Local Land Services target St John's Wort

24th January 2023

Local Land Services is urging farmers to be on the lookout for St John’s wort (Hypericum perforatum) with current conditions across north west NSW ripe for the weed.

St John’s wort contains the toxin hypericin, which causes photosensitisation in sheep, cattle, horses and goats. The skin damage associated with this problem leads to weight loss, reduced productivity and, in extreme cases, death.

Local Land Services Regional Weed Coordinator Jo Skewes said now was a critical time for control with the weed capable of growing in a variety of areas including well established competing pastures, riparian areas and bushland.

“One St John’s wort plant can produce 30,000 seeds annually, so early identification and control is paramount,” Ms Skewes said. “The sticky seeds are spread primarily by animals and may remain viable in the ground for more than 20 years, so it is important that all known infestation sites are regularly monitored. All new plants must be treated before seed set, as every plant left untreated has the potential to produce thousands of new plants.”

North West Regional Weed Committee Chair Ian Schwartz encouraged landholders to take action now.

“St John’s Wort is a priority species under the North West Regional Strategic Weed Management Plan,” Mr Schwartz said. “The best way to control St John’s Wort is to take an integrated control approach. An effective spray program to be undertaken now, followed by pasture seeding and fertilising to help establish desirable pasture species to help out compete new St John’s Wort seedlings.”

Infestations can also be grazed heavily in winter to help control the weed.

“Biocontrol agents are present in some areas but to date have not been an effective tool to get large infestations under control,” he said.

There is a general biosecurity duty for any person who deals with a plant that poses a risk of causing an adverse effect on the economy, the environment or the community and who knows, or ought to know about the risk the plant poses, has a legally enforceable duty to prevent, eliminate or minimise the risk of that impact occurring.

To get more information on St John’s Wort check out the WeedWise app (www.dpi.nsw.gov.au/weeds) or download the North West Regional Strategic Weeds Management Plan (www.lls.nsw.gov.au).

For technical advice and assistance with identification please contact your local council weeds officer.