This trip the focus was again on the invasive weed Abrus precatorius subspecies Africanus (Common name – crab’s eye). The control program began in March 2014, with four trips a year since then. The population was extensively established on the Northern, Western and Southern sides of the village, as well as throughout the village area. It has not been detected East of the village. The plant is a creeper/climber, and in many areas, had occupied up to 70% to 80% ground cover and extended into the canopies of trees. It seeds in all areas where it grows, and profusely when it gets high levels of sunlight exposure, such as on the dingo fence and especially where it extends into the canopy of trees.
After trialling physical removal, including attempts to dig the roots out, and cut and paste with roundup, it became very clear these methods were ineffective and, given the extent of the infestation, were completely impractical. Foliage spray was trialled with glyphosphate and starane. Both chemicals resulted in good knock down of foliage, but with starane, plants regrew from the roots. Glyphosphate (1.5% Roundup) applied with a wetting agent and a dye is the mix we now use. It is extremely effective.
The volunteer teams collect seeds every trip. The seeds persist on the plants for long periods, often well in excess of a year, so minimising seed set is a high priority. Although there is no information in the literature about the seed’s viability, given the hard seed coat, it may remain viable in the soil for a considerable time. A germination trial commenced in March 2016, with 1000 seeds to better understand the viability of seed. The trial is not irrigated receiving only natural rainfall. Seedlings are counted and removed at the end of every month. By the end of April 14.9% had germinated. By the end of August, this had increased to 18.9%. So, 80.1% remain in the soil, either infertile or fertile and waiting to germinate. The trial is ongoing.
FIDO’s original aim was to work at the extremities of the infestation and contract it back to the village area. The team believes they have identified the extremities and imposed a very high level of control throughout the population. High priority has been given to eliminating mature plants and preventing further seeding. Most targeted areas are now all but Abrus free. The population is below 5% of that at the start of the program, probably below 1%, and seed set this season will be well below 1% of that in previous seasons. However, since there is a large load of seed in the soil, follow up inspections will be essential.
The area between Yidney Rocks Bypass Road and the beach is the last area of major concern. The area contains some very steep dunes and is heavily infested with Lantana and Easter Cassia making access extremely difficult. For the next trip, plans are to start work on eradicating these two invasive species from this area. This will also assist with locating and eradicating the remaining Abrus.
Peter Shooter, FIDO Project Officer (Happy Valley)