AHS Region 2/Great Lakes Newsletter
Katherine Whitten's OSU Rust
strated that these urediospores were unable to infect
healthy daylily leaves under normal laboratory conditions.
Control urediospores, maintained at ambient indoor
laboratory temperatures throughout the experiment, never
lost their ability to either germinate in artificial medium or
to infect healthy daylily leaves.
Reported by John Sheehan, Madison, Wisconsin.
These results suggested that northern gardeners with
Katherine Whitten, graduate
daylily rust infestations could kill off the rust (with the
student in Plant Pathology at
help of Mother Nature providing freezing temperatures
The Ohio State University,
during the winter). This report was wonderful news to
gave us an update on the
daylily growers in Zones 6 and lower.
daylily rust (Puccinia
Dr. Nameth suggested that northern gardeners should be
hemerocallidis) research being
sure to remove all dead/dying daylily foliage when the
carried out in Dr. Steve
gardens were being put to bed for the winter. This step
Nameth's laboratory at the
would minimize any daylily spores present in the infected
Ohio State University (OSU)
garden as well as remove a potentially insulating microen
in Columbus, Ohio.
vironment which might keep the infected leaves above the
Ms. Whitten reviewed the
experimental results from
Ms. Whitten prefaced her remarks at the 2003 Symposium
2001 2002 and compared
by saying that this present winter (2002 2003) had been
them with results from this
much colder than the previous winter (2001 2002). The
Plant Pathology, OSU.
year. She also discussed two
average low winter temperature in Columbus, Ohio, last
Image: Lee Alden, Michigan.
other daylily rust research
year was 29 degrees Fahrenheit. The average low winter
projects being carried out in
temperature this winter has been 20 degrees Fahrenheit.
the Department of Plant Pathology.
A similar experimental protocol was set up this winter.
At the Region 2 Symposium in 2002, Dr. Nameth pre
The analysis of infected daylily leaves exposed to the
sented preliminary data suggesting that the urediospore
outside air showed that the urediospores exposed to the
stage of daylily rust may not overwinter in the northern
cold lost both the ability to germinate in artificial medium
regions of the U.S. In November of 2001 researchers in Dr.
to infect healthy daylily leaves.
Nameth's laboratory exposed a series of rust infected
These results taken in conjunction with the results reported in
daylily leaf fragments to outside ambient air conditions (in
2002 may suggest that in regions of the U.S. where the
Columbus, Ohio). At bi weekly intervals samples were
average low winter temperature falls to 29 degrees Fahrenheit
taken back to the lab to be tested for the ability of the
( or lower), the rust urediospores will be killed by the cold.
urediospores to germinate in an artificial medium OR to
Revision Note from Katherine Whitten:
We do not know the exact
infect healthy daylily leaves.
temperature at which the urediospores are inactivated. I will be working
on this next winter. It could be that the average low means nothing and
Analysis of samples from 13 Nov 2001 through 8 Mar
that it is just a certain low temperature that the spores need to be
2002 showed that these urediospores could germinate in
exposed to for a short period of time.
the artificial medium. However, and more to the point,
TRANSLATED INTO SIMPLE ENGLISH: If you have a
samples brought in and tested after 11 Dec 2001 demon
garden infected with daylily rust in the fall and your
average low winter temperature is at least 29 degrees (or
lower), the rust may be killed off by the time spring
Region 2 Newsletter editor.
Again, so many of you volun
Ms. Whitten also reported that the Nameth Laboratory is
teered to write up the wonder
actively working on two additional daylily rust projects to
ful Symposium presentations.
Yours is the special dedication
answer the following two questions:
I have found so admirable in
Are there some daylily introductions that are more resistant
to infection by urediospores?
For the past year the Plant Pathology Department at OSU
has been collecting daylilies from AHS members. The
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