NQ DRY TROPICS WEED FREE pg . 59
PARTHENIUM WEED
Parthenium hysterophorus
DESCRIPTION
This is an annual herb which grows to 1.5 metres . Stem is erect with distinct ribs . It becomes woody and develops branches in its top half when mature . Leaves are pale green , deeply lobed and covered with fine , soft hairs . Leaves are arranged on alternate areas of the stem . Flowers are small , diamond shaped and creamy-white in colour . It flowers during spring , summer and autumn . Seeds of 4 to 5 are contained in each flower . They are small and black seeds that are wedge shaped with 2 thin , white scales . Habitat this species colonises weak pastures with sparse ground cover . It grows in most soil types but becomes dominant in alkaline , loamy soils and on river banks , particularly where vegetation has been overgrazed . Weed characteristics are allergic reactions when contact with the plant or the pollen occurs . Its presence reduces the reliability of improved pasture establishment and reduces pasture production potential . Dispersal seeds can spread by water , vehicles , machinery , stock , feral and native animals , and in feed and seed .
BIOSECURITY MATTER
Restricted . This species is Category 3 Restricted matter under Queensland Legislation . This species is also listed a Weed of National Significance ( WONS )
HOW TO ACT
Spraying with a selective broad leaf herbicide prior to seed set is recommended . Improved grazing practices that minimise disturbed bare ground and maximise competing grasses are essential . Fencing areas to prevent stock movement while spraying will reduce further spread . Hand removal of individual or isolated plants prior to seed set is effective . Ongoing monitoring for up to seven years for emergent seedlings is recommended .
FORBS PARTHENIUM WEED