PA_APRMAY2017

22-23 / 36

22 | April/May - 2017 | 23
R&D | ASK THE INDUSTRY |
A Soil Moisture Assessment Treatment (SMART) test has been developed to assist
growers in knowing when to apply a crop protection product. Syngenta Technical
Services Lead Scott Mathew provides advice on how to best use the test and the
factors that may affect crop protection product application.
DEVELOP ING SMARTER CROP TESTING
With the unpredictable weather we have experienced this summer,
growing conditions have resulted in vigorous potato plants and
higher than usual weed counts present in crops. As a result, halting
plant growth and controlling weeds for harvest may prove a little
more difficult this season. Desiccating potato crops offers growers
management advantages by aiding the harvest process and
improving tuber maturation. As a result, a few common questions
come up at this time of the year, as outlined in this article.
I HAVE HEARD OTHER GROWERS TALK ABOUT THE
SMART TEST – WHAT IS IT AND HOW DO YOU DO IT?
Syngenta developed the Soil Moisture Assessment Treatment
(SMART) test as a practical and simple way to assess when the crop
is at the right stage to apply REGLONE®. There are four steps to
the test, but in short it involves “hands-on” soil moisture tests using
a spade in the field (be prepared to test at several sites).
Steps to complete the test:
1. Dig down and take a soil sample from the centre of the ridge
(five centimetres below the deepest tuber).
2.Gently squeeze the soil sample into a ball with your hands. If it
is sufficiently moist to pass the test, it will remain as a ball. If it
collapses, it has failed the test.
3. Repeat at several points across the paddock, especially in drier areas.
the soil test is a fail or borderline, delay product application
until the soil is moistened by rainfall or irrigation.
the test is a pass, choose the rate of the product dependent
on the haulm condition.
WHAT COULD CAUSE UNEVEN DESICCATION RESULTS
WHEN USING REGLONE®?
As with the use of any crop protection product, always read the
label directions before use. Getting a good result from use of this
product has some critical elements, but it comes back to attention
to detail with application, including environmental conditions and
the condition of the vine itself.
1. Choose the correct rate to match the amount of green material
you want to desiccate (i.e. the more vine present, the higher the
rate needed).
2.For the best results, an even and complete coverage and good
penetration of the spray into the target foliage is necessary.
3.Aim for a fine to medium spray quality with a minimum of 100
litres of water per hectare (L/ha). Use higher water volumes (200
to 300 L/ha) to obtain coverage of dense haulm.
DO ANGLED NOZZLES AID THE USE OF REGLONE®
FOR DESICCATION?
The theory and practice behind angled nozzles is to provide
greater coverage and spray penetration into a broad leaf canopy,
among other benefits. Angled nozzles such as the Syngenta Potato
Nozzle (which has a 30° angle nozzle tip) is an XR 110 04 nozzle.
Originally designed for fungicide use, it has proven to be very
effective for use with this product when desiccating vines. Use the
Potato Nozzle alternated forward and back along the boom for
best results, with a recommended water volume of 200 L/ha.
CAN SPRAY.SEED® (PARAQUAT + DIQUAT) OR STRAIGHT
PARAQUAT-BASED PRODUCTS BE USED TO DESICCATE
POTATO VINES PRIOR TO HARVEST?
No. Paraquat-based products are not registered in Australia for this
purpose. SPRAY.SEED® (paraquat + diquat) has a specific warning
to not use the product for potato haulm desiccation. The only crop
protection product registered for this purpose in Australia is diquat
200 g/L (REGLONE®).
For more information or to ask a question, please contact your local Syngenta
Territory Manager, the Syngenta Advice Line on 1800 067 108, visit syngenta.
or email Potatoes Australia: . Please note that your
questions may be published.
The R&D content for this article has been provided to Potatoes Australia to
educate Australian potato growers about the most relevant and practical
information on crop protection technologies and their on-farm applications.
This communication has been funded by Horticulture Innovation Australia Limited
using the research and development Fresh Potato Levy and funds from the
Australian Government.
Project Number: PT15007
INFO
Verticillium wilt is often difficult to detect in
potatoes, however it has been found to be
closely associated with Potato Early Dying
syndrome. Professor Paul Taylor from the
University of Melbourne provided Potatoes
Australia with a research update on the disease.
GAINING AN
UNDERSTANDING OF
VERT IC I LL IUM WI LT
Verticillium wilt is a damaging soil borne disease of potatoes, where
the pathogen infects, colonises and causes wilting in plants. It is
likely to be present in all Australian potato fields, with the potential
to cause crop losses ranging from one to 20 per cent.
Previous research shows that it is linked to Potato Early Dying
(PED) syndrome, which can be caused by an interaction between
different species of the soil borne fungal pathogen Verticillium
(Verticillium dahliae and the lesser common Verticillium albo-
atrum) and the root lesion nematode (Pratylenchus crenatus).
Often there is no distinctive visible symptoms of Verticillium wilt
other than general poor health of potato crops, such as yellowing
of foliage and wilting. Other host species of Verticillium wilt include
pigweed, nightshades, bindweed and thornapple.
Professor Paul Taylor from the University of Melbourne supervised
a project funded by Horticulture Australia Limited (now Horticulture
Innovation Australia), entitled the Australian Potato Research Program
Phase 2 (APRP2), which included a focus on Verticilliumwilt research.
“Our first objective was to understand the interaction of
Verticillium dahliae, which is the major Verticillium, with nematodes
to investigate if it had an interaction that was responsible for
producing Potato Early Dying symptoms. We did extensive surveying
of tubers that were coming from fields and found that Verticillium
was quite widespread,” Professor Taylor explained.
“We reproduced the disease in the glasshouse, using
inoculation techniques to develop a model that could be used
to identify resistance in varieties of potatoes grown in Australia
under controlled conditions, as well as to assess the efficacy of
some organic supplements to see if it was possible to suppress
some of the pathogen.
“Also we detected a few cases of tubers in Tasmania and
Victoria infected with Verticillium albo-atrum , which plays a
predominant role in disease in potatoes in the United States. It
doesn’t seem to play the same sort of role in Australia and we
don’t quite know why, so that’s an area of research for the future.”
DISEASE MANAGEMENT
Potato growers are advised to determine the level of inoculum
in their soil by obtaining a proper diagnosis of Verticillium using
the DNA-based soil testing service, PreDicta Pt, developed by the
South Australian Research and Development Institute (SARDI).
If the results confirm the Verticillium pathogen, Professor Taylor
said growers are recommended to remove potato plants and
tubers from the field at harvest.
“Also, they should clean the field up and then practice crop
rotation or use a non-host plant, which may be going into
pasture. I know this is often not the way with high intensive
production, but the only way to try to reduce the disease in the
soil is to avoid planting potatoes back into it.”
Another aspect of Professor Taylor’s work was to identify the
level of resistance of Verticillium wilt in current potato varieties,
which could also be used to manage the disease.
“An outcome of that was the identification of a particular variety
called Denali, which had reasonable levels of resistance that
hadn’t been found before,” he said.
A screening of several Australian potato cultivars for resistance
to Verticillium dahliae in glasshouse trials showed that some
varieties are considerably more resistant than others. This work
could be repeated in commercial fields to study resistance of
commercial potato cultivars.
CURRENT RESEARCH
According to Professor Taylor, more research on Verticillium wilt
needs to be undertaken.
“We’ve understood that there is a problem and we now have
a model system that we can use to study the disease in more
detail,” he said.
“At the moment, we have another PhD student (Mee-Yung Shin)
looking at the mechanism of resistance. We’re looking at taking
these resistance lines and understanding the resistance that’s in
line to prevent the disease from developing.
“It also needs field trials to assess the varietal resistance in the
plants. Some of the future work is using molecular techniques to
look at the inoculum levels in particular fields, to see if it’s evenly
distributed and just how the fungus exists in nature.”
For more information, please contact Professor Paul Taylor at paulwjt@unimelb.
or turn to page 26 to read about PhD student Mee-Yung Shin’s research
on Verticillium wilt.
The topic for this article was selected following the results of PT13013 A review
of knowledge gaps and compilation of R&D outputs from the Australian Potato
Research Program.
This communication was funded by Horticulture Innovation Australia Limited
using the research and development Fresh Potato Levy and funds from the
Australian Government.
Project Number: PT15007
INFO
L-R: Professor Paul Taylor and Mee-Yung Shin.
Image courtesy of the University of Melbourne.
R&D | RESEARCH UPDATE |