Study on the synergistic control of walnut brown spot by Bacillus amyloliquefaciens and pyraclostrobin

Walnut brown spot disease is one of the most significant diseases affecting walnut trees,caused by the pathogen Alternaria alternata (Fr.) Keissler. Currently, chemical control is theprimary means of managing walnut brown spot disease, but there are no registered controlagents specifically for this disease. Therefore, developing effective agents to control walnutbrown spot disease and achieve reduction and efficiency is an urgent problem. Biocontrolbacteria can inhibit the growth of pathogens by producing active ingredients such aslipopeptides. Moreover, their spores can survive in adverse environments, allowing them toremain effective over time. Additionally, biocontrol bacteria have several other mechanisms ofaction, making them an essential component of biological control strategies.The present study used the mycelial growth rate method to screen chemical agents withhigh activity against Alternaria alternata ASF1, ASC2, and AMGT3 strains. The antibacterialactivity of Bacillus amyloliquefaciens SDTB009, a biocontrol strain isolated and identified bythe research group, against the pathogen responsible for walnut brown spot disease was alsoverified. Additionally, the indoor toxicity and field effectiveness of combining the biocontrolbacteria with the screened chemical agents were evaluated for their efficacy against walnutbrown spot disease. A comparison was made between the effects of conventional chemicalfertilizer treatment and Bacillus amyloliquefaciens agent treatment on soil physical andchemical properties, soil microbial community, walnut yield and quality.