forcing Rhytisma

Jim Worrall jworrall at
Tue Nov 7 13:21:05 EST 1995

In article <kh11-011195125957 at>, kh11 at (Kathie T.
Hodge) wrote:

> Tar spot is all over the maple trees in my front yard.  Does anyone know
> how to force Rhytisma spp. to fruit so I can look at the ascomata, or do I
> have to wait for spring?
I have used Tarspot in a spring class by collecting the downed
leaves in winter, soaking them in a stream of water, and incubating
them in petri dishes on a moist paper towel near a window.  I think
it took about a week or two.  Only about 5-10% opened nicely, but
those were worth it.

I can't tell you exactly what month it was, except it was after
February and it was still frozen outside.  I suspect the
ascomata mature during late fall and early spring.  I doubt you
could force them this early, but who knows.  If I do it
again I will try alternating them between a refrigerator and
a window shelf during incubation.

Jim Worrall

Jim Worrall
SUNY College of Environmental Science & Forestry
Syracuse NY 13210

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