Capsicum Endophytic Bacterial Strain LY7 and Prochloraz Synergistically Control Chilli Anthracnose

Chilli anthracnose is a major infectious disease of the genus Capsicum. Chemical control is the primary means of controlling this disease; however, the excessive use of chemical pesticides can adversely affect ecological security and human health. Here, our aim was to explore the synergistic effects of chemical and biological pesticides in the control of chilli anthracnose. The bacterial strain LY7, which is antagonistic to the anthracnose-causing fungus Colletotrichum scovillei, inhibited the growth of C. scovillei by 83.52%. Through morphological and genetic analyses, this strain was identified as Bacillus velezensis. Then, the compatibility of LY7 with three common chemical fungicides was determined. The in vitro protective and therapeutic efficacies of the 1 × 109 CFU/mL (colony-forming unit/mL) bacterial solution were 66.38% and 35.18%, respectively, but both were significantly lower than those of prochloraz, the most compatible fungicide. We then conducted field efficacy trials to elucidate the best combination of prochloraz and LY7; the highest control efficiency was achieved with a suspension of 1.0 × 108 CFU/mL of LY7 mixed with 0.75 g/L prochloraz (3:7 ratio). Electron microscopy revealed the inhibitory effects of LY7 and prochloraz on C. scovillei mycelial growth. These results suggest that an LY7-based biofungicide can partially replace prochloraz, serving as an integrated management strategy to control chilli anthracnose.