Australia
November 11, 2008
Source:
GRDC's The Crop Doctor
 Before
or during harvest is not too late to check crops for Cereal Cyst
Nematode (CCN) and decide on rotations and management plans for
next season.
CCN can cause severe damage under
continuous cereal cropping and in WA is frequently reported from
the northern agricultural region around Geraldton and the
central agricultural region.
Have you noticed distinctive yellow patches in the crop that may
have been there in previous years and seem to be getting bigger
from year to year?
What about patchy areas of uneven growth and stunted, unthrifty
and yellowed plants with poor tillering?
Dr Vivien Vanstone (photo), Grains Research and Development
Corporation (GRDC) supported Senior Nematologist at the
Department of Agriculture and Food WA, advises growers to
carefully dig out suspect plants and wash soil from their roots.
Alternatively, suspect patches can be mapped or pegged for later
investigation and testing.
If barley or wheat roots appear shortened and knotty, or oat
roots are swollen and ropey, the cause is most likely CCN.
 |
|
Dr
Vivien Vanstone’s GRDC supported project showed plants
affected by CCN (right) are yellowed and stunted, have
fewer tillers and shallow, distorted root systems,
compared to unaffected plants (left). |
According to Dr Vanstone, female
nematodes invade roots in autumn and as they feed and develop,
their bodies swell and erupt through the root surface.
In spring, they can be seen as white spherical bodies, about the
size of a pinhead, on the root surface.
At this stage, female nematodes each contain hundreds of
developing eggs.
As the crop matures and the soil
dries, females turn brown and form a hardened cyst containing
several hundred eggs which hatch at the beginning of the next
season and infect the new crop in autumn.
Moist, cool conditions foster hatching, but only 70 to 80 per
cent of these eggs hatch each season, so some remain in the soil
for following seasons.
For this reason, it can take several years for high CCN
populations to be reduced below yield limiting levels.
Dr Vanstone advises that rotations incorporating legumes, canola
or grass-free pasture are effective against CCN. Where CCN has
been identified, no more than two consecutive susceptible cereal
crops should follow a non-host break crop.
Severe soil infestations will require more than one break crop
to significantly reduce levels. Controlling weeds, particularly
wild oat and volunteer cereals in non-host phases of rotations,
is also required.
Dr Vanstone says chemical treatments to control this nematode
are not available and cultivation is ineffective as it spreads
the cysts around the paddock, distributing them throughout the
soil.
Trials show non-host crops are more effective than resistant
cereals in reducing CCN levels.
A GRDC supported trial showed that when resistant cereals and
non-host crops were used as a management tool, CCN eggs in the
soil reduced by 84 per cent and 96 per cent respectively,
compared with susceptible cereals.
The Crop Doctor is GRDC Managing Director, Peter Reading |
|
 |
|
The Crop Doctor is
GRDC Managing Director,
Peter Reading |
|
