Bacillus strains as biocontrol agents against fungi associated with defoliation in Pinus patula, Pinus montezumae, and Pinus pseudostrobus

Abstract Worldwide, forest loss is attributed primarily to fires, pests, and diseases. Among them, fungal pathogens are frequently associated with important diseases in pine forests, with dreadful consequences. In the mountain range of northern Puebla, Mexico, phytopathogenic fungi cause defoliation in Pinus patula Schl. et Cham (Pinales: Pinaceae), Pinus montezumae Lamb. (Pinales: Pinaceae), and Pinus pseudostrobus Lindl. (Pinales: Pinaceae). The standard treatment for controlling fungal diseases is the application of highly toxic fungicides. Given that these products are inefficient and pose risks to biodiversity and human health, it is necessary to develop effective and environmentally friendly alternatives. In this context, this investigation proposed the use of rhizospheric forest bacteria as antagonists against phytopathogenic fungi under in vitro , greenhouse, and field conditions. Fungi associated with pine defoliation were isolated and identified to evaluate their responses against Bacillus and Peribacillus strains. Among the most frequently occurring fungal genera associated with the three pine species, three were shared: Clonostachys , Curvularia , and Myrmaecium . In addition, foliar application of Bacillus thuringiensis (Bacillales: Bacillaceae) and Peribacillus simplex (Bacillales: Bacillaceae) reduced lesion incidence and the severity index of symptoms associated with fungi in a forest system up to 50%. These results are promising for research on biological alternatives for the control of fungi in forest systems.