## 3 Results
### Survey of Commonly Used Fungicides in the Corn Fields of Fuxin Region  
Currently, chemical fungicides remain the predominant approach for disease control. To investigate fungicide usage patterns, we conducted a survey among farmers in Fuxin City where the northern corn leaf blight severity was exacerbated under straw incorporation practices. The survey revealed five main fungicides employed in this region: difenoconazole, triadimefon, tetramycin, azoxystrobin, and carbendazim. Notably, difenoconazole was the most widely adopted, being utilized by over 40% of the respondents (Figure 1). \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**City**} & \multirow{2}{*}{\begin{tabular}{c} **County** \\ **(Latitude and Longitude)** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **Northern Corn Leaf Blight** \\ **(Disease Index)** \\ \end{tabular} } & \multicolumn{2}{c}{\begin{tabular}{c} **Fusarium Stalk Rot** \\ **(Disease Incidence, \%)** \\ \end{tabular} } \\ \cline{3-6}  & \begin{tabular}{c} **Non-Straw** \\ **Return** \\ \end{tabular} & \begin{tabular}{c} **Straw Return** \\ \end{tabular} & \begin{tabular}{c} **Non-Straw** \\ **Return** \\ \end{tabular} & \begin{tabular}{c} **Straw Return** \\ \end{tabular} \\ \hline \multirow{3}{*}{Shenyang} & Kangping & 11.11 & 12.25 & 0 & 0 \\  & \
\begin{tabular}{c} Faku \\ (42.50\({}^{\circ}\) N, 123.40\({}^{\circ}\) E) \\ \end{tabular} & 12.04 & 13.08 & 13.89 & 11.52 \\ \multirow{3}{*}{Fushun} & Qingyuan & 23.82 & 26.54 & 19.00 & 18.75 \\  &
\begin{tabular}{c} Beiping \\ (41.80\({}^{\circ}\) N, 120.75\({}^{\circ}\) E) \\ \end{tabular} & 48.58 & 51.52 & 6.00 & 7.52 \\ \multirow{3}{*}{Fuxin} & Fumeng & 35.64 & 42.78 & 12.00 & 12.80 \\  & Fengcheng & 32.86 & 28.95 & 7.00 & 8.00 \\ \hline \end{tabular}
\end{table} 
Table 4: Disease investigation (northern leaf blight and stalk rot) in selected areas of Liaoning, China. Figure 1: Survey of commonly used fungicides in corn fields of Fuxin region. (**a**): Statistics of the number of farmers using each pesticide in Fuxin City; (**b**): proportion of farmers using each pesticide. This survey only recorded single-component pesticide usage and did not include mixed formulations. A total of 45 farmers from the entire Fuxin City participated in the survey. Based on these findings, we selected these fungicides to evaluate their efficacy in controlling the primary pathogen infections associated with straw incorporation. Particular emphasis was placed on investigating difenoconazole's performance, as optimizing the application methods for this conventional fungicide could significantly improve local disease management practices. Synergistic Effect of Difenoconazole and Trichoderma Fermentate in Controlling Northern Corn Leaf Blight and Stem Rot  
The results demonstrated that the combined application of fungicides with biocontrol agents exhibited superior efficacy in disease control. In spring 2024, prior to souring, we conducted a field experiment in Fumeng County, Fuxin City, where straw mulch was treated with the aforementioned fungicides according to the commercial product specifications, followed by normal souring. Additionally, we incorporated a _Trichoderma_ fermentate biocontrol agent developed by Shanghai Jiao Tong University (application followed the developer's guidance; see Table 2) to explore the potential synergistic effects when combined with the widely used difenoconazole. Untreated plots served as controls. For leaf blight control, Treatment 2 (difenoconazole + biocontrol agent) showed optimal performance with a disease index of 14.96 and inhibition rate of 72.40 \(\pm\) 0.52%, significantly outperforming other treatments. Treatment 1 (difenoconazole alone) achieved 56.21 \(\pm\) 2.73% inhibition (disease index 23.74), while Treatment 5 (azoxystrobin) and Treatment 7 (biocontrol agent) showed moderate efficacy with 69.91 \(\pm\) 2.24% and 67.11 \(\pm\) 1.44% inhibition, respectively. Treatment 6 (carbendazim) demonstrated the weakest effect (46.11 \(\pm\) 5.27%).