American chestnut sprout survival with biological control of the chestnut-blight fungus population

The American chestnut trees in Connecticut were reduced to understory shrubs by an imported fungus that causes lethal cankers. Chestnut blight disease was first reported in the United States in 1904, and in Connecticut in 1907. Hypovirulence is a virus disease of the fungus that reduces its virulence enough to allow the defense systems of the trees to restrict the fungus to the outer bark. Blight cankers on chestnut sprouts in a 1.4 ha wood-lot in central Connecticut were treated with hypovirulent strains from 1982 through 1986. Stem diameters were measured periodically. Stem size distribution has stayed consistently higher than in a comparable forest area with no treatment.