Technical highlights - Department of Primary Industries ...

7. Evaluating the effectiveness of the EZ‑Ject herbicide lance
Project dates
December 2007 – December 2010
(completed)
Project leader
Joseph Vitelli
Ecosciences Precinct
Tel: (07) 3255 4473
Email: joseph.vitelli@deedi.qld.gov.au
Other staff in 2010–11
Barbara Madigan
Objective
Evaluate the effectiveness of the EZ-Ject TM
herbicide lance in controlling woody weeds
in Queensland using both glyphosate-filled
and imazapyr-filled shells.
Rationale
Using the EZ-Ject herbicide lance is a
relatively new technique for the control
of woody plants by stem injection. The
stainless steel lance has gripping teeth
at the end and a spring-loaded assembly
that injects .22 brass shells filled with
water-soluble herbicide into the cambium
layer of woody plants. No mixing of, or
contact with, the herbicide is required
by the operator. The longer version of
the lance (1.5 m) holds up to 100 shells
in each of four separate shell chambers.
The shells are implanted at a downward
angle evenly around the circumference
of the base of the plant. Two herbicides
(glyphosate and imazapyr) are registered
for use with the lance in the United
States and Canada. Plants may be
injected at any time of the year and may
be standing in water or wetlands, though
the injection site should be above the
water level.
To trial this control method, three
woody weeds were chosen, each from
a different family and each infesting a
different area of Queensland. Captain
Cook tree (Cascabela thevetia), family
Apocynaceae, is a Class 3 weed that
is highly toxic and invades native
vegetation. Velvety tree pear (Opuntia
tomentosa), family Cactaceae, is a
Class 2 weed found predominantly in the
brigalow belt of Queensland. Pond apple
(Annona glabra), family Annonaceae, is
a Weed of National Significance (WONS)
and a Class 2 weed. It can grow in
flooded areas of fresh, brackish or salt
water, forming dense thickets capable of
replacing existing ecosystems.
If effective and subsequently registered
for use in Queensland, this tool would
help the operator avoid direct contact
with both the herbicide and any thorns
or spines on the plant. The technique
would be particularly useful in wetlands
and other sensitive environments,
allowing treatment of individual plants
without affecting surrounding native
vegetation or contaminating waterways.
Methods
Captain Cook tree near Mingela, velvety
tree pear near Inglewood and pond
apple near Babinda are treated with
the EZ-Ject herbicide lance in split-plot
design experiments with the herbicide as
the main plot (glyphosate and imazapyr)
and the number of cartridges as the subplot
(0, 1, 2, 3 and 4 shells). We replicate
each treatment four times and the
experimental unit consists of 15 plants.
All treated plants have a basal diameter
of 10–15 cm. We assess plants 1, 6
and 12 months after treatment using a
damage-rating scale and determine plant
mortality at the final assessment.
Findings
This study established that the EZ-Ject
herbicide system is an effective tool for
controlling individual woody plants,
although the degree of control varied
among species, with efficacy influenced
by herbicide and number of cartridges
injected.
Cartridges filled with imazapyr were
significantly more effective than those
filled with glyphosate at controlling
the three woody weed species. Injecting
plants with three imazapyr cartridges
resulted in mortalities of 93–100%,
compared to mortalities of 17–100% for
glyphosate cartridges. Pond apple was
the most susceptible species, requiring
one imazapyr cartridge to kill 97% or
two glyphosate cartridges to kill 92% of
treated plants. Plant mortality increased
as the number of cartridges injected
increased. However, mortality did
not differ significantly for treatments
receiving three and four imazapyr
cartridges, as the lower cartridge
density already met the manufacturer’s
recommendation of injecting one
cartridge per 10 cm basal circumference
when treating large plants (> 6.35 cm
diameter at breast height).
Photo 7.1 Bullets of water-soluble herbicide injected into the base of woody weeds
Part 1 Integrated weed management 17