Know
the difference between black knot and black spot? If
not, you may want to contact the
Iowa State University Plant Disease Clinic.
Last year almost 5,000 Iowans did just that. The clinic
received 1,719 samples - including whole plants, dry
leaves, green leaves, stems, roots, branches and twigs -
in the mail. The staff also answered 3,267 calls,
e-mails, faxes and letters about plant problems.
Paula Flynn and Christine Engelbrecht, the two clinic
diagnosticians, investigate and answer each inquiry with
possible solutions or questions for more information.
"We're the Crime Scene Investigators, or CSI, when it
comes to plants," said Flynn, extension program
specialist in plant pathology. "We put all the clues
together to come up with the best answer."
Diagnosing a problem can take 30 seconds or several
weeks. Flynn said it's important to offer answers as
quickly as possible because gardeners, farmers and
landscapers want suggestions on how to manage a
potential problem.
"We get a lot of garden and ornamental plant samples. We
also get many samples from extension offices," Flynn
said. "Gardeners often go to the county office and if
those offices need more assistance or laboratory tests,
they send samples to our clinic."
During the growing season the daily mail brings in boxes
filled with mysteries. Some samples include photographs,
which provide additional diagnostic clues. Photos
showing the area where the plant or tree is growing may
point to other problems.
"The more we have in terms of samples and pictures the
more we can do," Flynn said.
"We also need detailed descriptive background
information. Was there construction in the area? How
much do you water? Or is there a downspout near a
stressed tree?"
Flynn showed one photo she received that accompanied a
sample of brown leaves. In the photo, a parking lot,
sidewalk and cemetery surround a tree. Flynn said her
first diagnosis would include a combination of
compaction problems and drought stress.
"We were thankful for the picture because it pointed to
site-related problems. If they had only sent in browning
leaves, we would have followed-up with questions." Flynn
said.
Plant problems can be caused by an endless number of
factors that include insects, diseases, soil conditions
and weather.
"You would
think we would have the same diseases show up over and
over. But there are so many combinations of contributing
factors, and some problems have four or five. Those are
the hard ones," Flynn said.
The clinic is located on the second floor of Bessey
Hall. In a medium-sized room lined with cupboards,
microscopes stand at attention on polished, black
counters, waiting for spring.
"It's
quiet now but it gets crazy in here between May and
August. It's a juggling act," Flynn said.
She and
her staff are preparing for a busy growing season. Asian
soybean rust was discovered in North America for the
first time in November. The disease was first found in
Louisiana and since has been found in eight southern
states after being carried into the area by hurricanes.
Flynn and
Engelbrecht members of the Iowa Soybean Rust Team, which
was formed two years ago to collect and disseminate
information on how to manage the disease. The clinic
along with the rust team began training crop specialists
last summer on how to diagnosis the disease. Iowa leads
the nation in soybean production, and if soybean rust
moves into Iowa, it could cause increased production
costs and decreased yields.
"It's an uncertainty, but we're prepared to answer
questions," Flynn said.
The clinic's turn-around-time was less than five days
for 73 percent of the inquiries it received last year.
Tree samples made up half of the inquiries and field
crop questions totaled 13 percent, followed by questions
about perennials, annuals, woody ornamentals, fruit
trees, turfgrass and vegetables.
The clinic opened in 1956 in response to another major
problem - Dutch elm disease. For 32 years faculty and
graduate students handled client questions. In 1989,
Flynn was hired as the first full-time diagnostician.
Widespread diseases such as Dutch elm, which are
imported into North America, prove to be the most
harmful, said Engelbrecht.
"Native plants don't have resistance to new diseases and
that's why they are so devastating," Engelbrecht said.
The newest disease threat to trees in Iowa is sudden oak
death. Last spring, an alert went out to several states
after seedlings carrying sudden oak death were shipped
from California. Engelbrecht helped inspectors analyze
woody plant samples from area landscape and garden
stores, which helped prevent the disease from entering
Iowa.
So what's the difference between black knot and black
spot? Engelbrecht's answer: Black knot is a fungal
disease that affects cherry trees and causes large black
galls to form on the branches. Black spot is a fungal
disease that affects roses and causes black spots to
appear on the leaves.
