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The Problem
Paterson's curse is an introduced winter annual pasture weed
of Mediterranean origin. Free of native Mediterranean plant
and insect communities, it has become one of the dominant
pasture weeds of temperate Australia.
In Australia the weed produces 10,000's of seed by late
spring which sit dormant over summer
waiting for rain when they germinate in there 1,000's. The
seedlings grow quickly, develop a
large taproot making them resistant to drought and form a
flat rosette out competing other germinating
plant species. By spring it can completely dominate a paddock
resulting in the endless fields of purple
we see in spring each year.
Although relatively nutritious in terms of digestible nutrients,
and valued as a pasture plant in some places, Paterson's curse
contains pyrrolizidine alkaloids that are poisonous to livestock,
destroying the liver of the animal, reducing weight gain and
wool clip and in severe cases leads to death. Paterson's curse
was estimated to occur on over 30 million hectares in Australia
(in 1985) and cost the wool and meat industries $125 million
each year (in 2002).
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In spring 90% of the pasture can be Paterson's
curse producing up to 30,000 seeds per square
metre.
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Rosettes quickly dominate the bare ground in autum/winter
outcompeting other germinating plant species.
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Seeds (up to 30,000 per square metre) remain dormant
in the soil for at least ten years.
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Late summer/autumn rain stimulate germination and the
emergence of seedlings; up to 2000 per square metre.
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