Studying the Antifungal Effects of Ageratina adenophora (Sprengel) R. King and H. Robinson (=Eupatorium adenophorum Sprengel) as a Bio-Fumigant Plant Alone and in Combination with Biochar Against Pythium aphanidermatum (Edson) Fitz

<i>Pythium</i> spp. are soil-borne pathogens that cause damping-off and root rot diseases in many plant species such as cucumber. In the current study, the effect of dried roots-stems and leaves of <i>Ageratina adenophora</i> (Sprengel) R. King and H. Robinson (=<i>Eupatorium adenophorum</i> Sprengel) alone and in combination with pyrogenic biomass biochar to control <i>Pythium aphanidermatum</i> (Edson) Fitz was assessed. In four treatments of leaves, roots-stems, leaves + biochar, and roots-stems + biochar, it was observed that the treatment with leaves at an E_max (maximal effective concentration on control fungi) of 79 g/kg of soil had the most antifungal effect on <i>P. aphanidermatum</i>. Also, the C_max (the highest level of control) increased with time and reached 82.4% and 71% on days 30 and 60, respectively. The highest cucumber fresh fruit weight and the highest height of the stems in the greenhouse were observed in leaf treatment of <i>A. adenophora</i>. Biochar did not have any remarkable controlling effect on <i>P. aphanidermatum</i>, and its population increased. The main compounds extracted from the dried leaves and roots-stems of <i>A. adenophora</i>, including α-pinene, nonanone, hexahydronaphthalene, 3-undecanone, muurolene, and heneicosane, had antifungal properties. We concluded that the leaves of <i>A. adenophora</i> have the potential to be used as a bio-fumigant for <i>P. aphanidermatum</i> management.