Pests

The Problem with Rubber Vine

Rubber vine is a vigorous climber which can grow either as a many stemmed shrub 1-2 meters in height, or scrambling up to 30 meters in trees. It was introduced into Australia as an ornamental shrub during the 1800s. Rubber vine spreads through seeds borne by water or wind. It invades riparian vegetation along waterways hillsides and pastures and is poisonous to stock if eaten.

Rubber Vine is a Weed Of National Significance and is also Restricted Matter – Category 3 under the Biosecurity Act 2014. This means that it cannot be distributed or disposed of in any way.

The Rubber Vine plant

• Rubber Vine stems, leaves and unripe pods expel a milky sap when broken or cut.
• Leaves are in opposite and dark green, glossy 6-10 cm long and 3-5 cm wide.
• Flowers: five petals ranging from white to light purple in colour arranged in a funnel shape.
• Seed pods 10-12 long, ridged and grow in pairs at the end of a short stalk.
• The seed pods contain 450 brown seeds. These seeds each have a tuft of long white silky hairs.

Case Studies

• Rubber Vine Case Study

References

• Qld Department of Agriculture and Fisheries rubber vine fact sheet

The Problem with Pond Apple

Pond Apple (Annona glabra) is a major weed impacting areas in northern Queensland. Pond Apple was originally imported to Australia in 1912 as root stock for Custard Apple. Unfortunately its invasive nature was not realised until it was found growing in dense clumps in mangrove systems in Northern Queensland. Scattered dense infestations occur along the eastern coast and the tip of the Cape York Peninsula.

The potential distribution of Pond Apple includes north Western Australia, the top end of the Northern Territory, the Gulf of Carpentaria, Torres Strait Islands, and along coastal areas along the eastern coast of Australia from Cape York to northern New South Wales.

During 2008 a pond apple infestation was located in Andergrove, a northern suburb of Mackay and again in 2009 a fruit was brought to the attention of local biosecurity officers. The fruit was collected from a tributary creek within the Reliance Creek Catchment also just north of Mackay. Upon identification an extensive search was carried out to identify the extent of the infestation.

Pond Apple is a small to medium tree that threatens mangroves, rainforests, and drainage systems including; creeks, river banks, coastal dunes and wetlands. Seed are spread primarily by water and have a high potential to be spread by animals including the southern cassowary and feral pigs.

This species is a Weed Of National Significance and is also Restricted Matter – Category 3 under the Biosecurity Act 2014. This means that it cannot be distributed or disposed of in any way.

The Pond Apple Tree

• Young Pond Apple Tree: the typical height is 3-6 metres; however they can grow up to 15 metres.
• Pond Apple is a soft wooded, semi-deciduous tree. This tree has a light grey bark with conspicuous lenticels.
• The petals are a pale yellow to cream, with a red/pink inner base; 3 leathery outer petals, 3 smaller inner petals, 20-30 mm in diameter.
• Flower buds are green and hang down, making flowers difficult to see at times.
• The Leaves are alternate, simple, light to dark green, 70-120 mm long, prominent mid vain, distinct smell like green apples when crushed.
• The Fruit is round, and fleshy  5-15 cm in diameter, immature fruit is green ripening to orange –yellow and turning black after falling from the tree. 100-200 brown seeds similar in size and shape to pumpkin seeds.

Further information

• Pond Apple fact sheet
• Fact sheet

The Problem with Mimosa Pigra

Mimosa pigra is a thorny legume shrub with many branches that grows along waterways and invades freshwater wetlands and swamps. Originally from Central and South America, it was planted at the Darwin Botanic Gardens in the late 1800s as a curiosity. Its invasive nature was not realised until the 1950s when it was observed growing in drainage lines and creeks.

It forms dense, impenetrable thickets, 3-6 meters high. If left untreated Mimosa pigra has the ability to restrict access to water impacting on recreational activities, tourism, stock watering points, pasture quality and mustering.

The Northern Territory has the most extensive infestation of Mimosa pigra, which covers an approximate area of 80,000 ha. In 2001 a local landholder discovered Mimosa pigra growing at Lake Proserpine (Peter Faust Dam). This infestation is one of only two infestations found outside of the Northern Territory, the other being on the Western Australian/Northern Territory Border.

Mimosa pigra is spread via water, contaminated soil, vehicles, boats, boat trailers, animals and through suckering.

This species is a Weed Of National Significance and is also Restricted Matter – Category 5 under the Biosecurity Act 2014. This means that it cannot be kept.

The Mimosa Pigra Plant

• Flowers are light pink, round and fluffy balls generally 1-2 cm across.
• Each leaf is approximately 25cm long and has up to 16 opposite segments, which consists of segments 5cm long made up of opposite pairs of leaflets. These leaflets fold up when touched or at night.
• The thorns of Mimosa pigra resemble those found on a rose bush however on Mimosa pigra these thorns are much more numerous.
• The seeds are oblong approximately 4-5 mm by 2 mm in size encased in a brown hairy segmented pod 6-8 cm in length.
• Mimosa pigra seeds have an average seed life of 22 years.

References

• Drewry. J, Higham W, Mitchell. C 2008, Water Quality Improvement Plan: Final report for Mackay Whitsunday region, Mackay Whitsunday Natural Resource Management Group
• The State of Queensland, Department of Environment and Resource Management 2011, REED Regional Ecosystem Description Database

Further information

• Fact sheet

The Problem with Leucaena

Leucaena leucacephala is a large shrub, originating from Central America. In our tropical coastal area Leucaena leucacephala subspecies leucopehala has become a weed, invading creek banks, roadsides and mangrove margins. Experts advise that while the subspecies leucopehala is predominant, a number of other subspecies can be identified in the Mackay Whitsunday Region.

This specie, Leucaena leucacephala subspecies leucopehala, is often confused with Leucaena leucacephala subspecies glabrata which is widely grown in drier areas as cattle fodder. Due to the ability of this species to spread Leucaena leucacephala subspecies glabrata is grown under guidelines in a voluntary management agreement, designed to prevent spread out of managed pastures.

Leucaena leucacephala subspecies leucocephala is now a locally declared weed in the Whitsunday Regional Council boundaries.

The Plant

• Leucaena leucacephala subspecies leucocephala is a small tree growing up to 6 meters in height.
• It grows in dense clusters
• Pods are brown and flattened 5.5 to 17 cm long and 15 to 20 mm wide. These pods contain 5-24 glossy brown seeds.

Further Information

• Leucaena fact sheet

The problem with Itch Grass

Itch grass is competitive with annual crops and invades sugarcane, pastures, and roadsides. It is difficult to manage once established. Because of its size and vigorous growth, itch grass is competitor for sugarcane and heavy infestations can cause severe crop loss.

While sometimes described as unpalatable to livestock, grazing has shown to reduce incidence of Itch grass.

A single large plant can produce 2,000 to 16,000 seeds that are shed by the plant as soon as they mature. It is a significant weed in several crops including maize, sugarcane, upland and rain-fed rice, beans, sorghum and perennials such as citrus and oil palm at early stages of growth.

Itch grass has a single stem that is cylindrical, hollow and branches into sheaths at upper nodes. The stem and leaves are covered in stiff hairs that can cause irritation to skin. Itch-grass leaves are blue-green in colour in good conditions but often yellowish, flat, 5-20 mm wide with round edges and a conspicuous pale mid-vein. Flower heads are borne in pairs that branch out from the upper nodes and form green spikes about 10cm long. As the heads mature, the cylindrical rice sized seeds progressively break free from the end and fall to the ground. Itch grass seed is known to germinate after the first significant rain in summer.

The Problem with Hymenachne

Native to South America, Hymenachne was introduced as a ponded pasture grass for cattle fodder. However this plant is highly invasive invading lagoons, wetlands, rivers, creeks and table drains. It interferes with the function of irrigation, infrastructure, recreational activities and wildlife habitats. It is spread through seeds and stem fragments dispersed by water, waterbirds and contaminated stock feed.

This weed has the potential to be confused with the native Hymenachne, Hymenachne acutigluma. The difference is the exotic introduced species has a distinctive stem-clasping leaf base, where as the native Hymenachne does not. The native species is a smaller tropical species that does not grow south of Mackay.

Hymenachne amplexicaulis is a Weed Of National Significance and is also Restricted Matter – Category 3 under the Biosecurity Act 2014. This means that it cannot be distributed or disposed of in any way.

The Plant

• Hymenachne amplexicaulis is a perennial grass growing to 2.5 meters in height.
• The leaf sheath strongly clasps at base with the blades 10 to 45 cm in length by 3-6 cm wide. Hairy at the margins and has light coloured veins.
• The seed heads are 20 to 40 cm in length and are in a cylindrical, spike like arrangement.

References

• The State of Queensland Department of Agriculture and Fisheries Hymenachne or olive hymenachne fact sheet
• Fact sheet

The Problem with Giant Rat’s Tail grass

Like other weedy sporobolus grasses, Giant Rat’s Tail grass (GRT) is an aggressive competitor that can reduce pasture productivity and significantly degrade natural areas. Flowering plants are long-lived and can exist for more than 4 years. Their foliage has low palatability for animals when mature and is therefore not selectively grazed. GRT is resistant to fire, slashing, grazing and high competition. However, it is sensitive to some herbicides.

Seed is produced all year around, but mostly in summer and autumn. A large soil seed bank forms quickly and seeds can live dormant in the soil for approximately 8 years.

GRT grows to an average maximum height of between 1.7-2m, with the seed head growing to 45cm long and 3cm wide. These seed heads are often darker coloured and change from a rats tail shape to an elongated pyramid shape. They can be difficult to differentiate from other pasture grasses before maturity. The leaves are noticeably tougher than other sporobolus grasses and our native sporobolus grasses tend to be shorter, softer and have lower density seed heads than GRT grass.

Weedy sporobolus grasses are aggressive, have low palatability when mature, and are difficult to control. They can quickly dominate a pasture, especially following overgrazing or soil disturbance. Giant rat’s tail grass (GRT) poses a significant threat to the productivity of pastures in the Mackay Whitsunday Isaac region and being one of the weedy sporobolus grasses (WSG) it has the ability to significantly decrease grazier’s economic viability and degradation of natural areas. Cattle grazing GRT pasture take up to 12 months longer to reach equivalent weight. In 2007 the estimated cost of GRT and other WSG to the pastoral industry was $60 million per year (Bray and Officer 2007).

Seed germination and emergence requires an area of low competition, where pasture and other plants have been disturbed and a gap exists. Good pasture cover reduces emergence. Seeds can germinate all year round, but mostly in spring and summer.

The survival of early seedlings is sensitive to competition. Seedlings can flower within 3 months. Attempts to control this weed using conventional methods have often failed and, in some cases, intensified the infestation. Pastures dominated by GRT are common, due to the long-term viability of GRT seed in the soil and the tendency of stock to graze other more palatable pasture.

References

• Bray, S. and Officer, D., 2007, Weedy Sporobolus grasses Best Practice Manual, Department of Primary Industries and Fisheries, Brisbane

Further Information

• Department of Agriculture and Fisheries Fact Sheet
• Fact sheet