Everyone will be familiar with that bright green groundcover with the dainty yellow daisy flowers. Singapore daisy was introduced to Australia in the 1970’s as a garden plant, today it has become the cane toad of the plant world, in particular tropical regions throughout the world.
Singapore daisy, despite its name, is actually a South American plant.
It is a “prostrate vine” – meaning that it spreads by means of “runners” which can extend for tens of metres along the ground under appropriate conditions. The runners have nodes, and each node bears two characteristically-shaped leaves, as well as producing roots, which, should any damage occur to the runner, are capable of creating new plants. Under good conditions, these runners can extend a meter per week. Fortunately for us, it hardly ever produces seed, despite the masses of flowers, and the seeds it produces are seldom fertile.
Its ubiquity and rapid rate of spread has given rise to the belief that it cannot be controlled, and attempts to control it using herbicides such as Roundup (glyphosate) have been totally unsuccessful.
Singapore Daisy is also allelopathic – which means that it suppresses the germination of other plants. This is why you rarely see other plants (unless they have been established before the invasion) growing in a Singapore Daisy infestation.
The herbicide that environmentalists are happy to use
In 1983 a herbicide was developed with the active ingredient Metsulfuron Methyl, this active ingredient has very low toxicity to mammals, birds, fish and insects. It was hailed as a game changer for control of broadleaf weeds in cereal crops. Today it is known as ‘MSM’ for short.
Metsulfuron-methyl is rapidly taken up by plants at the roots and on foliage. The chemical is translocated throughout the plant, but is not persistent. In tolerant plants, it is broken down to non-herbicidal products.
Metsulfuron-methyl has very low toxicity in mammals. Systemic poisoning is unlikely unless large quantities have been ingested. The chemical is broken down quickly and eliminated from the body.
Metsulfuron-methyl is not carcinogenic, it is neither mutagenic nor genotoxic. It is not classified as a poison in the Standard for the Uniform Scheduling of Drugs and Poisons.
Metsulfuron methyl is very effective against Singapore Daisy and other broadleaf weeds with the bonus that it affects very few native plant species.
The 30 year patent on this herbicide expired in 2013, before then MSM was prohibitively expensive to buy. Today it is one of the cheapest and safest herbicides to use.
It is a granular product, which is used in conjunction with a wetting agent, to ensure that it wets the leaves. You require very little 1g per 10 litres of spray. The wetting agent is usually 1 ml/litre of spray. Cost of MSM for 10 litres of spray is only 8 cents.
The herbicide is translocated by Singapore Daisy, which means that the root system gets killed as well. RoundUp or Glyphosate kills everything and does not translocate well with Singapore daisy, it brown’s off but the roots are not killed completely.
3 weeks after spraying an infestation with MSM the majority of plants will be completely dead, a follow up spray should occur 10-12 weeks later for plants missed and then a 6 monthly inspection should occur. Regular “spot spraying” of re-sprouts and seedlings is essential, although the plant does not produce many viable seeds.
The Daintree region has a program where the herbicide and wetting agent is available to people wishing to help rid the weed from the beaches and waterways in the region. The BBPA is investigating how a similar program can be developed for Bramston Beach.