| Project
Title |
Lucerne
yellows disease: testing and extension of disease management strategies |
| RIRDC
Project No.: |
US-131A |
| Researcher: |
A/Prof.
Geoff Gurr |
| Organisation: |
The
University of Sydney (in transition to Charles Sturt University ownership)
Pest Biology & Management
Group
Faculty of Rural Management
PO Box 883
ORANGE, NSW, 2800 |
| Phone: |
(02)
6365 7551 |
| Fax: |
(02)
6365 7590 |
| Email: |
ggurr@csu.edu.au |
| Objectives |
·11 The aim of this
project is to build on earlier RIRDC-funded work in which the pathogen
and vectors responsible for Australian lucerne yellows disease were determined
and in which tentative disease management strategies were identified. This
project will produce a 'toolkit' of disease management approaches that
growers will be able to draw from to better manage this important plant
disease. These strategies will include measures to reduce immigration into
lucerne crops of disease-carrying leafhopper insects and remove the non-crop
hosts of the pathogen as well as management to alleviate the severity of
symptoms in infected plants. Reflecting the regional differences in lucerne
production and integrated pest management (IPM) practices, research will
take place in both NSW and South Australia. The optimal disease management
strategies will be extended to growers by an illustrated, colour 'ute guide'-type
tool with more detailed information available on a farmer-friendly web
site. The rigour of the outcomes will be assured by submitting findings
to a peer-reviewed journal (Australian Journal of Experimental Agriculture).
|
| Background |
This
project built on earlier RIRDC-funded work that established the impact
of ALuY disease and generated information on possible disease management
approaches. |
| Research |
Polymerase
chain reaction (PCR) assays were used to test for the DNA of phytoplasmas
in lucerne plants collected from stands in NSW and SA. Insects suspected
to be the vectors of the phytoplasmas were also tested using PCR. Field
surveys in NSW and SA identified plants that harboured potential vector
species and these plants were also tested for presence of the phytoplasmas
using PCR. Seeds, and the seedlings grown from them, were likewise assayed
for phytoplasma using PCR. Field experiments evaluated the efficacy of
pesticidal treatment of field margin vegetation and of barriers on the
perimeter of lucerne crops for preventing immigration of leafhoppers. |
| Outcomes |
This
study has identified several plant species other than lucerne that harbour
a phytoplasma that is associated with ALuY. These plants could constitute
a significant reservoir for the pathogen and lucerne growers could now
trial the use of control methods (such as tillage, grazing or herbicide)
to suppress these species when in close proximity to newly sown lucerne
stands. The rationale for this is strengthened by the finding of large
numbers of the leafhopper on these plants and the fact that some of the
field collected individuals tested positive for phytoplasma. Insecticidal
control of this leafhopper could be warranted when it is present in large
numbers within or adjacent to newly sown lucerne seed crops. The most exciting
finding from the present work is strong evidence for seed transmission
of one of the phytoplasmas found to be associated with ALuY. Thought this
is contrary to generally held views on how phytoplasmas are transmitted,
it suggests that inspection of seed crops, more careful seed certification
requirements (possibly involving diagnostic tests for phytoplasmas) and
only judicious use of ‘home saved’ seed may play an important role in future
ALuY disease management. |
| Implications |
Pesticidal
treatment of non-crop vegetation around lucerne crops and barriers mounted
on existing fences appear to be ineffective in preventing vector insects
migrating into lucerne stands. Control of Australian lucerne yellows disease
will need to focus on the weeds that can harbour the pathogen and the insect
that vectors it into the crop. When found in close proximity to lucerne,
consideration should be given to the removal of these weeds. Insecticide
application should be considered if large numbers of the leafhopper Orosius
orientalis are found in lucerne, especially newly sown stands. The
phytoplasmas associated with Australian lucerne yellows disease may well
be seed borne, necessitating more careful phytosanitary arrangements. |
| Publications |
Getachew,
M.A., Mitchell, A., Gurr, G.M., Fletcher, M.J., Pilkington, L.J., and Nikandrow,
A. 2007. Plant Disease 91: 111.
Gurr G.M., Getachew M.A.,
Fletcher M.J., Mitchell A., Nikandrow A. and Pilkington L.J. (2007). Australian
Lucerne Yellows Disease: Testing and extension of disease management strategies.
RIRDC Publication No. 07/120. |
