Ecology, genetic variation, and biological control of the artillery fungus (Sphaerobolus stellatus Tode:Pers.)

Twenty-five landscape mulches were evaluated, both in the field and laboratory, to determine products that supported or inhibited colonization and sporulation by the artillery fungus (Sphaerobolus stellatus Tode:Pers). Although most types of mulch eventually supported the artillery fungus, some supported more colonization than others. The artillery fungus did not grow or sporulate well on mulches made from large pine bark nuggets, Atlantic white-cedar, or cypress.; Isolates (22) of S. stellatus collected from substrates in Connecticut, North Carolina, and Pennsylvania were evaluated for genetic variation within the ITS1 region of rDNA. Two major clades were identified. Isolates from Connecticut and North Carolina were different from the majority of the Pennsylvania isolates. Sphaerobolus stellatus may contain two ITS1 types.; Three strains of the fungus Trichoderma harzianum Rifai and two strains of the bacterium Bacillus subtilis (Ehrenberg) Cohn were evaluated for their ability to suppress colonization and sporulation of S. stellatus on oatmeal agar. All five biological control agents inhibited growth of S. stellatus, but efficacy depended on time of application. Simultaneous inoculation of agar with S. stellatus and the biocontrol agents, as well as inoculation of biocontrol agents 14 days prior to S. stellatus, resulted in complete inhibition of S. stellatus. Inoculation of agar with biocontrol agents 14 days after inoculation with S. stellatus reduced, but did not completely suppress S. stellatus colonization and sporulation. In this experiment, gleba (spore masses) treated with all strains of T. harzianum and strain GBO3 of B. subtilis did not germinate, but 13% of gleba treated with strain MBI 600 of B. subtilis did germinate after re-isolation of gleba from the original agar plates. Trichoderma harzianum was more effective than B. subtilis as a biocontrol agent.