 \\ \hline \end{tabular}
\end{table} 
Table 3: Concentration \(\times\) time (Ct) products (g h/m\({}^{3}\)) of and the mortality of _Reticulitermes speratus_ workers from 35 g/m\({}^{3}\) EF fumigation at 15 \(\pm\) 1 \({}^{\circ}\)C for 4 h treated on imported marble in commercial-scale fumigation trials conducted in a 33.6 m\({}^{3}\) tranquilin tent. minimal sorption and gas leak. This may have been due to the low EF sorption in marble. In this study, the actual amount of EF injected into the tarquain tent was 1.17 kg based on the EF dose of 35 g/m\({}^{3}\) in 33.6 m\({}^{3}\) tent. Considering the volume of loaded marble (21 m\({}^{3}\)) inside the tent, the actual EF dose could be considered to be 1.17 kg/12.6 m\({}^{3}\) if marble was completely impermeable to EF gas. This translates to 90 g/m\({}^{3}\) dose of EF (for 4 h), which could result in a Ct product of 360 g h/m\({}^{3}\) with zero sorption and leakage. Thus, with 30% EF sorption, as observed from the marble sorption study, the Ct product of 263.58 g h/m\({}^{3}\) observed in the scale-up study seems possible. This result suggests that an even greater loading ratio for marble (greater than 60% \(v/v\)) could be opted during commercial-scale EF fumigation when other logistics do not limit the use of higher loading ratio.