Impacts of serrated tussock

Serrated tussock is a highly invasive weed of temperate Australia. It is one of Australia’s worst weeds and was selected as a Weed of National Significance due to its invasiveness, potential for spread and social, economic and environmental impacts (Thorp and Lynch 2000).

Being similar in appearance to many native tussock grasses, serrated tussock may go unnoticed in both pastures and native grasslands for many years until significant infestations have developed.

It will readily invade pastures, native grasslands, grassy woodlands and roadsides. Being a weed that is mostly dispersed by wind, it will easily spread between paddocks and properties within a region. Serrated tussock is a weed that can cause many complex issues within the communities that it occurs, requiring long-term management and a community/regional approach.

Serrated tussock can have significant impacts on agriculture, native grasslands, and urban environments.

Serrated tussock infestations will reduce the carrying capacity of the pasture - Source: DEPI Victoria 

Agriculture

Serrated tussock is an invasive weed of pastures, having the potential to infest entire properties. It has been described as causing a greater reduction of pasture and grazing carrying capacity than any other weed in Australia.

Pastures that can normally carry 7–15 dry sheep equivalent (DSE) per hectare can be reduced to a carrying capacity of only 0.5 DSE per hectare if heavily infested with serrated tussock (Campbell and Vere 1995). In NSW alone, it is estimated that serrated tussock has cost more than $40 million per year in control and lost production and $5 million per year for its control in Victoria.

Serrated tussock is unpalatable to livestock and will only be eaten if nothing else is available. It is of low nutritional value to livestock, with plant digestibilities in the range of 30% to 51% and metabolisable energy levels ranging from 4 MJ/kg DM (megajoules per kilogram of dry matter) to 7 MJ/kg DM. Any feed of this quality is insufficient to meet livestock requirements. If livestock are forced to graze pastures containing only serrated tussock, the leaves can form indigestible balls in the rumen, causing a loss of condition and eventual death.

Serrated tussock seed is a contaminant of hay, can remain viable in the gut of livestock for up to 10 days, and can attach to vehicles, machinery, and equipment. All of these mechanisms have the potential to spread serrated tussock over long distances.

Serrated tussock can reduce the biodiversity values of native grasslands. - Source: Steve Taylor 

Native Grasslands

Native grasslands are one of Australia’s most threatened ecosystems. Less than one per cent of their original extent remains (Ross 1999) and these are in various stages of degradation throughout south-east Australia. Two native grasslands communities have now been listed as endangered under the Commonwealth’s Environment Protection and Biodiversity Conservation Act (1999) — 1. The Victorian volcanic plain temperate grasslands and 2. The natural temperate grasslands of the southern tablelands of New South Wales (NSW) and Australian Capital Territory (ACT).

Often high quality native grasslands are small, remnant areas occurring where human land use has not had a significant affect. Serrated tussock is a key threat to native grasslands. Being very similar in appearance to many of temperate Australia’s native grasses, it is able to go unnoticed in grasslands for many years. Unfortunately by the time it is recognised, the native grasses have been replaced by significant infestations of serrated tussock.

Serrated tussock has already invaded many of temperate south-eastern Australia’s most endangered native grassland remnants and its presence is a serious threat to the native flora and fauna of these grasslands.

While serrated tussock is mostly a problem reducing the biodiversity values of native grasslands, it can also invade other environmentally significant areas such as dry coastal vegetation, grassy woodlands and sclerophyll forests.

Large infestations of serrated tussock can cause a fire risk. - Source: Bronwen Wicks

Urban situations

Roadsides, parks, neglected areas, railways, power line easements, reserves and sporting grounds are all areas where serrated tussock can be a weed in cities and towns. These areas can be a source of seed spread by wind, vehicle movement or maintenance activities such as slashing. Some of these areas may also contain or be adjacent to remnant native grasslands.

Large build-ups of serrated tussock are a concern in urban areas because of the increased fire risk and hazard because:

• fire intensity is increased due to the dryness and large biomass of combustible material in serrated tussock
• seed heads can catch fire and then blow away, capable of starting fires some distance away
• seed heads can be blown up into the eaves of homes
• the fire season is lengthened in areas where large infestations occur.

The seed of serrated tussock may also be spread throughout urban areas by mud on the hooves of horses, by sticking to the coats of pets, or by human movement or activities.

This information can be found in the in the National Serrated Tussock Best Practice Manual.