It isn’t often the words ‘hero’ and ‘bug’ get mentioned in the same sentence, but in this article we are going to be giving (some) creepy crawlies the credit they deserve. We will be discussing some of the thankless work these ‘hero bugs’ are getting up to on the Central Coast.
Alligator Flea Beetle (Agasicles hygrophila)
Alligator Weed (Alternanthera philoxeroides) is an invasive aquatic plant native to South America. In Australia it is a declared Weed of National Significance (WONS), but because of its adverse impact to both the economy and environment Alligator Weed is considered a significant threat globally. It is suspected that Alligator Weed was possibly introduced to Australia via the Newcastle area through cargo ship ballast water in the Second World War.
Alligator Weed is a challenge to treat, with freshwater bodies and wetlands especially vulnerable to invasion… but never fear, Alligator Flea Beetle is here!
The Alligator Flea Beetle (AFB) was first used in Australia in 1977 and has since been quite successful. Although not able to eradicate Alligator Weed, the AFB feed on the stem and leaves significantly reducing the floating mats formed by the weed.
On the Central Coast, at North Avoca, the AFB is successfully being used to manage Alligator Weed. Officers from Council’s Environmental Volunteer Program recently met with Council’s Biosecurity (Weeds) Officers to capture 60 beetles at the site, to then be released onto another site in Wyong where Alligator Weed is inundating an area. A monitoring area at the Wyong site has been set up to check if the Alligator Weed is being affected over time. If the AFB is successful in establishing at Wyong this may provide another donor site for more collections in the future.
Lantana Leaf Miner (Octotoma scabripennis)
Lantana (Lantana camara) is a prolific woody weed found throughout the Central Coast, inhabiting coastlines to wetlands, rainforests to ridgelines. It is difficult to drive anywhere within the local government area without catching at least a glimpse of this wretched weed. There is good news though, the Lantana Leaf Miner (Octotoma scabripennis) has been released and has a presence on the Central Coast.
The adult Leaf Miners feed on the upper surfaces of the leaves and lay their eggs within the feeding scars. When the eggs hatch the larvae feast in the middle leaf layers. In some areas of the Central Coast the Leaf Miner does exceptionally well, defoliating and stunting Lantana plants. This in turn reduces the ability of Lantana to flower and seed. The downfall, however, is there is a native wasp species that has taken a particular liking to preying on the Lantana Leaf Miners. We hope the Leaf Miners are able to knock out a few of the Lantana before the wasps in turn knock them out.
Bitou Tip Moths (Comostolopsis germana), Bitou Seed Fly (Mesoclais polana) and Leaf Roller (Tortrix spp.)
Like Lantana, Bitou Bush (Chrysanthemoides monilifera) has long since been a problem on the Central Coast, and more broadly throughout Australia. Introduced from South Africa, Bitou Bush was initially planted to revegetate dunes following sand mining activities. It takes over large areas, especially in coastal dune systems, outcompeting native plants and significantly affecting the health and biodiversity of the coastal dune ecosystem.
As a Weed of National Significance, a nationally coordinated approach to integrated pest management has been developed with nine biological agents approved for release in attempts to control Bitou Bush. On the Central Coast we have at least three of these, including Bitou Tip Moths (Comostolopsis germana), Bitou Seed Fly (Mesoclais polana) and a Leaf Roller (Tortrix spp.).
The Bitou Tip Moths and Bitou Seed Flys significantly reduce seed production and plant vigour reducing the ability of Bitou Bush to spread further.
The Leaf Roller shows promise as the most damaging insect to Bitou Bush, decimating stands of the weed. In high densities of Bitou Bush the larvae of the Leaf Rollers feed preferentially on shoot tips, reducing growth of the plants. As the larvae mature, they move to feeding on the older leaves of the plants.
Given Australia’s chequered history with biological control (think cane toads), it is only natural to be a little cautious in applauding the work these ‘hero bugs’ do. However, no longer are the days of haphazard release. The approval process is cutting edge science with stringent testing and controls. In particular, there are strict quarantine and trials to ensure crops and off target species, like native plants, are not adversely impacted well before any bugs are released.
Whilst handy in treating weeds, these biological controls are not magic bullets. They are used in conjunction with other treatment methods through an integrated approach. Typically, biological control is used to slow fruiting, strip foliage, reduce seed production and stunt the health of a plant. Biological control will never eradicate a weed, but they can certainly help in managing them.
If you have an area of dense weed and want to know more about biological controls, get in touch with your Environmental Volunteer Program Officer or send us an email at environmentalvolunteering@centralcoast.nsw.gov.au
This article was written by Jenna Markwick, Council’s Environmental Volunteer Officer with information provided by Paul Marynissen, Council’s Biosecurity Officer Weeds.