## 4 Discussion  
Crop diseases remain a critical constraint to yield and quality in modern agricultural production. Our disease surveys in Liaoning Province revealed significant regional variations in the disease prevalence. Beipiao City (Chaoyang) exhibited notably high disease indices (48.58 for non-straw return vs. 51.52 for straw return), followed by Fumeng County, Fuxin (35.64 vs. 42.78), indicating severe disease pressure in these areas. Particularly striking was the 20% increase in the northern corn leaf blight disease index under straw return conditions in Fumeng County. Additionally, at the trial site of Fumeng County, modest increases in _Fusarium_ stalk rot incidence were observed with straw retention, providing field evidence for subsequent analyses. The deployment of disease-resistant cultivars represents the most cost-effective control strategy by eliminating additional inputs. However, widespread adoption faces constraints from limited genetic resources. While advances in genetic engineering, such as the discovery of _ZmLecRK1_ enhancing the resistance to soil-borne diseases [21], offer potential solutions, identifying broad-spectrum resistance genes remains time- and resource-intensive. Moreover, rapid pathogen evolution threatens the durability of resistance [22]. Conservation tillage systems present unique challenges through straw retention. Although beneficial for soil health, surface residues modify pathogen survival environments, potentially accelerating adaptive evolution and resistance breakdown [23,24]. Our findings demonstrate that straw return significantly exacerbates both northern corn leaf blight (_Exserohilum turcicum_) and stalk rot (primarily _Fusarium_ spp. ), consistent with previous reports on residue-mediated pathogen survival and corroborating our Liaoning observations. This phenomenon is well-documented in other pathosystems; for instance, [PERSON]'s bacterial wilt (_Clavibacter michiganensis_ subsp. _nebraskaensis_) prevalence strongly correlates with residue retention in reduced tillage systems [25]. We hypothesize that straw return increases the initial inoculum loads and improves the overwintering conditions, while continuous maize monoculture may further intensify pathogen accumulation, creating a detrimental pathogen-residue-host feedback loop [25]. Chemical control remains an important component of integrated management. [PERSON] et al. demonstrated 60% control efficacy against NCLB using prothioconazole + trifikovstrobin at pre-tasseling [26]. Our trials with locally used fungicides (e.g., difenoconazole, triadimefon) in Fuxin confirmed their effectiveness for residue-borne disease suppression. Building on previous work with live _Trichoderma harzianum_ SH2303 and fungicide combinations showing 60% field efficacy against Southern Leaf Blight [27], we innovatively employed inactivated _Trichoderma_ fermentate with difenoconazole for residue treatment. We developed a novel chemo-biological approach for pre-sowing straw treatment. Chemical pretreatments (e.g., urea-NaOH) disrupt lignin matrices to accelerate decomosi \begin{table}
\begin{tabular}{c c c c} \hline
**Treatment Number** & **Treatment Combinations** & **Disease Incidence (\%)** & **Disease Inhibition Rate (\%)** \\ \hline
1 & 10\% Definoconazole & 2.15 \(\pm\) 1.18 & 2.09 \(\pm\) 2.13 \\
2 & 10\% Definoconazole + & 0.61 \(\pm\) 0.70 * & 71.03 \(\pm\) 71.51 \\  & Biocontrol agent & & \\
3 & 15\% Triadimefon & 4.61 \(\pm\) 6.01 & 0 \\
4 & 0.3\% Tetramycin & 2.70 \(\pm\) 1.76 & 0 \\
5 & 250 g/L Azoxystrobin & 2.34 \(\pm\) 2.47 & 0 \\
6 & 50\% Carbedazim & 3.28 \(\pm\) 2.51 & 0 \\
7 & Biocontrol agent & 3.98 \(\pm\) 0.64 & 0 \\
8 & CK & 2.11 \(\pm\) 2.47 & - \\ \hline \end{tabular} Asterisks indicate statistically significant differences between treatment and control groups as determined by Student’s \(t\)-test (*, \(p<0.05\)).  
\end{table} 
Table 6: Inhibitory effects of different fungicides on _Fusarium_ stalk rot after straw spray application.