Prolonged wet weather has the Castlereagh Macquarie County Council informing Warrumbungle Shire and surrounding landholders of the expected 'busy season' for St John's Wort.

Castlereagh Macquarie County Council Chairman Councillor Doug Batten urges Warrumbungle landholders to identify and control St John's Wort in order to reduce its harmful impacts.

"We have known of infestations around Coolah, Merrygoen and east of Coonabarabran for some time, but in the last two years there has been a marked increase with wort spreading through farms, lifestyle blocks and bushland," Mr Batten said.

"St John's Wort is actively flowing, so now is a good time for land managers to identify and control wort on their properties. St John's Wort will quickly takeover pastures and natural areas, particularly in hilly and inaccessible areas and once it takes hold it is very difficult to control," he said.

Castlereagh Macquarie County Council Senior Biosecurity Officer Andrea Fletcher-Dawson, is aware of the harmful impacts St John's Wort can pose to the environment and livestock.

"St John's Wort is predominately poisonous to livestock, particularly younger aged stock. Pale faced stock are the most at risk of impact after exposure to St John's Wort. It contains a chemical called hypericin, which causes photosensitivity, which when ingested, can cause large pink scabs to form across the face and body," Ms Fletcher-Dawson said.

"Other symptoms present in livestock include weight loss, still births and in worst case scenarios, death. St John's Wort is often identified through its bright yellow flower which if held towards the sun, pin size holes are present through its petals. However it is worth noting that plants that are less than a year old, will not flower, so you may have young plants present that are hard to spot," she said. 

St John's Wort is poisonous to pale- faced stock. The invasive weed can cause weight loss, still- births and in worst case scenarios, death.

Ms Fletcher-Dawson said there is huge concern surrounding the fast spread of St John's Wort. The invasive weed could impact not just the Warrumbungle region. 

"St John's Wort detections have more than doubled this year already. It is spread easily by its sticky seeds that can cling onto machinery, livestock or pest animals. It can also be spread by water or wind movement. Just one plant can produce up the 33,000 seeds, that can pass through the digestive system and remain viable for up to 12 years," Ms Fletcher- Dawson said.

"It is prominent and quickly spreading across the Warrumbungle Shire region, specifically around Coolah, Merrygoen and east of Coonabarabran. It has spread along the Oxley Highway from Coonabarabran to Gilgandra. There are no known detections of St John's Wort in Coonamble, Walgett or Warren shire regions," she said.

Although detections of St John's Wort are increasing, there are approaches the public can take to minimise the spread of this obnoxious wort.

"St John's Wort has spread so quickly this year to all different areas. It is important land holders and members of the public try to keep a look out, maintain your own property as best you can, and always check your vehicles before passing through other shires and neighbouring paddocks," Ms Fletcher- Dawson said.

"Chemicals are your best bet at reducing the spread of St John's Wort. You must identify and control the wort as quickly as possible. Even though some areas are not practical to get to at the moment, start to do something around the bordering line of a neighbouring paddock or try spraying the edges to keep the invasive weed out," she said.

Ms Fletcher- Dawson has a message for all land owners across the central west who are concerned about St John's Wort.

"My message is to keep onto it as best you can. Ring your local weeds officer for advice on appropriate chemicals to use. Always pick up the phone if you are unsure- your local weeds officer can come out to your property to inspect and identify the weed. Even though some land owners properties' have not been exposed to the wort as of yet, it is important to be aware of its presence and identify it as soon as possible to reduce its harmful impacts," she said.

General Manager of Castlereagh Macquarie County Council Michael Urquhart wants to remind landholders of their duty towards the Biosecurity Act 2015.

"Once land owners identify Wort, it is important that you control is quickly to prevent seed set. Unfortunately, physical removal is ineffective as new plants will grow from root fragments, in fact Wort can be spread through cultivation," Mr Urquhart said.

"it is imperative that all landholders remember their duties under the Biosecurity Act 2015. All plants are regulated with a general biosecurity duty to prevent, minimise or eliminate any biosecurity risk they may pose," he said.