GCTV Ep#6 Diamondback Moth
Narrator: Julian Doudle’s a farmer from the Lower
Eyre Peninsula, growing wheat and canola against the
backdrop of the Great Australian Bight.
In 2007 diamond back moth demolished the canola crop at his farm over on the coast; a
complete write-off.
Julian Doudle: “Newlyn Glen” Mt Hope SA “They attacked so quickly and so hard that
it was very difficult to have any measures in place to
combat them and I think that we just didn't know that they could do so much damage in
so short a time.
It was just a 0.8 crop going to just simply stick in a very quick amount of time.”
Narrator: Pretty impressive for a pest that hadn’t
really been on their radar.
And to complicate matters the moth was already resistant to synthetic pyrethroid just from
being around when previous crops were sprayed for
heliothis.
Nigel Myers: Agronomist, Cummins Ag Services “We had levels of up to 85-95% resistance
to lethal doses of synthetic pyrethroid.
From there we knew we had to start looking for different
active ingredients for control of diamondback moth
larvae.”
Narrator: An approach to GRDC via the Lower Eyre Agricultural
Development Association, and the search began.
Finding candidates wasn’t a problem – diamondback moth is a pest of other Brassica
crops too, and in the horticulture sector there’s bunch of products registered to
do the job.
One of them - Emamectin - emerged as the one with the best prospects of gaining registration
in the shortest time.
GRDC got SARDI Entomologist Greg Baker onto the job of generating the necessary data for
a registration.
Greg Baker: Senior Entomologist, SARDI “Field trials to demonstrate the efficacy
of Emamectin benzoate as a DBM insecticide.
So those data sets can be provided to the APVMA and
in turn the residue studies that need to accompany that registration claim.”
Narrator: Going to take a while to get enough data for
a full registration, but in the face of a big moth
outbreak mid season in 2011, the data so far was enough for GRDC to seek special
consideration.
In August 2011 the APVMA signed off on an emergency permit.
Within days, aerial operators in the Lower Eyre Peninsula
were getting very busy.
The local farmers were stoked.
Mark Modra: Spokesperson, Lower Eyre Agricultural Development Association
“It was hugely important because we had this outbreak in July and some of the agronomists
who partner with LEADA they pointed out that we
had some high levels of DBM in July and if you've
got high levels in July, by the time you get to September you've got a huge population
which could decimate the industry.”
Narrator: With the emergency permit in place, the local
resellers were being extra careful to make sure that
producers understood how they were permitted to use the product – and particularly the
withholding period that applied.
Nigel Myers: “It's 28 days to windrowing, so once a grower
has applied that product to the crop they cannot cut
that down for 28 days, so that's one of the things we've stressed”
Narrator: As it turned out, spraying didn’t carry
on for long - cooler weather and a bit of rain did the job of
reducing larvae numbers for free, taking the crop right up to the 28 day exclusion period.
While everyone had been very happy to have the option
to spray, no one was complaining about not needing to.
Darryl Anderson: Reporter “No-one's kidding themselves that with one
new chemical registration we've got this DBM problem licked.
This is after all a moth that has already shown itself to be very adept at
developing resistance to new chemicals.”
Greg Baker: “DBM has international notoriety as one
of a handful of insects with phenomenal capacity to
develop insecticide resistance and has developed resistance to every insecticide that has been
registered for its control over the past 50 years and has continued to do so.”
Narrator: The moth’s lifecycle makes it especially
tricky to target with a single insecticide.
Greg Baker: “Unlike heliothis, army worms, where at
the time you're targeting that pest the entire population
are present as caterpillars, with DBM you're faced with all stages from egg to adult present
in the crop at the time you need to be spraying.
And it's only the larvae which are controlled by the
insecticide treatment so it's a far more challenging pest to get good insecticide control.”
Narrator: While Greg Baker and his team keep working
to provide data for new insecticide registrations, he
believes this pest will demand a much cleverer approach.
Greg Baker: “We can't rely purely on the continual cascade
of new chemistry to deal with this pest.
It will rely on a much more sophisticated understanding
of the ecology and the resistance mechanisms at
play.”
Narrator: Having sounded the alarm bells in the first
place, the producers of the Eyre Peninsula and their
agronomists will be hanging on every new development from the research.
Julian Doudle: “I don't know the correct figures for the
amount of canola grown in the Lower Eyre Peninsula, but
it's a significant cash crop for us especially inland and ongoing work is going to be needed
to help alleviate the problem”.
END
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