EFFECTS OF PINE BARK EXTRACTS AND PINE BARK POWDER ON FUNGAL PATHOGENS, SOIL ENZYME-ACTIVITY, AND MICROBIAL-POPULATIONS

Pine bark extracts and pine bark powders were evaluated in vitro and i n greenhouse experiments for effect on fungal growth and infectivity, soil enzyme activity and soil microbial populations. Agar media were f ormulated using powdered fresh or composted pine bark and pine bark ex tracts prepared by refluxing pine bar powder with acid, neutral, and a lkaline solutions Growth of Rhizoctonia solani, Sclerotium rolfsii, Fu sarium oxysporum f. sp. vasinfectum, Phytophthora parasitica, Alternar ia solani, and Sclerotinia sclerotiorum was reduced on agar containing either fresh or composted pine bark powder, whereas growth of the non parasitic fungus Penicillium citrinum was enhanced. Growth of parasiti c fungi on media containing pine bark extracts was varied. However, ex tracts prepared using alkaline solutions reduced the growth of more of the fungi tested and to a greater extent than extracts prepared with neutral or acid solutions. In greenhouse experiments, emergence of len til (Lens culinaris) was significantly increased by the addition of fr esh or composted pine bark powder to soil inoculated with either R. so lani or S. rolfsii. Increases in soil trehalase activity were correlat ed with increases in total populations of indigenous fungi and specifi cally with species of Penicillium and Paecilomyces. Pine bark powder d ecreased fungal growth in vitro and reduced disease incidence in green house experiments while altering soil fungal populations. Analysis of soil trehalase activity provides a simplified means for monitoring soi l fungal populations leading to a more complete understanding of soil microbial ecology. (C) 1994 Academic Press, Inc.