Landholders are encouraged to keep an eye out for St John's wort as the weed is spreading through the region.
Central West Local Land Services mixed farming adviser Callen Thompson said there were known infested areas around Coolah, Merrygoen and east of Coonabarabran but in the last two years there had been a marked increased of it spreading throughout farms, lifestyle blocks and bushland.
Mr Thompson said the weed spread easily and was poisonous to livestock.
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"It contains a chemical called hypericin, which causes photosensitivity. Other symptoms include weight loss, stillbirths and in severe cases, death. Young stock are more susceptible, with suckling stock still effected through the milk of their mothers," he said.
"St John's wort will compete with pasture species and can also create a vegetable fault in wool."
Pulling out the St John's wort is not enough to destroy it. Isolated plants or patches of plants can be controlled by spot spraying with a registered herbicide. Larger areas can be sprayed with a boom spray.
"It is important for all land holders to be vigilant, learn how to identify it and control it as soon as they see it," Mr Thompson said.
If you would like help identifying St John's wort, contact your local councils weeds officer or Mr Thompson at LLS on 0417 348 687.
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