Anthracnoses are not the only diseases favored by wet spring weather.
One- and two-year old aspen suckers are showing heavy shoot blight infections
caused by the fungus, Venturia tremulae. As you walk into a regenerating
stand, you?ll notice the new leaves and leaders are blackened and bent
over (shepherd's crook). Growth stops for the season and, if the
shoots are repeatedly infected for a number of years, this shoot blight
can cause stem deformation and even death. Infections that occur
in mid- to late-summer simply cause a leaf spot. This shoot blight is of
little or no economic importance, but serves to thin out aspen sucker stands.
Aspens older than five years are usually not affected.
Lirula needle blight of spruce
Lirula needle blight has been found to be a minor disease of spruce in
some areas, and one causing serious injury when present in other areas.
The later seems to be true for a few trees found in a Fillmore County shelterbelt.
This is only the second time we have seen this leaf disease affecting spruce
in southeastern Minnesota in the last few years. Fungicide applications
of chlorothalonil may control Lirula with two applications, one each in
early June and July.