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I'm Tom Zinnen. I work here at the UW-Madison Biotechnology Center and also for UW Extension Cooperative
Extension, and on behalf of those two groups and our others partners, the Wisconsin Alumni
Science Alliance and Wisconsin Association, the UW Madison
We do this every Wednesday Public Television, thanks again for coming to Wednesday Nite at the Lab.
Brian Hudelson. He is affectionately known Tonight I'm delighted to be able to introduce to you
as Dr. Death, we're not sure affectionately by whom, because
of his love of plant diseases.
Brian received his BS in botany, bacteriology and molecular
biometry and his PhD in plant pathology, all here from UW Madison. biology, his master's in
of the Plant Disease Diagnostics In 1998, he became the director
Clinic. The Plant Disease Diagnostic Clinic is part of the college of
Agricultural and Life Sciences
here at UW Madison and is also part of Cooperative Extension,
The clinic, and Brian in UW Extension.
particular, provides expertise in diagnosing plant disease problems, provides information
on diseases and their control to
That's everybody from farmers, a wide range of clientele throughout the state of Wisconsin.
to gardeners, to homemakers, and homeowners, and anybody in between.
He'll tell you how you can send in your plant disease samples.
It is a fee for service. >> We'll talk about that too.
"Service for fee,"
as we call it. But I think it's a wonderful
It, along with the entomology clinic, Entomology Insect Diagnostic Clinic and the Soil combination.
three, I think there might be a fourth one. >> Turf Diagnostic Lab. >> Turf Diagnostic Lab, that I'd
like everybody to be aware of because they're pretty wonderful
services to keep your plants growing.
I, too, am a plant pathologist, so it's a particular joy for me to be able to ask you to join me
Nite at the Lab. in welcoming Brian to Wednesday
[APPLAUSE] >> Brian Hudelson: Thanks very
I think our mic is on. much, Tom.
this is my first talk this week so my voice is actually doing back, pleawell.t me know. I'm finding that as I get older
that my voice tends to kind of
fade out on me when I give a lot of talks during the week, but we're good for today.
I am Brian Hudelson.
I do run what's called the Plant Disease Diagnostics Clinic, and what I'd like to do tonight is
kind of give you a brief
overview of the sort of things that I do in my job, quite
And we will talk about some specific diseases but I kind of want to talk a little bit about who we are, what we do and why
we exist. So with that, we're going to try
it a little easier for filming to save questions towards the end because I guess that makes
tonight and streaming. So if you have any questions, jot them down, and we'll get to
them at the end of the
presentation. So what is the Plant Disease Diagnostics Clinic?
The acronym PDDC is much easier to write on a package when
Clinic. We actually are part of UW people are sending me samples than Plant Disease Diagnostics
laboratory to support the County Extension and primarily what we are is basically a support
Extension offices here in the state. We have 72 counties.
Each of those counties has an Extension office, and those folks are varying levels of expertise with working with
plants. And back in the mid-1970s there was a decision that was made
some expertise to help folks in the county offices diagnose or that really there needed to be
control. identify plant diseases and provide information on disease
And the first diagnostician was Sister Mary Francis Heimann, and she retired in 1998 and I took
over from her.
And at that time, when Mary Francis started in the clinic, there was this partnership that
was put together between UW Extension and the University of Wisconsin Madison, particularly the College of Agricultural and
Life Sciences, to establish this
clinic in our Department of Plant Pathology. So that's where I'm housed.
That's where my home is.
So I'm what's called integrated staff. I'm technically a UW Extension
employee, but my home is in one of the academic departments here
And we've had this relationship for, what, about 35 years now. on campus, particularly plant pathology.
So it's been a long and very extended relationship between
Extension and the College of Ag and Life Sciences.
about the last 10 years, my lab, In addition to those particular partners, more recently, within
as well as Phil Pellitteri's Insect Diagnostic Lab, has
network of diagnostic clinics. become part of a national
This was a network that was created through a piece of legislation post-9/11.
It was actually called the Ag Bioterrorism Act of 2002, and it
together all of the land-grant provided the framework and some funding for basically linking
university diagnostic facilities that dealt with plant and insect
large network, and the whole issues in the country into a
and exotic diseases and insect idea behind doing this was to make that network more powerful in terms of monitoring for new
pests that might enter into the country. And we've been part of that for
the last 10 years.
basically on the chopping block Iat the federal level, so wee don't know whether we'll be funded with that but we're still
a partner with that.
It's been a great relationship in working with other diagnosticians around the
country.
as well. We work with all of these groups. We have a lot of other partners
I see one of my colleagues came in the back. He told me he was coming
tonight.
They have a lot of folks who This is Bob Dahl from the Department of Ag, Trade and Consumer Protection.
work with plants, dealing with insect pests and diseases as
We collaborate pretty closely with them. well.
Annette Phibbs, who I work with quite closely in diagnosing Icertain types of problems. state in the Department of Ag,
the folks at APHIS, the Animal, Plant, Health Inspection I also work quite closely with
And, in fact, we were at a Service, which is part of the USDA.
meeting this morning where we kind of gave summaries of what we had seen over the summer in
our various jobs and clinics. So there are a lot of folks working together. I have a team in my department
that I work with. There are four other Extension
McManus who is our fruit faculty in plant pathology that I work with quite closely, Patty
pathologist, Paul Esker who is our field crop pathologist, Amanda Gevens who is our
vegetable pathologist, and then Jim Kerns who is our turf pathologist.
to the parking lot today, and he's said he's talked to this group in the past. And I saw Jim as I was going out
very closely with Jim, actually, And I had an opportunity to work
So, again, my lab is a support this past summer. We'll talk a little bit about that later in the talk.
lab. We provide support for the
quite frankly what we do is expanded beyond that, and we now county extension offices, but
not only take samples from county offices but we also take
samples from a variety of other sources as well, including
willing to send me a sample I'll consultants and homeowners, quite frankly anyone who's
look at. I'm not picky.
true plant pathologist. I get very, very excited about And I must say that I do, I am a
during particular parts of this talk because I think what I do diseases. And I will act very, very goofy
I'm interacting with who are is really cool. Now, a lot of the people that
having these problems with their plants don't necessarily think
that exciting. that the diseases are really
But what I try to do is give them a sense of why I think I'm excited about these things, and
I do think plant diseases are pretty cool, but my bottom line is basically to help provide
how to manage whatever type of them with some information on
are very sick and ugly looking, disease pquite frankly.ey have. So what does the PDDC do? We look at a lot of plants that
somewhat tongue in cheek And you're going to kind of understand why I tend to be
sometimes about what I do. When you're looking at rotting, disgusting plant materials, 8,
10, 12 hours a day for an entire
year or more, I've been in this job for 13 years, you can either get really silly about it on
occasion or you can get really
depressed and I'd rather be pretty silly about it. So what do we do?
We look at plants.
into my clinic are field crops. So things that farmers are different plants. A lot of the plants that come
Those are some of the type of plants that I see from an growiagronomic standpoint.corn, I also see a lot of vegetable
samples, and I work quite closely with Amanda Gevens, again, who is our vegetable pathologist, particularly on a
disease called late blight. I'll talk a little bit more about that specifically towards the end of my talk.
We deal with fruit crops of all kinds.
summer but more so this summer, to start working more with This summer I had the opportunity, actually last
Patty went on a sabbatical and cranberries, which is a major crop here in the state.
so I was working quite closely with one of her grad students doing diagnosis on the cranberry
crops.
But we deal with basically any type of fruit crop. This was the year, quite
frankly, of raspberries.
We had more raspberries come into our clinic than any other
Not my favorite crop to work year that I can ever remember.
with for many reasons. One, they hurt when you work
I don't like plants that hurt me with them.
when I work with them, but that's the case with
And they also tend to be raspberries.
relatively difficult to diagnose the problems. There are a lot of diseases that
they can get and trying to
differentiate what disease is causing the problem can be a little bit of a challenge.
We deal a lot with evergreens.
And quite frankly my three top problems this year in the clinic
And we'll talk about pretty much were on spruce trees.
coming in. all three of those a little bit later on. But we do see a lot of conifers
Make a lot of money off the conifers, quite frankly. We also deal with deciduous
trees and shrubs like apples
with those really bright yellow spots. One of the cooler, prettier
diseases that I get to work with, a disease called cedar
later in the talk. apple rust. We'll see more of that, again,
We deal with herbaceous plants, both outdoors, things like hostas and phlox and those sorts
of plants.
We also deal with indoor plants. Although, quite frankly, that's a very small proportion of the
plants that we deal with. We also have a very thriving
specialty crop industry in the state.
I have a lot of experience
working with ginseng. In my previous job here on campus I was basically the
program manager for the Ginseng Research Program. So we do a lot of ginseng, and
the expert in that particular area on campus. And then more recently we've so I'm still kind of considered
assays. There are certain pathogens that started doing a lot of soil
for nematodes, which are small you can actually extract from soil, and we do a lot of tests
parasitic worms that can be quite detrimental to particularly a lot of our field
crops, soybeans in particular.
We do some tests for soil-born fungi or fungi-like pathogens that can cause problems in
alfalfa and also in peas. We'll talk about that.
So we do a wide range of testing on a wide range of crops.
About the only thing you
probably don't see up there, what don't you see up there?
We don't do turf. And that's because we have a Turf.
special lab that deals with turf diagnostics.
It's run by Paul Koch who is a
staff member in the Department of Plant Pathology under the
our turf pathologist. What else does the PDDC do? When I'm not looking at plant samples, I'm doing lots and lots
and lots and lots and lots of outreach. I do about 70 talks a year. And sometimes it's a field day,
sometimes it's a talk like this.
I do a lot of teleconferences. Somebody who came in said they'd
I do the Larry Meiller show, heard me on the radio.
Garden Talk, every once in a while.
month a radio show in Milwaukee that's no longer on the air, but I also used to do about every
we did that for eight years, a group of us in UW Extension.
And that was a lot of fun.
I do television programs with Shelley Ryan.
She's really lots of fun. We have a lot of fun. Last time we did a shoot we were She's a hoot to work with.
Disease and ended up shooting in doing something on Dutch Elm
working with her. The other thing that I do quite a bit of is writing. So that's always enjoyable
informational sorts of We try to do a lot of
was a big call amongst the publications for our clientele. In particular, when I first started with UW Extension there
Easy to use fact sheets for horticuhomeowners.s in UW And so as a team we came up with very, what do I want to say?
University of Wisconsin Garden these publications called the
Facts. And we have about 200 tittles in
diseases, insects, general that series now that cover
in terms of writing a fair horticulture and a variety of different topics. And I've been involved in that
number of those and also I serve as the editor for that
So that's something that keeps particular series.
me busy in the wintertime. So it's really about figuring out diseases and trying to
provide that information to the general public in whatever
manner really works. Who does the PDDC serve?
Again, pretty much anyone.
We have, what, about five and a half million people in the state.
Personally, I consider every one
of those people one of my clients. So if you live in the state of
Wisconsin, you can send me a
very careful to make everyone aware of this, that if there is Wsomeone who cannot afford a, bdiagnosis who really needs it,
we'll do the sample for free. And actually we've done a lot of
free sampling recently with late blight, again a disease we'll
talk about a little bit later.
We decided to offer testing for that particular disease free of tomatoes pacharge.rly in 2009 So it was a disease that had
huge impact for the potato
industry in the state and also our fresh market tomato industry
do that free of charge. We also do free diagnostics on and we decided that we needed to
diseases that we call regulatory diseases.
And I'll describe some of those a little bit later as well. Kind of the commodity or the
the center here the county groups that we serve, again, in
extension agents really are technically my primary clientele, but we also will
serve what I call primary producers.
a problem. So anyone who is actually growing the plant that's having
It can include people in the So that can include farmers who are growing things like, again, corn and soybeans.
horticultural industries like greenhouse growers who are growing crops like geraniums or
other types of bedding plants.
It could be someone in a nursery growing trees or shrubs.
Also included in that group in Those are all primary producers.
the upper right-hand corner, a lovely picture of some nicely diseased phlox, homeowners.
Homeowners are a big group that bring in a lot of samples to my clinic. Because I'm located, my clinic
is located in Madison, we have a
lot of folks in the Madison area who are avid gardeners who are
diseases are. They tend to be able to pay for the service so they're willing very interested in knowing what
get a lot of walk-in clientele. And we do have a walk-in service to bring in a sample, and so we
as well are what I call consultants. through our clinic. The other group that we help out
In particular, I have a lot of interaction with the arborists
in the state, the Wisconsin Arborists Association.
I give talks for them, but they provide a lot of samples for my And I've rouclinic.visited with We do a lot of trees and shrubs.
In fact, until recently about 80% of my sample that is came into the clinic were ornamental samples, either trees, shrubs or
herbaceous ornamentals. So we do a lot of samples that
are really not productions crops, per se, but just plants
that make people's lives better by making the environment more
beautiful. But we do have other folks in
that kind of consultant area. A lot of crop consultants as
group as well. well. And I do some training for that
state where we basically train I do some sessions called IPM Scout School. Three different locations in the
crop consultants on how to identify diseases of field and
How do we do it? forage crops.
How does the PDDC do what it does? Well, here is what I would like
to say is what happens in my
the diagnosis. clinic. A symptomatic plant comes in. I have an epiphany and there's
And we have a fact sheet we pull off our wall and then we're done
please pay me my $20 for this sample. That's not exactly what happens. and I put out my hand and say
take my hat off, there's not As you can kind of tell if I
much hair up here anymore and that's because typically the process looks more like this.
[LAUGHTER]
Kind of a ran/walk sort of process where we're going all over the map trying to figure
out where things are. We certainly do get some of the samples where it's, I look at it, I know what it is, we're
done. I call them the easy money
samples. And they're nice when they come
in. But, quite frankly, we don't see
first started in the clinic 13 a lot of those anymore. Saw a lot more of those when I
years ago, and I'm hoping that part of the reason why I don't
much as I love them, is because we've done a good job educating the public on what these easy to see those anymore in the clinic,
what needs to be done with them. identify diseases look like and
And I think we do spend a lot of time trying to train the general
gardeners and also to train our county extension agents so that they can recognize these public, to train master
to send them in to the clinic for a formal diagnosis. On the other hand, what has dhappened is the samples that Ie
get nowadays are a lot harder to
they're more challenging for me, do than when I started. They're more complex, they take a lot more time, and in a sense
and I have to say that when I've been working with a really tough
what it is, it's very, very satisfying. And it's really nice to have sample we finally figure out
job after 13 years. So I am grateful that I see a variety of things and do see new those sorts of challenges in a
really keeps me on my toes and things all the time because it
it makes the job very, very interesting. I really do love my job.
I think I have one of the coolest jobs on campus, quite frankly.
sort of thing. So I do enjoy doing all this
What else? How else can we talk about what I do?
Well, I would not be a plant
pathologist if I did not put a slide of the disease triangle in
And this is kind of the basis on my talk.
which we talk about diseases when try to teach our students
and how to manage that disease. And what the plant disease about what a plant disease is
summarizes the three important triangle does, or the disease triangle, it basically
components to a plant disease. You need to have a susceptible
come down with a particular disease. host that's a plant that can
microorganism that can cause the You need to have a pathogen which is some sort of
disease. And we'll talk a little bit about what those are in just a
second. And then another very important component of a disease is a favorable environment that
allows the plant, the susceptible plant and the pathogen to interact. And this is a process that
occurs over time. What we see as a manifestation
seeing is what we call symptoms. of that interaction is disease. And usually what we're really
So some abnormality in the plant that gives us a clue that something's going on that isn't
quite right.
try to figure out the various components in the triangle so that I can provide management identify winformation.ase is but
How to control the disease. And really when you're trying to
control the disease, what you're trying to do is trying to
eliminate or at least reduce the
importance of one or more of the corners on this triangle. You're trying to modify the
environment in some way so the
disease is less likely to develop, you're trying to make a recommendation to grow something
else other than the susceptible host that's having the problem
or you're trying to figure out ways to get rid of the pathogen
or at least reduce the amount of
infections. And so that's kind of the basis of this sort of information that you don't see as many
Now I don't, in my reports to my we're providing.
clients I don't put it in the context of the disease triangle. We just kind of tell them what
they need to do.
Grow a different plant. We'll tell you which ones we think are appropriate.
Thin your garden to modify the
environment. That will help. Or, at this time of the year,
one of my big recommendations is
get out there and do good fall clean up because all of those disease causing organisms are
surviving, or at least many of
that plant that has died back them, inover the summer.debris. Those leaves that have fallen off your tree are the remains of
So again, that's part of what we look at when we're trying to
figure out what's going on. One of the things we do is
information on all three of the corners of the disease triangle. collect a lot of information. We have to kind of collect
The bane of my existence, I have to say, from the susceptible
host point of view are a lot of the new varieties, epitomized by
that have been bred over time for yellow foliage. I can't tell you how much I hate left photograph on this slide,
they arrive at my clinic yellow foliage varieties because
oftentimes just saying this is an arborvitae, and my first thought is boy is that diseased.
[LAUGHTER]
And then I have to step back and say, wait a minute, call up the person who submitted it
and say, do you happen to know
which variety this is? And then they tell you it's something like Golden Glow
Arborvitae, or some such. That's probably not a real
variety name, but once you get a sense that it's been bred for
that then it makes your life a
lot easier. But it really points out the fact that you really have to
know what a healthy plant looks like of that particular variety of plant in order to really assess whether it's diseased or
not.
But it really does make it a challenge with some of the newer
And quite frankly, I go out shopping and I have to say, my varieties that have been bred.
buying experience is a chance to friends hate me when I go shopping because every plant
see diseased plants quite frankly. And I've seen hosta varieties
that are being sold as varieties
that are swear are infected with viruses.
of a viral infected plant they've been released as a true variety. And they just have the symptoms
that certain types of plants we actually want them infected with And you have to keep in mind
particular disease causing organisms.
Anybody like poinsettias? You like poinsettias? You know what a native
wild? It's a tree. poinsettia looks like out in the
It's a tree. And actually those plants are
infected with a type of pathogen
called a phytoplasma. It gets in the phloem of the plants and causes the plants to
stunt and bush, and that's why
we get our lovely, really bushy, lovely looking poinsettias. And actually, Shelley Ryan and I
did a lovely little segment on
when bad pathogens went good and how pathogens can actually help in our lives.
But, again, knowing what a
healthy plant looks like or what a "normal" plant looks like is
Other sorts of information that we collect, we spend a lot of time asking about patterns of very, vdisease.rtant.
Particularly, if you're dealing with some sort of field crop, I want to know how the disease is distributed in the plant.
Is it uniform?
I told them I would genuflect quite a bit. Is it uniform in the field?
Is it patchy? Are there really sharp
And in kind of this middle top delimitation between diseased and healthy tissue?
photo you can see an alfalfa field where there's a very
the field, and that sort of very distinct line down the middle of
probably some human component in sharp junction between diseased and healthy tissue really gives you a sense that there's
what's going on here. And it's these sorts of patterns that we look for.
And in that particular case what
and the half on the right they the grower had done is they planted a companion crop with the alfalfa, they planted oats,
harvested very early, they basically cut it back as kind of
they let it grow to a fair size. a green manure, and on the left
And that basically modified the environment and made it much wetter on the left side of the
field, and that was very
favorable for disease to develop.
the bottom two slides with the Other things that we look for,
sometimes we have things other arrow, we look for temporal patterns, how the disease changes over time, because
than disease that are going on. There are certain types of physical damages, insect damage,
those sorts of things that
aren't true diseases that can happen in a field, and oftentimes that sort of damage
tends to arrive fairly quickly
but it never progresses. It never gets worse.
With diseases they usually get It kind of stays the same.
worse over time, particularly if we have a lot of wet weather. Water is a real driving factor
in a lot of diseases. And you can kind of tell that from the slide in the upper right.
Sorts of environmental
of time we want to know about crainfall, drought, flooding, a get information on. Certainly temperature but lots
lot of information about water because a lot of the organisms
that I'm dealing with very much require substantial amounts of
little bit later. But all of these sorts of types of information are important. We also get information on soil
type, topography, fertility,
just a wide range of information because the more information
do at giving a good specific that we have the better we can
diagnosis on why a particular plant is having a particular problem.
What else do we do? Well, once we get samples in the
And that usually involves doing some sort of macroscopic sort of clinic we initially kind of triage them.
examination. We're going to look at the plant
by eye to see whether we can get
a brief or write a brief description of what we're seeing
And what we look for are that's going wrong.
different types of symptoms that usually fall into five different
This lovely squash in the upper left has a lovely rot symptom. categories.
basically a degradation of That's one of the major groups. It's called necrosis so
tissue. And there are all kinds of different types of rots.
All kinds of different plant
parts can rot. Fruits can rot. Roots can rot.
Crowns can rot. Pretty much anything on a plant will rot under the right
We look at kind of whether conditions.
If it's really slimy and they're dry rots, which tend to be more typically fungal in nature, versus wet rots.
disgusting, it's probably a bacterial rot. Although that's not always the
case. Sometimes fungi come in and initially cause the problem, and
causing bacteria that will then there are other non-disease
follow and basically finish off the job. But they wouldn't cause any
problem on their own. It's just because something else
came in first. But we have to kind of tease
that sort of information out of the sample and sometimes we can tell a lot just by looking at the sample visually.
We also look for discolorations.
An example in the upper center photograph. A rose with these lovely yellow
line patterns.
yellowing, sometimes a general And sometimes it's not this distinct. Sometimes it's just a general
problem in the plant. Purpling can be a phosphorus General yellowing is oftentimes an indication of a nitrogen
this rose oftentimes are an indication of a viral infection. deficiency. Line patterns like you see in
different types of symptoms you can really, again, get a lot of clues about what might be going on just looking at symptoms by
eye.
We also look for what are called overgrowth symptoms.
cancerous growths on plants. So galls, swellings, big kind of
And this is my favorite of the overgrowth symptoms.
on a stick because that's what I call this affectionately poop
it looks like. It's a disease called black knot.
It's specific to cherries and plums, anything in the genus
Prunus, quite frankly. And it looks like an animal has
defecated on the branch.
It's very distinctive. It is one of my easy money
can look at the symptoms on that diseases by the way because I
And sometimes I recommend what and I know exactly what is it and what to tell a client to do which is basically prune.
we call basal pruning which is one single prune at the ground
[LAUGHTER] level.
about an elderly woman and a We can come back to that. I can tell you probably my most embarrassing story in the clinic
We'll come to that maybe a tree that was a memorial to her dead husband and me sticking my foot in my mouth.
little bit later. Other things that we look for: undergrowth symptoms.
So where plants or plant parts
are smaller than normal. You can see this, this is actually a soybean field in the
lower center here.
It actually has a lovely combination of symptoms, if you want to talk about several
things that you could look for. One of the things that you can
the center, and it's kind of in a nice big round patch. That's important to notice that, of yellowing in those plants in
actually concentrated. that it's not uniform, it's
There's yellowing and then the other thing you notice is where those plants are yellow you can
actually see between the plants you can see the soil between the
entirely closed. plants where the greener plants in the foreground the canopy is
So there's a lot of stunting going on in those yellow plants that are smaller than normal.
So we've got stunting.
We've got a patch and we've got yellowing. The yellowing is probably
due a nitrogen deficiency.
and that probably means that These are soybeans which should nodulate, so they should be producing nitrogen on their own
there's something going on in the root system that's interfering with water and
nutrient uptake and nodulation
of the plant, in this particular case a nematode pathogen called soybean cyst nematode.
And I'll show you that one in a bit as well.
The other major group of symptoms are the wilt symptoms
where the plants just get droopy. They can't get enough water.
different types of disease And there are a variety of
causing organisms that can cause that sort of symptom. Now at my house when I see
wilted plants like this it is not a disease problem.
It is a drought stress problem because I use what's called the
wilt test for watering my house plants. If the plants are wilted, they
Now, that's not a great way to must need water.
treat your plants, but I run little experiments on my house
they will survive without water. plants at home to see how long
Some for several months, quite frankly.
when they see a plant like that, Unfortunately, for most people
what's your reaction? You water it, right? And if it doesn't recover what
do you do?
kind. And you know what you've done? And usually the problem at that point is a root rot of some
disease triangle? You've made that really big. Remember that favorable environment corner of the
You've made the root rot pathogens really, really happy
by providing all that water.
So, again, looking at those symptoms, getting a sense of whether the soil is dry versus
wet, again, gives you a sense about what might be going on. So, again, types of symptoms: necrotic symptoms, discoloration
symptoms, overgrowth symptoms,
undergrowth symptoms and wilting.
You're basically getting our Those are the five major groups.
introductory plant pathology course tonight in one hour. It usually runs 18 weeks.
The other thing we look for are what are called macroscopic signs.
That's an odd looking plant, We talked about symptoms.
some way in which the plant looks weird. When we're talking about signs,
what we're looking for are
organisms that are causing the actually pathogen structures or the pathogens themselves. We're actually seeing the
disease. And, quite frankly, a lot of
the middle top you see a lot of white on that African violet times what we're looking for, in
flower, that's actually a fungus growing on the surface of the
flower. It's a powdery mildew fungus. You're primarily seeing fungal
a microscope slide of that in just a second, and a lot of spores. tAnd these are the reproductiveu
structures of this particular fungus. And we do spend a lot of time looking for spores because
that's a major thing that we
need to see in order to identify most fungal pathogens.
the upper left there are a group On the upper right and also on
of pathogens called the rust pathogens which oftentimes
and very visible spore masses on produce very, very distinctive
plants. Usually what you'll see if you're looking in a home garden,
it will look very similar to
actually if you rub against them what you're seeing in the upper right where you have these very bright orange spots that you can
you'll rub off an orange powder. And those, again, are spores of this rust fungus.
Very, very cool organisms.
over again, I'd either probably Istudy rusts or powdery mildews back to graduate school and decided to do plant pathology
And we see a lot of them in the environment. because I think they're really, really cool fungi.
the soybean seed in the lower left, you see all these little Other sorts of things that we look for, if you take a look at
droppings, those are actually fungal structures. black things that look like mouse droppings or rat
They're called sclerotia and it's a resting structure of a
fungus that causes a serious
problem in soybeans. The disease is called white mold, and these little
structures sit around on the
ground. They can stick around for on the order of five to seven years in
the soil, and they germinate in the spring. And in the middle slide you can see these little tiny things
that look like little mini
mushrooms, and that's what are produced out of these black mouse dropping-like structures,
and those are what produce the
spores for this particular fungus. Another famous disease that also
produces these sclerotia is something called ergot. You've probably heard of the
Have you ever heard of Salem witch trials.
thought to be a connection St. Anthony's fire? You may have heard of that. Both of those are, there's
between ergot and both of those. Ergot is a fungal disease that
Rye is a very susceptible host. Back in the middle ages, rye was occurs on small grains.
And oftentimes it was infected the primary grain crop that was used to produce bread in Europe.
crazy chemical compounds. Many of them closely related to sclerotia, thoLSD.ittle resting structures produce all kinds of
with the grain, ground up in And they would get harvested
flour and back baked in bread. And these compounds would not break down in the heat of baking
and people would eat this and basically have all kinds of hallucinations. They would have problems with
circulation.
It basically really fouls up pretty much most of your body and at high enough concentration
will kill you.
And it's thought that the Salem witch trials were also associated with ergotism, so
eating ergot, and they think
that some of the women that were accusing other people of being
hallucinating because they will get a hold of some of these compounds in bread. So very interesting disease.
There's a lot of interest in
this particular disease nowadays actually in medicine. You can take some of these
particular products, distill
them and at the right concentration they can be used medically.
In particular, they can be used to induce labor during
pregnancy. What else do we look for?
Well, once I've looked at the plants at kind of a macroscopic level, next thing is to start looking at the tissue under a
microscope. And I spend a lot of time at the
ergonomic chairs, so I don't microscope. We finally got some really nice
have back problems anymore. That's very important as I get older.
And the sorts of things that we look for, in the upper right
we really spend a lot of time looking at what fungi look like. hand corner I talked about this term hyphae or fungal threads,
This is how they grow during their non-reproductive stages.
And depending upon the
particular fungus that I'm looking at I can identify it
like. There are very few fungi where I based on what the hyphae look
The one on the upper left here can do that but there are certain ones that I can.
where it branches. is a fungus called rhizoctonia, nasty little root rot pathogen, but it forms T-shaped cells
And that's very diagnostic for that particular fungus. We also look for reproductive
structures, lower left. In this particular case, one of the reason I love powdery mildews is because of their
sexual reproductive structures
That photograph is at least 400 that atimes normal size. this time of the year. They're incredibly ornate.
that are coming out. And look at all the ornamentation, those little arms
They look like antlers. We have a new powdery mildew that showed up in the state
about five years ago. It's a European variety.
It occurs on maples. Those little, they're called
appendages, those little arms,
they come out and they look like tuning forks that do little curly Qs on the end.
So this beautiful, beautiful
structure producing lots and lots of spores that can cause lots and lots of disease
problems. The other thing that we look for
sometimes are nematodes, lower right.
And these are worm-like organisms that we find in soil, and I actually spend lots of
counting these. I have what's basically a white blood cell counter that I have time at the microscope actually
clicking away. sitting next to me and I'm just
I think I drive my technician, Ann Joy, crazy because click, click, click and when I get a
hundred there's a ding. So she's very patient with me when I do that. Upper left we also look for
bacteria. Not a great way to identify exactly which disease you're
us a sense of whether there may be a bacterial pathogen present. looking at but certainly gives
It has kind of a watery sort of look to it. WThat's the macroscopic symptom decayed tissue on leaves.
Then we'll take a little bit of tissue at the edge of that that we look for.
between the diseased and healthy tissue, put it on a microscope
slide in a drop of water, slice across it with a razor blade and
then we look at that cut surface.
And if there are bacteria there,
you can see all the granule material in the upper right in that slide, those are all
bacterial cells just oozing out.
It looks like the Nile Delta, quite frankly, coming out of the plant tissue.
And once we see that then we'll go on and do other techniques to
try to get a better sense of which bacterium we're dealing
with. And that kind of comes down to
the next thing that we do with our samples which is basically
we do a series of techniques
isolation techniques where we're where we either incubate tissue under high moisture or we can also do certain types of
trying to coax the disease causing organism to grow out of the tissue so that we can
identify it on particular types of growth media that we have. When we're talking about
we call moist chambers, we incubations, we use either what
oftentimes do these are petri plates lined with a little bit of filter paper that's wet,
stick a leaf on that wet surface
and let it sit for two our three days and if there is some sort
will produce spores in that time of fungal pathogen there, it
and then we can look at those spores under the microscope to identify what we're seeing.
We also do what are called humid
Potato leaves are particularly chambers. Sometimes we leaf tissue that's very, very delicate.
problematic. If we put it in contact with wet
disintegrate. So what we do is we put wet filter paper on the bottom of plastic bags, some dry petri
plates on top and then kind of
lay the tissue over the top, and we just create a nice humid environment and we can look for
different types of pathogens in that more delicate tissue without as many problems with the tissue just kind of
disintegrating over the three-day period. We do isolate bacteria, that's
We have a couple of workhorse media that we use. shown in the upper right.
carbonate medium which is shown here. It is a very white color. There's a particular bacterial
pathogen called Xanthomonas, and
if that particular organism is present we get these lovely very
colonies. They're very easy to identify. mucoid, so kind of slimy, yellow
We also have some fungal media that we use.
One is potato dextrose agar, so it's got basically boiled potatoes that have been strained, a little bit of sugar
dextrose and then some agar to
solidify it. And we use that as our workhorse
And this particular organisms, for most fungal pathogens.
We'll talk a little bit more that lovely buff color, that you're seeing, that's the pathogen.
about that disease in just a few minutes.
We can also do soil assays, as I So, that's one step that we do.
mentioned before. We do a fair amount of that. The ones that we really
concentrate on, we do a lot of
soybean cyst nematode testing, and that involves taking a soil sample from a soybean field and
we actually sieve it through a
solution, sucrose. very fine sieve and then we place some of the material in a very thick syrupy sugar
So right off we actually buy sugar at the grocery store for
And you basically put it in a centrifuge, and these what are this.
called cysts will actually float out on the top of this material.
And these cysts, what they
basically are female nematodes that have filled with eggs.
So this particular nematode,
when the female lays eggs she lays them internally, her body swells up like a bag, originally
she's white in color but then she dies and the bag, this cyst turns brown.
soil. And then what I have to do is crush those open to release any Andof the eggs or juvenile in
nematodes that are inside and I get to count those. And the one that I did, I didn't
eventually when we did the math calculation back it was about 5,000 nematodes per hundred CCs actuallyof soil.,000 but
And we've had as many as close
soybean production. tYou can get probably a 50 or that's a huge number that can really significantly impact
We also do what are called bait techniques. This is a very general test it's a situation like that.
types of root rot pathogens. designed to look for certain
Take a soil sample and you float or you pour over that soil a one
distilled water and, to one mixture of sterilized
interestingly, filtered sterilized Lake Mendota water. I swear what's the protocol
says. That's how it was developed.
down in the lake, I'm not getting a tan, I am there So collecting water for this on one oparticular assay.my arm
And then what you do is you take
and harvest leaves, cut little little bits of citrus leaf, and we actually keep a plant at one of our greenhouses so we can go
squares out of the leaves, float it on the surface of this water and after a certain period of
time we can come back and look
for structures that are characteristic of these root rot pathogens that is have started
to grow in the citrus leaf
pieces. The other big money makers for the clinic, soybean cyst
nematode actually we make a fair
amount of money. We've probably made $6,000 or $7,000 on doing those samples.
That's $22 a sample.
We actually do that particular testing in cooperation with Shawn Conley in our Department
of Agronomy.
He gets a grant from the Wisconsin Soybean Marketing Board to actually, we're
actually able to do up to a thousand nematode samples a year
at $22 a sample. The other, our most expensive
test that we do is the one in the upper right which is a soil assay.
intensive. It's $150 and it's very labor
alfalfa in that soil that have We actually get a soil sample from an alfalfa field, we plant five different varieties of
resistance to different types of pathogens and then we basically do a stand count, we flood the
soil, we watch the plants die and then we basically, every
plant, and we do about 90 plants per one of those little plastic
squares, every plant we rate or evaluate the root system for
disease. I can't remember if that one is
a one to five or zero to four,
but in any event there's a scale that we use for healthy to dead,
analysis to basically see whether there are statistical differences between the different varieties, and based
on those differences we can make
a recommendation of what sort of resistant variety a grower
The other test that we do, should use.
again, that we make a fair amount of money, I inherited
Bob Rand and his former major professor, Don Hagedorn, this test from a colleague,
inherited that. It's a pea root rot test. And actually this is an exciting tested for years, and I've
information from the canning test because I actually can get
companies on how valuable this test is to them.
contract with growers to grow peas in a particular field, but they don't want to grow in a What they do is they want to
likelihood of pea root rot. So they'll bring us a sample, we field where there's a high
once they are about seven days pot it up, we plant peas in it, we let the peas germinate, and
old then we start flooding the soil with water.
very moist, and then we allow the plants to grow for an additional three weeks, and after a month we harvest all the
plants and we evaluate again the
root systems. And it's one of the most gratifying tests that I do
because you can actually see the
differences as the plants are growing in the greenhouse. We have positive controls which
are soil where we know there are
lots of root rot pathogens. Those plants are dead as a door nail.
We have a negative control where
we do it in a sterilized potting mix.
very healthy looking. And then if you look at the test The plants are usually huge and
And we kind of divide the different types of soils into three different groups, either between.
And the economic data that we've good, bad, or uncertain.
gotten from the canning company is that if we can identify a bad field and they instead of
planting in this bad field
planted it in one of good fields, they can actually double the gross profit per acre.
So it actually can save them
hundreds of thousands of dollars every year. So it's a very gratifying test
for a variety of reasons. But we do spend a lot of time doing these sorts of tests. Pea root rot is a winter
activity. I usually do that in December and January, and it's lovely in Wisconsin to be inside a
greenhouse in the middle of the winter where it's warm and sunny
and really lovely around green and growing plants until, of
course, I kill them off.
We also use a lot of serological techniques. There's a company in Elkhart,
Indiana, called Agdia Inc, and
they have basically specialized in the diagnostic field in developing serological
techniques, particularly for
testing for viruses, but they also test for a variety of other types of pathogens as well.
And they've come up with what are basically the equivalent of a home pregnancy test for pathogens.
It's a dip stick test.
You take a little bit of tissue. You put it in a plastic bag that
that will help grind up, and has some rough material inside
the plant sap and some buffer that's kind of a water/mineral stick that you put in the solution, it's a combination of
material is sucked up by solution. That's in the bag and the
capillary action that's in the test strip. And if you get one little pink
line, it's a negative result. If you get two pink lines, it's positive. These are very specific tests so
usually you're testing for a
single virus or a single pathogen. They are very, very useful and
they're fairly inexpensive. In fact, I oftentimes recommend those sorts of tests for
oftentimes have a lot of virus greenhouse growers who
problems. So for about $5 a test you can get a good sense of whether
you've got a virus problem. We do more kind of conventional serological techniques, like
That's shown in the far right. ELISA.
And we can do that to test for a large number of samples all at
Oftentimes we don't do a lot of that. We tend to go with the test strips if we can.
Traditionally, it tends to be a little more expensive than our
clientele is willing to pay for. There are certain tests where we
can use this. There's a potato disease called bacterial ring rot, is of regulatory concern here in the
state and it's one of those diseases that if you are a seed potato producer, you never want to see this particular disease
in your field because you will
be banned from growing seed potatoes for, how long is it Bob?
Is it 10 years? >> I don't recall.
>> Five to 10. That's a long, long time.
So it's a very destructive
And we occasionally have to use pconventional ELISA to test for see if you're a seed potato producer.
techniques, particularly that. We also use some DNA-based
polymerase chain reaction, or PCR. This is a technique where you
can look for particular stretches of genetic material of
a pathogen that are specific for that pathogen.
You basically make lots and lots
And we do some of that. of cAgain, it's usually tooific expensive for us to really do on visualize it using a dye.
clientele, but we do offer a routine basis for most
certain tests in that arena. And more recently we've actually
We had a new pathogen for Wisconsin show up in the state gotten into DNA sequencing.
this past summer on wheat. It's a fungus called
Cephalosporium, and we actually sequenced that particular organism to verify that it was
thought it was. So we do do all these sorts of actually the pathogen that we
do once we've kind of decided which tests we're going to do, techniques. And then what really we need to
observations, we've got all the other information that we've we've got our macroscopic observations, microscopic
a conclusion about what's going on. And as an example, one of the very common diseases that I see,
we'll get complaints from a client that they have an
Austrian pine that looks really, really unhealthy.
A lot of brown branches, brown
needles, just looks horrible. If you ever want to see a tree of this type, you can come over
to my lab.
I'll take you right outside. We have Austrian pine that has
I'm hoping that grounds doesn't cut it down because it's a great this particular disease.
teaching tool but they may eventually.
But if we see this sort of kind of symptom at the landscape level then what I start looking at are the individual branch
tips, and if I see a lot of uneven lengths in the needles with some sap production in that
those needles out and I look for branch tip, then I start pulling
these little structures on the far right.
the Hershey's Kisses of death. One of my colleagues calls these
[LAUGHTER] And that's Denise Smith, who
pathologist Glen Stanosz. I love that. works with our forest
But they do look like little brown Hershey's Kisses that pop
up through the base of the
will pop those lovely little needles, and I pluck those off, put them on a microscope slide, squish them to death and out
What I hate are getting little large brown spores. And I love spores that are big. I love spores that are colored.
It's very difficult to identify. tiny colorless elongated spores because there are tons of fungi that produce those.
Diplodia, and particularly if we But when you have something big and obvious like this we know that it's a fungus called
clue that we're dealing with started to see these symptoms during a period where there's a lot of drought, that's another
this Diplodia. This is a disease that tends to be more prevalent on drought
stressed trees. And definitely seeing the fungus
But all this information is very, very important as I am, again, still putting it together give away.
And pretty much every client and reporting back to my client.
gets a customized letter/report. I spend a lot of time writing letters.
Sometimes late into the night at
another letter again I would be very, very happy, but it's one And sometimes it's to the point where if I never have to write
of the things I've really, really emphasized when I started
in the clinic.
I figure if people are paying me to do a diagnosis, they need
shows that I've done my job. something in their hand that
And what we do is we try to provide as much information as possible on the disease and how
to control it.
What I found very early on was that I didn't like writing two- or three-page letters to
describe all of the things
Wisconsin Garden Facts because people needed to do, and that was part of the impetus for developing these University of
then my letters become very short. Here's what we did, here's what
we saw, this is the disease,
here's a lovely fact sheet for you to read about it, if you
So that's what we do in the clinic. And we do a lot of it. have questions, contact me.
very interesting year because our sample numbers are way, way down. I think we're really seeing the
effect of the economy.
People don't want to spend $20 or $25 to have a diagnosis. We're probably going to be down
about 30% over last year. Normally we've averaged, over the 10 years or 13 years that I've been in the clinic, about
1700-1800 samples per year. And this year we'll probably end
up, my estimate is around 1100 or 1200, somewhere in that area.
But it doesn't seem like it's been less busy in the clinic. We've gotten a lot more requests
People like to send me digital via email.
photos, which I love to see if they're in conjunction with a real plant sample.
I can't do a lot of diagnosis specifically off of photos, unfortunately.
I'm looking for is microscopic. So certain things like black Primarily because a lot of what
knot, that poop on a stick, that one I can do from a photo, but
if it's a lot of other diseases,
I really can't tell much from just a photograph. But I love to see those
photographs, particularly landscape shots, because
landscape that gives me that oftentimes if I can see how a plant is situated in the
ancillary information so I can write a very specific report and
information to a client once I provide very specific control
do know what the disease is. Or if I find out that it doesn't
happens a lot, if people don't look like a disease, that
provide me with that ancillary information, they get a two-page
I call it my litany letter which letter from me.
usually trees, might have gone basically I try to list everything I can think that might possibly gone wrong, it's
wrong with that tree that may have caused, usually it's branch dieback, unfortunately.
Their branches die, they send me
the branches, it's not a branch problem. If I've got landscape shots,
sometimes I can see things like girdling roots or trees that are
poorly planted, and then I can comment specifically on that in
the report. But we do try to be at specific as we possibly can. Our policy for charging is you
send in a sample the first time,
we may request a follow-up sample. If we've charged you $25 the
first time around, we won't charge you anymore for a
follow-up. If you send in a sample that was
a $20 charge to begin with, the follow-up would have cost you the extra $5, we'll charge you
but you pretty much max out at the $5 the second time around
And hopefully this will answer $25 per sample. So what sort of diseases that I see?
some of the questions for the people that said they had some disease problems in their yards.
We see a lot of common diseases,
and a lot of these fall into the category I call the easy money
These are ones that I can pretty diseases.
much look at and tell you what they are. We talked a little bit about
powdery mildews.
powdery mildew on zinnia which We see that on all kinds of different plants. This particular photograph is a
is probably one of the problematic hosts amongst the annuals.
Phlox and bee balm are another
great host for this where it can cause a lot of damage.
primarily a cosmetic disease, but if you grow ninebark, particularly diabolo ninebark, On woody ornamentals it's
so severe that it will cause we can get powdery mildew that's
Another fun disease to diagnose because it's so easy and And that's very unusual for powdery mildew.
actually quite pretty is something called golden canker.
The official name is
Cryptodiaporthe canker, named after the fungus that causes the disease.
Plant pathologists can be very
cruel. They do like to use Latin names as part of the common names, and
I prefer golden canker. It's more descriptive.
It's specific to pagoda dogwood. Usually occurs on trees that are
planted in the wrong location.
Lovely trees but because they're People love pagoda, those are the ones are the really kind of horizontal branches.
so pretty they want them right in the middle of their yard where everybody can see them.
So they're usually surrounded by
grass and in direct sun. These are understory trees that like cool temperatures, and they
like a lot of moisture. And if you've got turf growing
up around them that tends to stress them for water, and when
the trees become stressed this
Yeah, I hate roses. golden cankI'm sorry. comes in. How many people like roses? People like roses?
I really am. It's another plant that hurts me
when I work with it so that's the reason I don't like them. But I know people, if they like roses, they're usually really
rabid about liking roses. And the bane of probably every
These roughly circular black rose grower's existence is black spot.
spots, kind of fringy edges, will eventually cause defoliation, particularly older
varieties that have not been
bred for resistance. But a lot of the newer varieties
breeding program to breed for very high levels of resistance have gone through an extensive
to this disease. So newer varieties tend to be
very good.
We don't see a lot of disease but the older more traditional varieties will see a lot of
problems with this, particularly
if it's a fungal disease. Fun disease I talked about before, cedar apple rust.
This is a disease that actually is a rust that has two different
hosts. There are rusts that spend their
entire life cycle on a single plant.
This particular one actually bounces back and forth between
two hosts.
This is what you typically see in mid-May to mid-June. If you ever see these, I think,
beautiful, slimy orange marmalady masses, sometimes they
other types of junipers. look like orange little octopuses on your red cedars or
they're not reinfecting the Thajunipers or the red cedar,e. And the spores that are being produced in that orange mass,
things like apples, crab apples, they're actually infecting an alternative host which include
quince and hawthorn. If you're on campus and want to see the alternate phase for
this, go over to Slichter Hall
where the Allen Centennial Garden is.
know where that is. Right across Babcock Drive If you're a gardener, you should
there's beautiful hawthorns that are just loaded with the
alternate phase of cedar apple
rust. One of the best stories I've ever heard, it made me laugh
harder than I think I've laughed
in a long, long time, Karen Lawrence who is the former head of grounds here on campus,
said that a student came up to her one time, mid-May, the student's comment was,
because that's when the red cedars bloom. [LAUGHTER] I love this time of year,
cedar apple rust galls. [LAUGHTER] And what she was seeing was
So we talked about poop on a stick and the control
for that. Pruning, oftentimes basal pruning.
you're seeing on there, that's And actually the white that
So it's not the organism that's accausing the disease, it's aus thsecondary organism.he And then the number one disease
that I saw this year on any crop
was the one on the lower right. That's Rhizosphaera needle cast. If you went around anywhere in
the state, you probably saw a lot of spruces that were losing a lot of needles. And particularly if it was
interior needle loss, so near the trunk out, it was probably
frankly it probably wasn't this disease. Very, very common and quite
anything that happened this year so much as our wet springs in 2009 and 2010 that really
contributed to us seeing a lot
of this disease in 2011. Those wet conditions really set up the trees to have a large
number of infections, and with a
needle loss from this disease. little bit of heat stress and water stress that we had this year we really saw a lot of
So these are diseases that I like to see in the clinic because they're easy for me to
do, particularly after I've had a challenging hard sample it's
nice to have something like this to come back to where I feel
really good that I've made a
quick diagnosis. Sometimes we have diseases that get a lot of press that we will
diagnose in the clinic. Usually pretty much every year
somewhere in the state we're going to have some press on oak
wilt. It's a very, very important disease.
state. We have a lot of oaks in this
vascular wilts. ThAnd those include oak wilts,d of a representative disease for a group of diseases called the
Dutch elm disease, which I'm sure nobody's ever heard of, and
also another disease called verticillium wilt, which is kind
damage to oaks. The pathogen actually enters of one of my favorites. But oak wilt causes a lot of
introduced to an area it's into the tree through wounds. At least when it's initially
brought in by sap beetles that have spores of the fungus on
to feed on the sap in a wound, their bodies, and they come in
drop off the fungus, the fungus infects the water conducting tissue and leads to blockage of
that tissue, and that leads to
called the red oak group, those tare the oaks with the pointedt lobes, those particular trees Pacan die within one growing's
season from this particular disease.
very, very similarly. Verticillium wilt is a little different because that fungus is verticillium wilt both function
enters through the roots. But the wilting sort of symptoms a soil born pathogen and then
that you see are very typical, and it's all due to blockage in
the xylem in the water
conducting tissue. More recently the big disease in
late blight. the news here in the state was
And that really started in 2009. Now, late blight has been around
Any of you Irish ancestry in the forever.
room because of late blight. audience? I certainly am. We are probably sitting in this
That's what caused the Irish potato famine in the 1840s and
moving out of Ireland. '50s and led to lots of folks
Caused a lot of deaths through starvation as well. We've had late blight in the
state in the past.
It was just prior to 2009. We hadn't seen late blight for
And when it came in it was very, about seven years.
lots of variants of the verypathogen.ing. And some of the variants, like causes late blight but there are
but they will infect tomatoes. potatoes, a little bit better
potatoes and it took a long, The variant that came in 2009 preferred tomatoes. We saw our first cases in
long time for us to see the disease on potatoes. Interesting, the first case on
potatoes in 2009 was in one of
our Extension entomologist's test plots at Arlington.
And particularly because his He was very chagrinned.
[LAUGHTER] wife was a late blight expert through USDA as well. That didn't help as well.
The number two case on tomatoes, I have to acknowledge this as well, the number two case in
the state, actually on any crop,
was in my dad's home garden. I was accused by certain folks
tomatoes, but that was not the of inoculating my dad's
case. [LAUGHTER] It was really funny.
He called me, they were going to
a flea market or something and they wanted me to let their dogs
our tomatoes are wilting, could you please take a look at them. And I walked about four feet out, and they said by the way
late blight. away from them and I knew it was
This is a very destructive disease.
and the reason why it is so important is because we have a And it basically kills plants
huge potato industry here in the state.
And if the pathogen comes in and
anymore, it's a water mold, but spores can be produced that can eventually end up in our potato producing areas in Wisconsin.
So large impact.
We did a lot of testing for this, did a lot of testing for free.
In 2009, we did about a hundred samples for free. Virtually all of them were
We offered the same sort of service in 2010, and virtually positive for late blight.
none of them were late blight. Most of them or more common
disease of tomatoes called
from the bottom up. sVery, very common. It's one of the diseases that causes the tomatoes to defoliate
Other diseases that we've seen, I really know that I've arrived as a plant pathologist or that that for free.
science when I hear a segment on plant pathology has arrived as a
NPR about plant disease. And there was actually an NPR piece, I believe it was last
year, on basil downy mildew.
And I think the number two case was actually in my neighbor's reported cabackyard.consin last I went to film a segment on
vegetable diseases with Shelley Ryan again and I was looking for
enough it had downy mildew. It causes real yellowing in the otfoliage, and if you flip then I looked at their basil and sure
surface you're going to kind of grayish-purple, fuzzy material leaves over and look on the back
which is actually the pathogen sporulating on the undersurface
of the leaf.
And then more recently and every once in a while I'll get a call from a newspaper, particularly
in the eastern part of the
state. Although, there's a lot of this disease in Dane County
apparently this year. These leaves with these huge
and if you look very carefully black blobs, splotches on the leaves, very round oftentimes,
at the center of those round spots they look like somebody left a fingerprint in the
center. And this is a disease called
but we see if usually closer to the lake. And I think it was the Milwaukee Again, fairly cosmetic disease
and was asking for comments on Journal Sentinel that called me
economically, sometimes they're more cosmetic issues, but we do get some press every once in a Sometimes they're very important
And then my favorite diseases, while.
as Bob will attest, are the regulatory diseases. Ramorum blight is one that has a
long history. It's a disease that for a while was pretty much isolated to California, particularly
northern California and southern
Oregon. A lot of oak trees were dying in the area.
The original name of this disease was sudden oak death. And, unfortunately, one of the
out a whole bunch of plant nurseries out in that area sent
material from a site that they eventually discovered was contaminated with the pathogen.
And so there was a lot of work, when was that?
they had to follow all these About five years ago where tons and tons of, trace forward, so
plants had gone. plants from California to where they will been shipped and to try and track down where these
case in Wisconsin, but we still, And we still monitor for this particular disease. We've never found a confirmed
it's a disease that has regulatory impact. Huge potential impact on a wide
range of woody ornamental and also some herbaceous species as well. Plum pox is a disease, it's a
viral disease, that was found out east. We, again, we've never had a
but we continue to watch for it. confirmed case here in Wisconsin
It can be very, very problematic on Prunus species, so plums,
Again, we don't produce a lot of cherries, apricots, peaches.
those fruit crops here in Wisconsin, or at least not large amounts, so it's not as
important here as farther south.
Thousand cankers disease is another one we haven't seen here but it's kind of the current
disease of regulatory importance
that we're watching. It's been more of a problem in
it's called thousand cankers the southwest US on walnuts, and
because it's associated, actually the pathogen is fungal pathogen.
It's brought in by insects that tunnel under the bark, and every
where they tunnel an infection occurs, so you get lots and lots
of these insects visiting an
individual tree starting lots and lots of individual infections, thus thousands.
It really does look like there's
thousands of infections in the trunk.
brown areas on the wood. And you can see all of these
And it will kill walnuts. And we are very concerned about conglomeratithat.f individual There's kind of a quarantine or
you have to be very careful transporting wood out of areas
that have confirmed cases of the disease.
And so, again, the Department of
Ag is very concerned about that. I've been doing a fair amount of education in that particular
area. Probably the regulatory disease that I'm most proud of from my
Myself and one of my student standpoint is Ralstonia wilt.
hourlies as well as Caitilyn Allen who is our current
expert on this particular disease, and the group of us department chair, she's a world
were able to publish a first report of this particular
pathogen or a variant of the
pathogen on geraniums. There was a variant, we got these geraniums that came in
that were sick. They had this wilt disease. We got this, it's called
the plants, and I had an Ralstonia solanacearum out of
undergrad at the time who wanted to do a senior thesis and so I
variants, these little said, well, there are all these
specialized groups within this particular species of bacterium,
this is. go and find out which variant
potato production because it was We were expecting one variant and it came back as a different variant that had implication of
slightly more tolerant of cold weather.
which was very fortunate for And Lynn got a paper out of that
her. She did a great job on the
It was a nice feather in the project.
clinic's cap for having picked up on this. What's interesting about this is
that was pre-9/11.
After 9/11 the federal government developed the list of
particular bacterium, this select agents, and this
variant that goes to potatoes ended up on the select agent list.
And we had an introduction
post-9/11 where the FBI and Homeland Security got involved because we had to determine,
well, DATCP and APHIS had to
determine whether it was an accidental or an intentional introduction.
And as it typically the case
these are accidental introductions.
post-9/11 how this disease was But interesting pre-9/11 versus
with non-diseases. actually looked upon. And to kind of finish up, sometimes in the clinic we deal
In fact, this summer was really the summer of, in many ways, non-diseases.
Sometimes what we deal with are nutrient sort of deficiencies.
The most common one that we deal with is a problem in oaks called
chlorosis.
We have a lot of limestone bedrock here in Wisconsin, and
soil PH to be very, very high. it tends to really cause the
And when we have high soil PHs what that basically means is
so the trees can't take it up, iron gets locked up in the soil
And, again, it's not really a and you getdisease.ery yellow oak leaves with very distinct green veins.
There's no microorganism involved.
It's really a fertility or a
soil PH issue. Similarly, if you ever grow tomatoes you probably had
blossom end rot where the bottom
of the fruit rots away. Again, it looks like a disease but it's not.
There's no real microorganism that causes that disease. It's a nutrient deficiency. It's basically a lack of calcium
in the fruits.
The big non-disease that we dealt with this year is in the center.
There was a new herbicide put on
the market called Imprelis. Did a great job on controlling things like violets and other
broad leaf weeds in lawns.
testing, that under certain Uconditions it could be a great didn't realize, even though they'd done a fair amount of
herbicide for spruce and pine as well.
And so there are hundreds if not
thousands of trees that have been severely compromised or
herbicide. even killed through use of this
distorted growing points. The tips of the branches were very elongated, very twisted. The needles were very tan and
really disgusting looking from
uptake of this particular herbicide. And then sometimes we see what I
consider really cool organisms
cool. The one on the top is what we affectionately call dog vomit slime mold because it looks like
somebody's dog has up-chucked in
your mulch. These are very common when you have spread new mulch.
And they are very, very transient.
They usually only last about a week but they're very colorful
and they look very disgusting.
And if you really want a hoot, do an Internet search on Texas
Back in the mid-'70s they had a lot of this pop up, and they and slime molds.
[LAUGHTER] thought it was an alien invasion.
It does look kind of weird. And then we get the rather embarrassing fungi, the
stink horns that look like a
particular piece of anatomy. I get phone calls about those.
discussion. These are fungi. It's a very kind of embarrassing
very weird. I vacation down at Disney World Theroutinely and I was very,ike strvery excited two years agoy,
because I saw three different types of stink horns at the resort where I was vacationing. So I was in plant pathologist
heaven. So we do see a lot of different things that are really, really
Like I said, I love my job and I cool.
hope I've conveyed some of that tonight. I'm going to stick around for a
while if you have specific
questions that you'd like to ask.
after we're done here tonight, But if you think of anything
feel free to contact me. This is my contact information. You're welcome to give me a
call. Also, it's usually pretty easy
to get a hold of me via email. Just be patient, sometimes it's
really crazy in the clinic and
Also you can visit my website itand also the UW Extensionet horticulture website for a lot messages.
plant diseases and other cool stuff. of additional information on
Thanks, Tom. [APPLAUSE]