Why is it a pest plant?
Woolly nightshade is a problem because it can form dense stands that crowd out other plants and stop them from growing. It invades pastoral land, native forest margins, scrublands and urban areas. A single plant can produce many thousands of seeds, which are spread by birds. These seeds can lie dormant in the soil and germinate up to 20-30 years later.
The berries of woolly nightshade are moderately toxic to people (especially children) and they may be poisonous to livestock. The leaves shed fine hairs when touched, which irritate the skin, eyes, nose andthroat, and in some cases cause trouble with breathing.
Woolly nightshade is well established in many areas north of Taupō. It thrives throughout the northern parts of the Waikato region, with dense stands occurring in the Port Waikato area and on the Coromandel.
Responsibility for control
All landowners/occupiers in the Waikato are responsible for the control of wooly nightshade on their property.
All landowners/occupiers are responsible for controlling woolly nightshade on their properties and are required to work with Waikato Regional Council in areas where control programmes are in place. Woolly nightshade is also banned from being sold, propagated, distributed or included in commercial displays.
How to control woolly nightshade
Small plants (less than 60cm) can be pulled out and left to dry after shaking all dirt from the roots. Larger plants that are cut down need to have the stump treated with herbicide or they will regrow. Try not to disturb the soil.
Cut stump treatment
Cut the tree down, leaving a stump no higher than 5cm above ground level. Immediately (within two minutes of cutting) paint herbicide over the entire stump surface, including the sides.
Drill and inject
Drill 10mm holes around the trunk at a 45 degree angle, 50mm deep and 50mm apart. Fill each hole with herbicide.
To control larger trees, make shallow downward cuts around the trunk below the lowest branch and near the ground using a machete or axe. Cuts should overlap to effectively ringbark the tree. Apply herbicide liberally to each cut.
Basal treatment of trunk
Using a specific basal treatment herbicide* liberally paint or spray the trunk from the ground to a height of 30cm to 50cm, making sure to cover the entire trunk. *Talk to your local herbicide retailer for more information.
Totally cover the leaf surfaces with herbicide. This method is most suitable for smaller plants, but pulling out plants by hand may be cheaper and easier.
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
|Glyphosate||Drill and inject, stump swabbing, stem frilling (Note: Glyphosate is NOT suitable for overall spraying).|
|Amitrole||Drill and inject, stump swabbing, stem frilling, spray application.|
|Triclopyr||Stump swabbing, drill and inject, stem frilling, trunk base treatment.|
|Picloram gel||DStump swabbing.|
|Triclopyr/picloram mix||Drill and inject, stump swabbing, stem frilling, spray application.|
|Herbicide rules will apply. You may need to notify neighbours if spraying. The Waikato Regional Plan explains the agrichemical (herbicides) use rule in section 6.2.|
|If applying herbicide over water, a resource consent may be required. Please check with Waikato Regional Council before you begin.|
After initial control, it’s important to:
- clean out the site again at least annually to control regrowth
- stop weeds invading by replanting with non-pest plants (preferably native plants) once regrowth is no longer a problem.
- For advice and additional information on control methods, call our pest plant staff on freephone 0800 BIOSEC (0800 246 732).
- Chemical company representatives, farm supply stores and garden centres can also be good sources for advice.
View, download or order the following publications or call our freephone 0800 800 401.
- National Pest Plant Accord (Manual of plants banned from sale, propagation and distribution) ($10.00 plus GST)
- Plant Me Instead! (Plants to use in place of common pest plants) (free)
- Waikato Regional Pest Management Plan (RPMP) (free) (Section 5.3, page 46)
- Waikato Regional Council pest guide (free)