|Venturia Shoot Blight -
Sexual Stage: Venturia populina,
Asexual Stage: Pollaccia spp.
Jane Taylor, USDA Forest Service,
HOSTS: Aspen, cottonwoods, and poplars.
leaves develop irregular brown to black areas and become distorted and
curled. Leaf stems may become constricted at the base. The fungus
spreads down through the shoot which blackens and curls to resemble a
CYCLE: Spores of
this fungus overwinter in fallen leaves as well as previously diseased
stems and twigs. Spores are wind-blown early in the season and infect
newly expanding leaves and shoots. During extended wet periods,
secondary infection may result when fungus spores are rain splashed to
other parts of the tree growth. Infection is most rapid at 60 - 77°
F. when leaves are wet.
nitrogen fertilization- succulent growth is most susceptible. Keep
irrigation water off of trunk, branches, and leaves. Prune infected
shoots out on a hot, dry day. Rake and destroy fallen leaves during the
growing season to reduce secondary infection. Protect new growth with
sulfur during wet weather and temperatures >60° F.