Root lesion nematodes have become a hidden hindrance to northern grain growers, slashing
crop productivity and forcing a rethink of traditional cropping rotations.
Each year across the northern cropping belt, intolerant wheat and chickpea varieties are
impacted by nematodes with estimated yield losses of up to 50% and 20% respectively.
It’s probably hard to quantify, but if you had a crop doing say 3 tonnes a hectare, where
you had nematodes, you could be down to a tonne a hectare. Especially when they take
out the whole paddock when they spread.
Sometimes it’s only patchy but they are there, and the other interesting finding now
is the tie-in with crown-rot and how much damage the two combined together can cause
us.
Crown is just endemic on the plain; we just don’t seem to be able to get rid of it.
The nematodes we’ve got across half the farm from the late war to 70s, before we took
it over… all they did was grow wheat so it’s riddled with nematodes…so wheat is
really just a one in 10 year crop for us.
Rob Taylor is hosting a research trial that’s being conducted by the GRDC-funded Northern
Grower Alliance (NGA) on his 2000 hectare mixed winter and summer cropping property,
Curraweena in the central Darling Downs.
The trial has been run by NGA chief executive Richard Daniel and is evaluating three main
areas - the impact from increased nematode populations on variety yield, the impact from
varieties and crops on nematode build-up and the impact from management practices on yield
losses and nematode build-up.
With crown rot analysis also being undertaken as part of the trial, Mr Taylor is interested
in seeing the results of the interaction between crown rot and nematodes.
The other thing I’m hoping that comes out of the NGA trial is time of planting especially
for wheat, if we can go early does the plant compensate for those two pests…because the
way it’s looking if we have a late plant in winter, wheat is just out of the question.
Again, if we go back and say ok we’ve grown a variety of barley, what are the nematode
counts afterwards, whether it was lower or we’ve raised them, same with chickpeas,
and again on the wheat varieties – and also what varieties do hold high nematode numbers…that
will give us thought to what we can plant, not just going out and saying ok that looks
like a good variety, let’s go and whack it in…but for me having the trial on my
own farm does give me pretty good insight into what does perform here.
In the northern cropping regions, nematode numbers at two per gram of soil anywhere in
the profile is considered a damaging population. The NGA’s trial activity at Curraweena started
in 2013 in a paddock with an existing natural population of six per gram of soil.
If we go back three winters into where the trial is. We had planted 18m strips one of
Strzelecki wheat, the other one Caparoi durum, the Strzelecki lifted the nematode numbers,
whereas the Caparoi held them about where they are…if going on the soil test, even
where the Caparoi was there is still high nematodes… but this will give us very high
to high of what different varieties will come out if it.
Mr Taylor, who is a former GRDC northern region panel member, has seen a dramatic rise in
industry awareness about RLNs and their potential impact on crop productivity.
I’ll go back to when I started on panel and there was a lot of people growing old
wheat varieties and we couldn’t work out why haven’t they moved onto these newer
varieties, which were coming through in NVT saying they should be better... but I think
that’s really when people started to realise the nematode problem and how wide spread it
was, and started testing and saying ok we’ve got nematodes what can we do about it.
The NGA type model is set up so it can get money into the growers pockets in 1-3 years...the
information that comes out of this trial, even after one time will give information
to growers on how they can improve their practices or improve their choice of variety straight
away.
It’s a huge issue, yes, GRDC, especially through the northern panel has invested heavily
in nematodes and crown rot, so big trial work, but not just looking at the variety, but there
is breeding hopefully coming on.
Mr Taylor stressed that regular monitoring of population levels using the DNA-based soil
testing service PreDicta B® was critical to maximising crop yield and farming system
profitability.
I think people have definitely got to go and test and find out, especially if they see
a paddock that performs poorly or patches aren’t up to speed. Get a Predicta B, but
don’t just test nematodes, do a crown rot test before planting, and have a good think
about what the results are.