*3.8. In Vitro Antifungal Activity*

Maximum inhibition (85.2 ± 0.7%) was seen in the case of *Alternaria alternata* in a mancozeb-loaded formulation at 0.5 ppm and is almost the same as commercial mancozeb at 1.5 ppm (Figure 5a), which might be attributed to the formulation's increased zeta potential. Mancozeb-loaded CSGA NPs had the best antimicrobial efficacy against *S. lycopersici* at 1.0 and 1.5 ppm (100% inhibition at both concentrations). These findings matched prior research in which carbendazim-loaded polymeric nanoparticles were evaluated against *F. oxysporum* and *A. parasiticus* and showed 100% fungal suppression at 0.5 and 1.0 ppm [23]. In contrast, it exhibited 62.1 ± 0.7% inhibition at 0.5 ppm, equivalent to commercial mancozeb (56.1 ± 0.7%). Table 3 and Figure 5a,b) indicate the percentage inhibition shown by NPs.

**Table 3.** In vitro antifungal efficacy of mancozeb-loaded (1.0 mg/mL) CSGA-1.0 nanocomposites.


Each value is a mean of a triplicate. Mean ± standard deviation followed by the same letter in the treatment column indicate that values are not significantly different at *p* ≤ 0.05, as determined by a *t*-test.

Nanofungicides have better efficiency than traditional fungicides owing to the formation of reactive oxygen species (ROS), membrane permeability due to their tiny size, and enzyme-related defense responses in plants against fungi [22,42]. Another study obtained more substantial repellents (around 80%) against two key agricultural pests (whitefly (*Bemisia tabaci*) and spider mites) while working with a hydrogel containing botanical

repellents encapsulated in zein nanoparticles [43]. In previous research, *Rhizoctonia* sp. and *Alternaria* sp. strains were shown to be the most susceptible to chitosan–zinc nanocomposites, followed by chitosan–copper nanocomposites [24].

**Figure 5.** In vitro antifungal efficacy of blank- and fungicide- (1.0 mg/mL) loaded CSGA NPs at three concentrations (0.5, 1.0, and 1.5 ppm) using the mycelium inhibition method against tomato pathogens (**a**) *A. alternata*, (**b**) *S. lycopersici*; C—control, PC—pure control (Petri plates with PDA alone), N1—blank CSGA NPs, N1F—fungicide, F—fungicide.
