Moth plant

Moth plant has naturalised and is now well-established in the neighbouring Auckland and Bay of Plenty regions and common in parts of the Waikato region; it is established in Hamilton and many northern parts of the region including parts of the Coromandel.

Moth plant grows from a short taproot (main root) and other weak shallow roots. It prefers loose, fertile soils in warmer, wet areas. The self-fertile vines are spread mainly by their wind-borne seeds. When the pods dry out, they split open and release large numbers of seeds attached to silky threads. The seeds can germinate in high light and semi-shade and establish long distances from any seed source. Moth plant vines can smother and kill desirable plants and prevent regeneration in coastal environments, on cliffs, in shrubland and along forest tracks and margins and in urban areas.

A recent study notes that the intolerance of moth plant to cold restricts the southern expansion of this pest plant in New Zealand, and the shallow root system is a limitation in dry soils.

While moth plant only occurs in certain parts of the Taupō and Rotorua districts within the Waikato region, the impact of this pest may be significant in these areas.

Taupō and Rotorua district (within the Waikato region):

Waikato Regional Council is responsible for controlling moth plant in the Taupō and Rotorua Districts (within the Waikato region) and it is illegal for anyone else to remove or disturb it there.

If you see moth plant on your property in this part of the region, do not cut, treat or try to remove it. Call 0800 800 401 to report it to your local biosecurity pest plant officer.

Waikato region (outside of the Rotorua and Taupō districts):

Physical control (all year)

• Best results are achieved between December and February before any pods are produced.
• Pull out seedlings. Hoe or dig out mature plants, removing as many roots as possible.
• Leave any detached vines in the host tree/hedge to wither and die.
• Remove all seed pods and take them to a refuse transfer station to prevent further spread. Do not burn the pods, compost them or leave them lying around, as seeds might spread.
• Revisit the site after three to five days when missed plants will be obvious. Dig out any remaining vines.

Herbicide control (summer to autumn)

Remove all seed pods from the vine(s) before applying herbicide. As above, do not burn or compost the removed pods or leave them lying around. Take them to a refuse transfer station instead.

Cut vine treatment (for smaller infestations)

Cut stems 20cm above the ground, then coat the stem and hanging ends liberallywith herbicide. Herbicide must be applied immediately after the cut is made. Some herbicides are available in a bottle or gel form, making application easy and convenient.To purchase the herbicide, visit your local hardware, rural supply store or garden centre.

Spray application (for larger infestations)

Spray the plant and totally cover leaf surfaces with herbicide. Apply the herbicide carefully to avoid serious damage to other plants you want to keep. Apply during the active growing season (spring to autumn) for best results.

Safety when using herbicides

• Follow the instructions on the manufacturer’s label.
• Always wear protective clothing.
• Always minimise the risk to your other plants.
• Contact the supplier for further advice.

Summary of herbicides and application methods for control

Management

After initial control, it’s important to:

• clean out the site again at least annually to control regrowth
• in pastures, apply fertiliser then over-sow with a clover/grass mix
• lift the fertility of the site, which may help prevent seedling growth.