Home » Biocontrol » The Persistence of Abrus

The Persistence of Abrus

One of FIDO’s many inspiring volunteers has been Peter Dorney, a nurseryman from Boreen Point.  Pete was appalled by the extent and aggressiveness of the rampant Abrus he encountered during a Happy Valley working bee in March 2016.  He wondered how persistent the seed might be because this is critical to how long the vigilant treatment of Abrus needs to be maintained once no more seeds are set. 

Abrus

One year’s seed – how many years of weed?

This inspired him, with meticulous nurseryman’s methodology, to take some seed home and set up a number of trials.  Pete had two aims:

  1. To test the seed viability of mature seeds from dehisced pods, and to determine the length of time they remain viable and thus whether they exhibit delayed germination.
  2. To test the viability of immature seeds from unopened pods to see whether it is important to remove and destroy these pods from the vines.

One trial involved planting out 1,000 mature seeds (collected in March) in an area getting some daily sun and some shade and relying on natural rainfall only.  He has since counted and removed germinated seeds each month.  At the end of April, 14.9% of these seeds had germinated.  There was little additional germination during winter and by the end of September 19.8% had germinated.

Simultaneously, Pete has been conducting other trials such as testing germination under more ideal conditions and testing the viability of seed from unopened pods and of slightly less mature seeds.  He has also planted out some seedlings to see how long they take to flower after germination.  His reports have been regular and revealing of the behaviour of Abrus seeds.  While Pete’s trials are yet to run a full year, they indicate that Abrus management at Happy Valley might need to continue for years.

Peter Dorney’s enthusiasm prompted Su Dawson to pursue her own trial.  When working in Happy Valley

in 2013, she accidentally carried a few Abrus seeds back with her.   She had put them away, but was reminded of them by Pete’s trials.  She found two seeds and put them into a small pot of potting mix to see what would happen.  In April 2016, one of the seeds germinated.  She decided to leave it to grow to see what might happen.  There was little growth of the seedling, which had little ‘soil’ to support it.  It did though get supplementary watering.  At the end of November, it grew more rapidly, doubling its size in just a few weeks.  In early December, she noticed that the second seed had belatedly germinated in this small pot.  Like Peter Dorney, she is waiting to see how long the plants take to set flowers.  It seems that Abrus is very responsive to warmer weather and longer days.

These citizen science trials are helping to shape FIDO’s strategy to eliminate this very nasty weed from K’Gari.  By November 2016, most of the old Abrus known in Happy Valley had been killed, except in the more residential area.  Peter Shooter and his various teams will continue to closely monitor and deal with any new germinants, to stop them flowering and setting any more seeds. However, his weeding teams can now turn their attention to deal with other weeds.  Removing the larger ecology-changing Lantana and Easter Cassia will also make it easier to access and monitor some of the areas where Abrus was once thick.

Article contributed by John Sinclair, AO, FIDO


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