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Rubber vine, the dark towering shrubs above,
infests thousands of hectares in Queensland. Photo: Kate
O'Donnell
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New research has found a loophole in the
biology of rubber vine that will help in the fight to contain the
weed
Researchers at the Tropical Weeds Research Centre, located at
Charters Towers, have found that the exotic weed rubber vine lacks
a persistent seed bank—under normal rainfall conditions,
seeds live in the soil less than 12 months. Even though seeds will
survive up to two years or longer under drought conditions, the
weed contrasts markedly with other weeds such as prickly acacia,
mesquite and parthenium, whose seed bank can survive for many
years.
Fresh rubber vine seeds, which fall to the ground after maturing
in pods on the plant, were found to be highly germinable. This
means that virtually all seeds will germinate and develop into
seedlings if they receive sufficient moisture. This is unusual for
weeds, as many have a mechanism that prevents all seeds from
germinating at once. Prickly acacia and mesquite have a hard seed
coat that has to be broken down before seeds will germinate, which
means some seeds will survive for many years even if there is a
great deal of rain. Parthenium, for example, has a seed bank that
will last more than eight years.
This is potentially a major weakness of the plant, and provides
an opportunity for land managers to contain the widespread weed.
Rubber vine infests thousands of hectares in Queensland,
establishing itself along riverbanks and creek lines, and has the
potential to spread to other areas of northern Australia.
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Rubber vine leaf under attack by rust. Photo:
Greg Calvert
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Rust pathogen
An introduced rust pathogen has proven very effective in
reducing the amount of seeds the plant produces. When there is
adequate moisture to help the rust spread and work effectively, the
number of pods in an area will be greatly reduced. If the rust has
been present for a couple of years, and there has been a normal wet
season, the rubber vine soil seed bank will be very low. Under
these circumstances, if control activities are performed to kill
the initial infestation, seedling regrowth should be minimal.
However, in areas where the rust is not effective (such as
around Hughenden and some areas of the lower Gulf) or in locations
which have experienced a number of dry years that have prevented
the rust from re-establishing, it is likely that large numbers of
live rubber vine seed will be present. Eradicating rubber vine in
these situations is much harder as substantial seedling regrowth
may occur even following control activities. Nevertheless, because
the seed bank is so short-lived, follow-up control should only need
to be undertaken for one to two years after the initial infestation
has been treated.
