Early actions needed in weed management

Natural Resources Adelaide & Mount Lofty Ranges district officer David Hughes spoke at the recent Angaston Hogget Competition forum and said the wet season had contributed to a boost in weed growth.

“This year people are bringing weeds to the office that we haven’t seen in 10 or 15 years,” he said.

Mr Hughes said the most concerning weeds were caltrop, silverleaf nightshade, heliotrope and, in the coming months, Cape tulip, which could all have a negative impact on livestock health.

He said these were weeds that were generally poor competitors against thick pastures, but would germinate quickly on bare ground.

“This year caltrop is a big issue and has really thrived,” he said. “A lot of people don’t realise caltrop can be quite poisonous.”

Caltrop can germinate quickly and reach seed set within 14 days, so it can quickly become a larger problem, he warned.

“The idea is not to allow it to set seed, which can be hard because it has such a short cycle,” he said.

Mr Hughes also warned that the notifiable weed silverleaf nightshade could also be spreading into new areas.

“It is not cheap to treat and will take away the production of a property very quickly,” he said. “Using the right chemical can also stop setting seed but you need to get the timing right.”

Heliotrope was another weed that had high incidence.

Mr Hughes said proper quarantine of properties was one of the first steps to avoiding weeds spreading into new areas.

“It is very easy to get a new infestation,” he said.

Seeds can be spread through pets, native wildlife, along waterways, or new livestock from different areas.

Human interaction was also a major factor, such as buying in hay or secondhand machinery that may carry seeds. Other vehicles on the property could also be an issue.

“Quarantine of the whole property is important,” he said.

Mr Hughes said research showed silverleaf nightshade seeds could stay in a sheep’s digestive system for up to 21 days.

“If you get new stock, put them in a holding paddock and monitor weeds in that paddock,” he said.

He said it was also important to monitor new stock near existing outbreaks.

He said stock that had previously been exposed to certain weeds were less likely to be affected.

“If a plant is new to the property and livestock have not seen it before, it can be bad,” he said. “And if you’re bringing in new livestock from different districts, you can get a few deaths.”

Mr Hughes said unfamiliar weeds could be taken, wrapped in plastic bags or ziplock bags, to Natural Resources offices for identification.

“If there is something you don’t want on your property, and you’ve got a few plants, jump on them and make sure they don’t seed,” he said.