Controlling weed recruitment in isolated areas of Cape York ......Sicklepod (Senna obtusifolia)...
Transcript of Controlling weed recruitment in isolated areas of Cape York ......Sicklepod (Senna obtusifolia)...
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Controlling weed recruitment in isolated areas
of Cape York Peninsula
Melissa Setter Biosecurity Queensland
Stephen Setter Biosecurity Queensland
Darryn Higgins Cook Shire Council
Simon Brooks Biosecurity Queensland
Wayne Vogler Biosecurity Queensland
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• Sicklepod
• Bellyache Bush
• Gamba Grass
• Grader Grass
• Giant Rats Tail Grass
Cape York Peninsula’s worst weeds include:
• Rubber vine
• Pond Apple
• Lantana
Sicklepod is the example species used in this study.
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Sicklepod (Senna obtusifolia) description
• Competitively vigorous woody shrub
• 1.5-2.5m tall x 1m wide
• 3 opposite pairs of leaves
• Small yellow flowers
• Sickle shaped pods
• Pods 10-15cm long, 3-5mm wide
• 24-28 seeds per pod
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Sicklepod lifecycle
• Short lifecycle
• Usually annual, can perreniate
• Seeds produced during dry season
• Dispersal by dehiscence, water,
mud adhering to vehicles, stock,
people etc
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Sicklepod flowering at very small size (May)
Sicklepod can produce seeds
within 6-10 months of
emergence
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Sicklepod in flower (May)
After seedfall (Aug)
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Up to
8000 seeds
per
plant
annually
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How
long
does
seed
last?
At least 2 years
Some say 10+ years
Checking in Qld: wet & dry
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Sicklepod distribution from https://avh.ala.org.au
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• Local gov’s
• Beef industry
• Sugar industry
• Parks and Forestry
• Indigenous land use
• Environmental
Sicklepod impacts- loss of production, management costs and environmental impact
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Cape York Peninsula
averages approximately
1305 mm annually
Wet season
inaccessibility
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Wet season inaccessibility
Controlling “remote”
infestations becomes
impossible
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Sicklepod
in May
While infestations are inaccessible, the plant continues to flourish
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• Slashing to control flowering can cause some mortality
• Foliar herbicides are quite effective
• Both methods can work, but only on accessible plants
• Current post-emergent herbicide control is effective,
but inaccessible plants are able to reproduce
• Biocontrol has been investigated, but not currently used
Sicklepod current control methods
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Sicklepod Herbicide control
recommendations from DAF factsheet
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To try to help break the life-cycle,
we investigated the use of herbicides that
could be applied when plants are accessible,
to kill emerging seedlings when access is
impossible, i.e. pre-emergent herbicides.
Pre-emergent herbicides
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We conducted a pot trial to test
16 herbicides
at 3 rates each
for their potential
pre-emergent effects on Sicklepod seeds
Pot trial methods
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Herbicides and rates were chosen on their known and potential pre-emergent effect.
We made sure to include the herbicides and rates registered and commonly used already on sicklepod.
Herbicides tested
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Herbicides and application rates used in the trial.Group Trade name Active Ingredient Low Med High
B Mako sulfometuron methyl 750g/Kg 0.4 kg/Ha 0.6 kg/Ha 0.8 kg/Ha
B Arsenal imazapyr 250g/L as isopropylamine salt 1 L/Ha 1.5 L/Ha 2 L/Ha
C Bobcat hexazinone 250g/L 3 L/Ha 9 L/Ha 15 L/Ha
C Metribuzin 750 WG metribuzin 750g/Kg 0.5 kg/Ha 1.25 kg/Ha 2 kg/Ha
C Graslan tebuthiuron 200g/Kg 5 kg/Ha 7.5 kg/Ha 10 kg/Ha
D Treflan trifluralin 480 g/L 1 L/Ha 2 L/Ha 3 L/Ha
G Valor WG flumioxazin 500g/kg 0.4 kg/Ha 0.7 kg/Ha 1 kg/Ha
I Stuka flexi picloram 240 g/L as potassium salt 0.93 L/Ha 1.25 L/Ha 1.57 L/Ha
I Grazon extra triclopyr 300g/L + picloram 100g/L as hexyloxypropylamine salt+ aminopyralid 8 g/L 2.25 L/Ha 3 L/Ha 3.75 L/Ha
I Conqueror triclopyr 300g/L + picloram 100g/L as hexyloxyproplamine salt 2.25 L/Ha 3 L/Ha 3.75 L/Ha
I Tordon 75-D 2,4-D 300g/L + picloram 75 g/L as triisopropanolamine salt 3 L/Ha 4 L/Ha 5 L/Ha
B Brushoff metsulfuron -methyl 600 g/kg 0.03 kg/Ha 0.075 kg/Ha 0.12 kg/Ha
H Balance isoxaflutole 750 g/Kg 0.1 kg/Ha 0.2 kg/Ha 0.3 kg/Ha
I+B Stinger aminopyralid 375 g/kg + metsulfuron-methyl 300 g/kg 0.06 kg/Ha 0.15 kg/Ha 0.24 kg/Ha
G Goal Tender oxyfluorfen 480 g/L 1 L/Ha 2 L/Ha 3 L/Ha
I Tordan regrowth master triclopyr 200g/L + picloram 100g/L as triisopropanolamine salt+ aminopyralid 25 g/L 2.25 L/Ha 3 L/Ha 3.75 L/Ha
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The average number of live sicklepod seedlings in each treatment approximately four months after treatment. The Least significant difference between treatments is 4.569 at P<0.05)
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• There were significant treatment effects at four months after treatment
• Herbicides containing Picloram caused high levels of control, including Conqueror®, Grazon Extra®, Stuka flexi®, Tordon 75-D® and Tordon Regrowth Master®.
• The herbicide Pledge® was also effective at the “high” application rate.
Some good results:
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Sicklepod example pots at 3 MAT
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We were able to identify several effective herbicides in
a pot situation, and rule out many others.
We now plan to apply the successful herbicides in field
conditions.
Sicklepod (Senna obtusifolia)
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Two of the successful herbicides (Conqueror® and Grazon Extra®) and rates are those already listed on PER82158 for the post-emergent control of sicklepod.
There may need to be variations in applied volumes and possibly methodology of application to get best pre-emergent results.
Sicklepod (Senna obtusifolia)
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As an example, Grazon
extra® could be applied
in the dry season at
relatively low volume to
the bare soil between
senesced plants.
Field use of pre-emergent: bare soil
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Or as a higher volume application to younger, greener plants to run off leaves and reach the soil surface. This would have the dual effect of killing both existing plants and their potential progeny.
Field use of pre-emergent:
plant cover
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Future work
Use of pre-emergent herbicides may be adapted to many other species in many other situations where weeds are inaccessible at important lifecycle stages.