NatioNal variety trials supplemeNt - Grains Research ...

Weed kill without crop damage
Before spraying, growers and agronomists are encouraged to check NVT Online for
information on the safety of herbicide use on their varieties
Weeds and disease
12
By Emma Leonard
Crop yield can be compromised
by damage from herbicides, even when
products are applied appropriately at
the label rate. Varieties are known to
differ in their tolerance to herbicides
and this can vary between regions.
The good news is that more than 70
per cent of all crop varieties are tolerant to
most herbicides. The remaining varieties
can experience yield losses of 10 to 30 per
cent and, in some cases, 50 per cent yield
loss has been recorded. This occurs with
the use of registered herbicides applied at
label rates under good spraying conditions
at the appropriate crop growth stage.
To provide growers with clear
information about the herbicide interactions
of a variety for their region, four regionally
based herbicide-tolerance screening projects
have been established. The projects are
run by Jenny Garlange and Harmohinder
Dhammu, Department of Agriculture and
Food, Western Australia, Rob Wheeler and
Michael Zerner, South Australian Research
and Development Institute, Peter Lockley,
New South Wales Department of Primary
Industries, Steve Walker, the University
of Queensland and John Churchett,
Queensland Department of Agriculture,
Fisheries and Forestry (DAFF).
The four projects have recently been
combined under a national program,
coordinated by Mr Wheeler.
Results from all the herbicide tolerance
trials can be easily accessed via NVT
Online (www.nvtonline.com.au).
National approach
Screening of varieties for herbicide
tolerance has been undertaken in most
states since the early 1990s. The main crop
varieties tested were in wheat and barley.
The new coordinated approach
tests the tolerance to commonly used
in-crop herbicides of wheat, barley,
oats, peas, lentils, faba beans, chickpeas
and lupin varieties emerging from the
NVT. This will ensure that the tolerance
to important herbicides is known at
the time of a new variety’s release.
Crop types tested vary between regions
in relation to their importance in a region.
For example, lupins are only tested in WA.
Varieties and advanced lines are generally
tested for two or more years to validate
varietal responses and to minimise the
seasonal influences on herbicide tolerance.
The project also tests new chemistries
in collaboration with chemical companies.
“Independently testing a variety’s
herbicide tolerance before its market release,
ensures growers have the most relevant
information available to them when selecting
new varieties,” Mr Wheeler explains.
Herbicides are applied individually
and in tank mixes at label and above label
rates in weed-free field sites. Treated plots
are monitored for crop damage (colour
change, necrosis, biomass and stunting)
and compared to unsprayed plots.
Crop damage and retardation is assessed
visually and with crop sensors that measure
crop greenness using the normalised
difference vegetation index (NDVI).
These measurements help to establish if
observed damage results in yield loss.
Bringing these projects together in a
coordinated national program has enabled
research approaches to be standardised.
It has also facilitated collaboration on
projects such as those assessing genotype,
environment and herbicide interactions.
A significant step in the research has
been the development of a simple rating
system using symbols to categorise the
sensitivity of varieties, based on the
yield responses across all trials. Tables of
herbicide tolerance ratings can be found
at NVT Online (www.nvtonline.com.au).
A variety that has no significant yield
reduction from both the label recommended
rates and higher rates is marked with ‘’.
An ‘N’, indicating a narrow safety
margin, denotes significant yield reductions
at the higher-than-label-recommended
rate, but not at the recommended rate,
and these varieties are shaded in yellow.
When there is a significant yield
reduction at the recommended rate,
a warning is noted if recorded in one
trial only (shaded in brown) or in
two or more trials (shaded in red). In
these instances the magnitude of yield
reductions are noted in the table.
photo: Steve Walker
Researchers involved in the herbicide tolerance
screening work at an annual review meeting
in Birchip, Victoria. (From left) Hanwen Wu,
Kaylene Nuscke, Peter Lockley, Rob Wheeler,
Harmohinder Dhammu, Courtney Ramsey and
Steve Walker.
Regional application
Variety herbicide-tolerance testing for
wheat and barley has been carried out in
Queensland since 1999. More recently
chickpeas have been added to the project,
which is run by John Churchett, principal
experimentalist, Queensland DAFF.
In 2011, 22 trials were sown, treated
and harvested in the northern herbicide
tolerance project. This figure hides the
size of the project, which included the
testing of 32 NVT wheat lines with 12
herbicides (those considered to be the
most commonly used) in three trials and
the testing of 20 NVT barley lines with
eight common herbicides in two trials.
A further seven trials assessed advanced
wheat lines and new varieties that had
shown potential sensitivity to specific
herbicides in the previous season. In a
further two trials, the sensitivity of three
varieties and two lines of chickpeas
were tested with four herbicides.
Trials are located at sites across
southern Queensland to ensure
regional environmental influences
on herbicide–variety interactions are
also identified in this project.
The importance of conducting trials
across Australia has been emphasised
by the identification of different levels
of crop sensitivity to some herbicides
in the Northern Region trials compared
with results in the south and west.
This indicates a strong environmental
influence on herbicide tolerance. □
GRDC Research Codes DAS00100,
DAN00142, UQ00059, DAW00191
More information: Rob Wheeler, SARDI,
0401 148 935, rob.wheeler@sa.gov.au