Birds spread the seeds by eating berries and then depositing them under shade trees. The plants are increasingly prolific in rainforest areas and along riverbanks.
Phil Kemsley, the district veterinarian with Lismore Land Services, said infestations of cestrum nocturnum were an emerging problem in the northern rivers.
“They have certainly spread particularly in the last few years with wet conditions and in some places it’s such a thicket, you can hardly walk through it,” Kemsley said.
“This most recent case would be the second I’ve seen in horses, but I have seen it in sheep and goats and cattle and suspected in a deer as well.”
Kemsley said it was probably also killing wallabies and other wildlife.
A department spokesperson said most reports of cestrum poisoning for livestock in NSW related to green cestrum or cestrum parqui, which is already banned from sale in most of the state. Cestrum parqui is a close relative that is a more entrenched weed including in the Hawkesbury-Nepean basin and the Riverina.
‘This is a plant that’s so closely related to a banned species. So why are we still selling it?’
Kemsley’s job is to investigate livestock deaths in the Lismore area, and he worked closely with Ludvik’s vet and attended the property.
Kemsley said autopsies of horses were dangerous because of the disease risk. They instead took a blood test from the surviving horse to check for liver enzymes, and found the toxicity profile matched both types of cestrum.
Kemsley then inspected the property and found it infested with cestrum nocturnum and obvious signs the plants had been eaten.
The third horse is expected to survive, either because it is bigger or because it ate less of the toxic plants.
Kemsley said the two types of cestrum look similar, but he was trained to tell the difference. When in fruit, cestrum nocturnum has large, white berries and the cestrum parqui has small, black ones.
Kemsley said wet weather could be a trigger for livestock eating cestrum rather than grass.
Ludvik said she had been clearing her property of weeds almost non-stop since the floods last year. She was focusing on the weeds she knew to be toxic, but this one was not on her radar.
For Ludvik the most galling thing is that cestrum nocturnum is still widely sold and planted.
“There are many poisonous plants but they’re not all this weedy,” she said.
“This is a plant that’s so closely related to a banned species. So why are we still selling it? Why are we promoting it? Why are we making more of a noxious toxic weed?”
The department did not answer questions about whether the sale of cestrum nocturnum should be outlawed.