## 4 Discussion  
_C. lactucae-sativa_ is an airborne plant pathogen that can infect dozens of plants, and brassicaceae plants are one of its main targets [4; 5]. The fungus is difficult to eliminate and can be resistant to fungicides due to its extensive reliance on fungicides [28]. Moreover, in organic farming, the incidence and severity of leaf spot disease on lettuce are regularly observed to result in a reduction in product quality and quantity [2]. Cercospora leaf spot disease has important economic implications around the world and has caused major damage to lettuce cultivation in Thailand [1]. Therefore, the application of NTP to inactivate fungal growth and control leaf spot disease is an interesting proposition. NTP at atmospheric pressure is composed of several reactive species such as O', OH and NO\({}_{2}\), which account for chemical and physical changes in biological materials [29]. Therefore, RONS are considered to play an important role in the decontamination and inactivation of microorganisms [30]. The mechanisms of NTP that are involved in the inactivation of microorganisms are still elusive and inconsistent due to complex plasma and microbial systems. However, thus far, there are two main categories of mechanisms: biological and physical [31]. In biological mechanisms, UV irradiation generated by NTP causes damage to cells, lipid peroxidation, protein modulation and apoptosis induction [32]. Physical mechanisms involve electrostatic disruption and electroporation [13; 33]. Figure 3: Antifungal efficacy of non-thermal atmospheric pressure gliding arc (GA), tesla coil (TC) and dielectric barrier discharge (DBD) plasmas on the inactivation of Cercospora lactucae-sativa conidial germination after 5 min exposure to each plasma, observed 4 and 24 h after incubation. Conidial germination was completely inactivated in all plasma treatments. C = conidia; Gt = germ tube; HP = hypha. NTPs have been applied to inhibit, inactivate and eliminate many important fungal phytopathogens such as _Athelia rolfsii_ which causes southern blight disease on lettuce [34]; _Aspergillus niger_, which contaminates palm fruits [35]; _Fusarium graminicearum_, which causes Fusarium head blight in wheat [36]; and _Colletotrichum gloeosporoides_, which causes anthracnose disease in chili [18]. The results of the application of NTP demonstrate the complete inactivation of fungal growth (in both mycelial and conidial germination) and the inactivation of fungal pathogenesis [14]. In this study, the inactivation of mycelial growth differed depending on the type of plasmas. DBD plasma showed the strongest fungal inhibition due to its wide discharge plate, which increased the area of plasma available to interact with the fungus [33]. In contrast, GA and TC plasmas were plasma jet types, in which the plasma was generated through a single plasma dispenser [12]. The fungal mycelia that were not exposed to plasma (the non-treated control) could grow regularly. Therefore, DBD plasma was considered the most effective and capable non-thermal atmospheric pressure plasma for the inactivation of the mycelial growth of _C. lactucae-sativa_. However, non-thermal atmospheric pressure GA, TC and DBD plasmas inactivated the conidial germination of _C. lactucae-sativa_ completely after exposure for 5 min. Accordingly, fungal pathogenicity was examined by spraying conidia, which were exposed to all three plasmas for 5 min, on lettuce leaves. The results showed that the disease incidence, severity and severity index were completely inactivated compared to the non-treated control. [PERSON] et al. [37] used air plasma surface barrier discharge (SBD) on inactivation of conidia germination of _Aspergillus niger_ and showed that after exposure for 2 min, the conidia of _A. niger_ were completely inactivated. it was concluded that the dominant active species produced in the plasma were nitrogen species analyzed by optical emission spectroscopy (OES).