Long-term dry preservation of viable mycelia of two mycoherbicidal organisms

The production of large amounts of fungal spores for preservation and formulation are considered constraints to effective use of fungal biocontrol agents. Few successful attempts have been made to store fungal mycelia alone. Late log-phase liquid fermenter cultured isolated mycelia of two Fusarium spp. specific to the parasitic broomrapes (Orobanche spp.) from fermenters were formulated in alginate beads or in ‘Stabileze’ (starch, sucrose, corn oil, and silica) and air-dried. ‘Stabileze’ formulations exhibited <30% loss of mycelial viability for >9 months and retained pathogenicity to the weed for over a year, while mycelia harvested earlier, and conidia from liquid culture exhibited >40% loss of viability. Mycelia from liquid culture yielded >20 times more colony forming units (cfu) of F. arthrosporioides and >2 times more cfu of F. oxysporum than spores at late log phase. Efficient formulation of mycelia should significantly change the economics of biocontrol.