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Effect on animals
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More info?
│ Control
methods │Using
pesticides │Disclaimer
  One
of our most serious noxious
weeds, St John's wort (Hypericum perforatum) threatens all properties in northern
New South Wales. One plant of St John's wort can produce 30,000 seeds. The
(sticky) seeds are spread by animals, and the seeds can remain viable in the
ground for many years (anecdotal reports say up to thirty years). So, it only takes one plant to start a major
infestation!
Our main
infestations are in the Gulf Creek, Bingara, and Inverell
areas. Click on the map for a snapshot of the approximate extent of St
John's wort in the local district.
 Early detection and
treatment, before plants set seed, is critical. Unfortunately, St John's
wort is very difficult to find until the bright, yellow-golden flowers start to
appear. The first plants will start to set seed within two weeks. Two or three
treatments are necessary to be able to find and treat all plants.
Depending on the season, the flowering
period can extend from October to April.
Click on these photos to see the impact
 St John’s wort can have on grazing
land: two  separate properties near Inverell NSW Jan 2002 prior to
treatment. In these examples the owners can expect recurring seedling
growth for many, many years! It is essential that herbicide treatments are
followed up with sowing of competitive pastures. Liaise with your local
agronomist!
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EFFECT ON ANIMALS
 Over-exposure
to St John’s wort
can cause various animal health problems, including photosensitization. These
photos show the effects of St John’s wort on a horse that had been grazing in a
paddock of wort for only five days. Humans can be badly affected
by excessive contact with St John's wort. [photos - Ian Davidson, Inverell]
Click on
photos to go to a larger view…
IDENTIFICATION
  Apart
from the distinctive flowers (right), a
positive way to identify St John’s wort is by close examination of the leaves.
Hold a leaf up to the light and
(if your eyes are good enough) you will see what look like tiny pin holes
through every leaf. These are the hypericum oil glands.
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CONTROL
METHODS
Non-Chemical Options:
Perennial pastures and grazing management will offer some control (for details
see NSW DPI Agfact referred to in “More Information” below).
Converting an infested area
to a well-worked cultivation paddock is probably the only effective way to
eradicate St John's wort.
Chemical options for St John's wort:
According to NSW DPI’s
excellent booklet “Noxious and Environmental Weed Control Handbook 3rd
Edition”, treatments for St John's wort include:
|
Chemical options |
Rate: Spot/Boom |
Comments |
|
Triclopyr
600 g/L
+ picloram 600 g/L
eg Grazon DS® |
500 ml in 100 L of water
Boom rate: 2.0 – 4.0 L per hectare: |
Late spring to early summer, during flowering to early
seed set.
Apply November to January, use higher rate on dense infestations. |
|
Fluroxypyr
200 g/L
eg Starane® |
500 mL per 100 L water
3.0 L/ha |
Spring to mid summer application.
Boom application. Observe withholding period |
|
Glyphosate 360 g/L
Various trade names |
3.0 L per hectare |
Apply November to May, flowering to post flowering. |
|
2,4-D ester
600 g/L
Various trade names |
3.7 to 5.3 L per hectare |
For use in grass pastures, before flowering,when the
plants are les that 40 cm high. |
|
Glyphosate
835 g/kg + metsulfuron methyl 19 g/kg
Trounce® |
1 measured pack (173 g) per 100 L water |
Actively growing from spring to summer |
|
Metsulfuron methyl
600 g/L
eg Brushoff ® + glyphosate 360 g/L various trade names |
10 g metsulfuron methyl PLUS 200 ml glyphosate per 100 L
water |
Spray to wet, but not to cause run-off. |
IMPORTANT:
USE OF PESTICIDES – ALWAYS READ THE LABEL
Pesticides
must only be used for the purpose for which they are registered and must not be
used in any other situation or in any manner contrary to the directions on the
label. Never use a herbicide in any way contrary to the label recommendations.
MORE INFORMATION:
Detailed St John’s wort information (a 12-page Agfact) is available on the
NSW DPI Weeds
Sub-Program website (PDF format - large document, takes some minutes to
download but worth the wait!). Another excellent reference is the book "Noxious Plants of Australia", by Parsons and Cuthbertson
[Inkata Press].
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DISCLAIMER: The information contained in this
web site is based on knowledge and understanding at the time of writing.
However, because of advances in knowledge, users are reminded of the need to
ensure that information upon which they rely is up to date and to check currency
of the information with the appropriate officer of North West Weeds or the user’s independent adviser.
LRT 17/10/062002
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North West Weeds
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