GCTV Ep#9 Supplement – Botrytis in Chickpeas
Darryl Anderson: Presenter Hello I’m Darryl Anderson.
In this first GroundCover TV supplement for 2013 we’re going to look at emerging Pests,
Diseases and Weeds.
We’re not talking about things previously undiscovered but rather the emergence of concerning
developments such as the spread of herbicide resistant weeds and Redlegged earth mites
developing resistance to insecticides.
But to start we’re going to look at the emergence of fungicide resistance and begin
with an update of a story we reported last year, fungicide resistance in barley powdery
mildew…
Tony Crowley: Reporter This is a model of C-y-p-51, a protein found
in the pathogen that causes the fungal disease barley powdery mildew.
What makes this particular fungal protein very significant is that if a strain of barley
powdery mildew is to become resistant to a fungicide it most likely will be because of
a mutation in this gene.
Richard Oliver: Professor of Agriculture Curtin University WA
Fungicides that used to be successful at controlling barley powdery mildew particularly Tebuconazole
and Triadimenol are now failing to control.
Reporter: Professor Oliver’s team has been taking
isolates from field samples of the fungus and exposing them to the various fungicides
at different concentrations.
Resistant isolates then have their DNA sequenced and crosschecked against mutations known to
have resistance to the DMI also known as the Triazole group of fungicides.
Darryl Anderson: Narrator Since that story was produced in September
2012 Richard Oliver’s Western Australia based team has been able to expand on its
work.
Isolates of the powdery mildew pathogen from eastern Australia have been compared to the
mutant mildew found in the West and that’s where Richard picks up the story.
Richard Oliver: What we found was the isolates of the pathogen
from WA have a different mutation from the ones from South Australia and Victoria, Tasmania
and New South Wales.
Those isolates from eastern Australia do not have this new mutation which means they’re
still susceptible, still well controlled by products with Tebuconazole in them for example.
But we would also say that the WA experience has shown that that’s a risky situation.
Narrator: Risky, according to Professor Oliver, because
the continued exposure to this particular group of fungicides will eventually lead to
the building of resistance in eastern Australia.
Rotating the Tebuconazole group with other fungicides, using mixtures and applying the
lowest recommended rates will instead prolong their usefulness.
The research goes on.
Jenny Davidson: Senior Pulse Pathologist SARDI So this is where Botrytis has affected the
chickpea pod.
Narrator: Jenny Davidson is another scientist studying
fungal pathogens.
Jenny Davidson: There are millions and millions of spores
out there in crops.
We’re collecting hundreds so we’re only collecting a very small sample of what’s
out there and of those hundreds over 10 years we’ve found one that is resistant.
So it is a very small number at this stage that is resistant but if the pressure is put
on that population and lots and lots of fungicide is put out it will mean that that resistant
type will have an opportunity to multiply up.
Narrator: That one isolate of Botrytis cinerea, which
was resistant to Carbendazim, and found in a South Australian chickpea crop, was enough
to flag a warning about the emergence of fungicide resistance.
And to avoid that possibility pulse growers have been advised to strictly follow chemical
label application rates.
Jenny Davidson: The first thing growers should be doing is
reading the label recommendations and understanding the regulations as to how many sprays of a
particular ingredient they can put out on a crop.
And with things like Carbendazim and Procymidone it is only two sprays that they can put in
a particular crop.
So if they stick to that then they will be able to control or reduce the level of fungicide
resistance building up in their crops.
Narrator: Jenny Davidson is also researching the timing
of spray applications and says growers of any pulse crop need to be very strategic about
when they are put out fungicide sprays.
Jenny Davidson: The first spray that goes out is before you
even see the disease.
We time that with crop growth stage.
We know when the canopy closes over is the last opportunity to get fungicides down to
the base of the plants.
So we say to our growers for faba beans and lentils in particular, always put out a fungicide
spray at that point.
So we have gone to a lot of effort to work out what is the best time to put out the sprays
to get the maximum return and the maximum control of the disease.
So that whole epidemiology and understanding how the disease works, how it performs under
different weather conditions has been very crucial to getting those fungicide strategies
understood.
Narrator: Botrytis is a fungus that can survive long-term
in the soil or on plant litter as sclerotes, non-fruiting structures.
Under warm wet conditions the fungus activates and spores can spread rapidly, making crop
monitoring an essential management strategy according to Jenny Davidson.
Jenny Davidson: It will infect the flowers and they will rot
and fall off so of course that means no pods and no grain for the farmer to harvest.
In faba beans and lentils it also attacks the stems so that the whole plant will fall
over and then the whole plant dies so obviously then you get no grain from those plants that
die off.
And it will move very rapidly across a paddock, you will see big patches dying out very very
quickly.
So you can understand from a grower’s perspective why they want to get those fungicides out
and why they are really keen to get this disease under control.
But in terms of getting their fungicides out they have to get them out early before the
disease is spread.
Because once its started spreading they come in behind with a fungicide and they’re not
going to get the control they want so they put out another fungicide and it may well
be they keep putting out fungicides that means then that you are putting the pathogen under
pressure and that’s when you start running into potential fungicide resistance problems.
Narrator: In the lab its divide and multiple to build
pathogen numbers, in the field nature can do the job even faster and on a large scale.
Jenny Davidson: A lot of the diseases we work with are wind
borne, they’re spread around by the wind, the spores are produced by the fungi and then
blown very long distance.
So we’re setting up some research where we have spore traps that suck the wind in
and then they capture the spores on sticky tape.
Then we assess the spores using a DNA lab here.
It can quantify how many spores of different fungi are sitting on those tapes.
So we set them up in different places around the state.
We‘re looking at the impact of different weather conditions, whether it’s rainfall,
temperature, humidity, wind and all these sorts of things and the impact that has on
spore dispersal and just where these different fungal spores are spreading around.
Narrator: Understanding the climate’s impact as well
as a pathogen’s development makes it possible to give growers even more strategies to reduce
the risk of fungicide resistance emerging.
Jenny Davidson: Because we know so much about the epidemiology
of Black Spot we know when those airborne spores are being released from last year’s
stubble and so we monitor that and in many years those spores are released before the
crops come out of the ground.
So the farmers can change their sowing date according to the timing of that spore release.
Effectively then they can eliminate the risk of Black spot in their field peas.
Narrator: Black Spot is Ascochyta blight and North America’s
experience with this particular fungal pathogen provides another example of what not to do.
Jenny Davidson: They’ve been using the Strobilurins quite
a lot and our understanding is that they have put out many many Strobilurins applications
in chickpeas and as a result they’re finding that those Strobilurins will not control the
Ascochyta in chickpeas.
So that’s another warning sign for our industry because we’re starting to move towards registration
of these particular fungicides in our pulse crops and we need to be aware that we have
to use them properly so that they can remain affective over a long period of time.
Narrator: So how important is it to protect the efficacy
of the fungicides that are in use?
Jenny Davidson: It’s very important because we just aren’t
sure how many of these actives are going to be available to the industry in the future.
There are a whole suite of different fungicides in the world but these are being more and
more restricted in their use particularly in the European Union and quite often we do
follow the world regulations in that area so we may find that less and less fungicides
become available to the industry so we need to protect what we’ve got.
Narrator: When specialist farm consultant Jim Orson
was in Australia last year to speak at GRDC advisor updates he highlighted the concern
in the UK over the European Union’s regulations on farm chemical use.
Jim Orson: The Arable Group United Kingdom So we don’t know yet the real impact of
some of this regulation in terms of pesticide availability but estimates have been done
and it could mean that we’ll lose a lot of useful pesticides to broadacre cropping.
There’s a list of 22 or 26 depending on what standard you look at some of which can
have important herbicides of grass weeds control, Pendimethaline, and also more critically very
valuable fungicides.
We use a lot of fungicides in Europe, we have a lot of fungal attack in cereals, they create
huge yield increases, or prevent huge yield losses, and some of those are actually on
this list, which could be at risk.
So we do really worry about that.
Narrator: Back here in Australia the outlook is positive.
To support growers in managing future fungicide resistance risks, GRDC has invested in the
Australian Centre for Necrotrophic Fungal Pathogens at WA’s Curtin University and
supports projects undertaken by independent research company Kaylx Australia and applied
research organisation FAR Australia, The Foundation for Arable Research.
Via these research providers GRDC is also working in partnership with chemical manufacturers
to deliver new fungicides with modes of action suitable for use in cereals and pulses, while
also protecting the usefulness of current fungicides.
ENDS
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