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Identification
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The problem
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Locality Map
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Control methods
│Using
pesticides │Disclaimer
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  Harrisia cactus (Harrisia
martinii) is a native of the Americas, no doubt introduced into Australia
for its appeal as a garden plant. Harrisia became a serious pest problem in
parts of Queensland, eventually spreading into the Boggabilla-Yetman areas of
New South Wales.
Harrisia cactus is spread
by seed. The plant can begin to produce seed at age 6 months and from then on
can continue to produce fruit almost all year round. Each fruit contains about
800 seeds encased in a sweet, sugary substance which is extremely popular with
birds, emus and pigs.
 Harrisia
cactus has continued to spread into various parts of north-west New South
Wales. The sharp spines are something of a hazard to humans and animals.
Harrisia is hard to control because of its seed-producing ability. Birds and
foxes carry the seed for miles. Goannas and ants also enjoy the sweet
fruit. Most seeds seem to germinate. [Click on
photos for a closer look at typical harrisia plants]
IDENTIFICATION
  Harrisia cactus is a
low-growing, jointed, cactus plant. Its runners spread out like the tentacles
of an octopus. When the runners touch the ground they take root. The
fruit – about “passion fruit-size” – is bright red when ripe. It splits
open to reveal sweet seeds to birds, animals and ants.
THE PROBLEM
Harrisia cactus can cause
painful injury to animals or humans who accidentally walk into or otherwise
touch a plant. It is a prolific seeder, spread s quickly, and has the ability to
eventually take over large areas of grazing country.
CONTROL METHODS
Ploughing
is probably the only means of eradication. Harrisia cactus cannot survive on
lands under constant cultivation [NB State laws apply in respect of land
clearing.]
Burning
Not a practical option - tops of plants are easily killed, butts go deep
into the ground and therefore require extra heat. Burning is really
 only
appropriate for small infestations. Follow up always required [NB Subject to compliance with local
bushfire restrictions].
 Biological control
using a mealybug (Hypogeococcus festerianus) has been effective in warmer
areas of Queensland but results in northern NSW have been disappointing. It
is of some limited use in thick infestations only and is not recommended
for isolated plants. When working well, the mealybug impedes growth, but
plants will still bear fruit and continue to infest surrounding areas. Insects have to be
manually transferred into uninfected plants - the mealybug does not have the capacity to spread as efficiently
as do new seedling plants. The seeds can be spread kilometres by birds and
animals, whereas the mealybug can only travel a matter of metres. And,
cactoblastis
or cochineal are
TOTALLY INEFFECTIVE on Harrisia cactus.
Chemical treatment
is effective, but must be regularly undertaken. According to NSW DPI’s
excellent booklet “Noxious and Environmental Weed Control Handbook
3rd Edition” plus information from new permit 10544, herbicide treatments registered for use in New South Wales
include:
|
Chemical |
Rate |
Comments |
|
Triclopyr 240 g/L + Picloram 120 g/L
Access® |
1.0 L in 60 L diesel |
Folia application. |
|
Dichlorprop 600 g/L
eg Lantana 600® |
(1L/60 L water) |
Good soil moisture essential and spray at fruiting. |
|
Metsulfuron-methyl 600g/L Various trade names |
20 grams in 100 L water plus wetter |
Spray to thoroughly wet plant. Add a surfactant. |
|
Triclopyr 300 g/L + picloram + Aminopyralid 8 g/L
eg Grazon Extra® |
High volume 500 ml in 100 L water + 5% Uptake spray oil
(2011
herbicide trials indicate best results 250 mL in 100 L water – lower
rate allows translocation into root system before top of the plant shuts
down – Webmaster Oct 2011).
See STOP
PRESS below |
Apply to actively growing plants - see APVMA
permit
PER 10544
for more details
(in force until 30 June 2013). |
|
Triclopyr 300 g/L + picloram 100 g/L
eg Grazon DS® |
NB Most Harrisia cactus in
New South Wales is found near the border with Queensland, mainly in the
Boggabilla - Keetah - Milkomi area. For those NSW property owners who also have land north of the
border, please note that there are a number of other herbicide options registered for use in
Queensland only, including triclopyr as tea(200g/L) + picloram as
tipa(100g/L) eg Tordon DSH®
(2.5 L/100 L water). Check labels for
full directions.
 MORE
ON HERBICIDES - UPDATED 5 JUNE 2011:
Over the past 18 months,
Inverell Shire Council has been running herbicide trials on harrisia cactus in
the far northern part of the Shire, near the Queensland border). The trials are
continuing, but at this stage the following observations have been made:
(1) 20g metsulfuron methyl plus 100mL wetter to 100L water is very effective,
especially for large infestations because this mixture is so inexpensive - less
that 3
cents a litre [see
before and after photo]. One down-side is the possible risk to desirable timber, although
very little damage was observed during the trials or in other major contract
spraying jobs carried out during this period.
(2) The standard Grazon-type herbicide
(Triclopyr + picloram)
mixture of 500 mL per 100 litres water appears to be TOO
STRONG, taking out the top of the plant before translocation into the root
system, therefore leaving the way open for excessive regrowth.
(3) Grazon (or equivalent in other brands) herbicide appears to work consistently well when applied at
250 mL plus
500 mL uptake oil per 100 litres of water. Cheaper than full-strength Grazon
(@12c litre) - minimal re-growth, minimal damage
to trees, grass and other desirable/off-target species.
 STOP
PRESS! I had a quick look at these trials on Friday 18 November 2011.
The Grazon has FAILED. everywhere - some still showing effects of the herbicide
so it may yet have a secondary impact on the plants? The season has been good
and there are many new plants as well... I will check out the trials and
report on the results with more detail over the next several weeks - webmaster.
See photo right - ..
(4) Trials of dichlorprop 600 L. were very disappointing; excessive
re-growth and very costly at about $2.20 litre. I have photos...
(5) More information on these trials: contact the webmaster at
northwestweeds@aapt.net.au
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
Queensland Department of
Primary Industries has had a long involvement with managing this predominantly
Queensland cactus… see their informative webpage
http://www.dpi.qld.gov.au/4790_7297.htm
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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 31/08/09
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North West Weeds
