Pest shrubs and trees don’t just get in the way – they can take over natural ecosystems like forests, wetlands, coastlines, and farmland. Their rapid growth can:

• Block out sunlight
• Alter soil conditions
• Outcompete native plants.

Controlling them takes more than just chopping them down as most will regrow unless treated properly. The best approach depends on how persistent the species are and how widespread the infestation is.

Here’s how to tackle them for good by choosing the right control method!

Non herbicide control

Hand pulling

• Works best on small seedlings or shallow-rooted plants.
• Minimise social disturbance – exposed soil invites new weeds to grow.

Ring barking (good for pine trees)Ring barking

Not suitable for species like sycamore, which can regrow from the base or heal the wound in their bark.

1. Use a chisel, axe, or saw to make two deep (into the sapwood) cuts around the base of the trunk, at least 5cm apart.
2. Remove all bark between the cuts to disrupt nutrient flow.

Herbicide control options

Cut & paint (great for shrubs and resprouting trees)

This is an easy and often best technique to use with shrubs, smaller trees and species that are likely to re-sprout from the base e.g elder or Darwin’s barberry.Darwin’s barberry cut

1. Cut the trunk close to the ground with a straight flat cut. The cut must be flat so the herbicide will sit on the cut area and not run-off.
2. Apply herbicide to the cut surface within 30 seconds. This ensures the herbicide is taken up by the plant before the sap stops flowing.

Use a squeeze bottle or paintbrush – just enough to wet the surface, avoiding excess run-off. Herbicide gel is easy to use, mess-free and can be purchased from most garden supply or home improvement stores.

Spraying (for plants under 1 metre tall)

Use a knapsack sprayer or spray gun for full coverage. Avoid using this on large woody plants.

To avoid harming nearby desirable or native plants, reduce spray drift by:

• Avoiding windy days—gusts can carry herbicide off target.
• Spraying in the early morning or late afternoon—warm midday air rises, increasing drift.
• Adjusting spray output—opt for a controlled stream over a fine mist to keep herbicide particles in your target area.
• Avoiding spraying in wet conditions—rain can wash herbicide into non-target areas or sensitive environments.
• Shielding native plants—using a half-bucket or barrier keeps them safe from accidental exposure.

Other top tips for successful spraying:

• Time it right – spraying during peak growth (before flowering or fruiting) ensures plants absorb the most effective dose.
• Use the correct herbicide – double-check you’ve got the right product for the specific weed you’re targeting.
• Follow the label – mix and apply herbicide as directed. Never dip used containers into water sources and always use water-safe sprays near streams or ponds.
• Boost effectiveness – add a sticking agent (surfactant) to help herbicide stay on leaves, consider marker dye to track where you’ve sprayed, or use a foaming agent to minimise drift.

Drill (or slash) & inject (best for large trees)

This is ideal for hard-to-remove species like crack willow, especially where felling might harm nearby plants. You can use a sheep drench pack and gun, or a plastic squeeze bottle with a long nozzle.

How to do it:

1. Drill downward holes or use a chisel to make deep cuts into the sapwood at even intervals around the base of the tree.
2. Apply herbicide immediately into each cut or hole (check the product label for correct dose).

Don’t ring-bark the tree as that will reduce herbicide absorption.
Note: Dead trees will remain standing. Check for any safety risks in public or high-use areas.

Wilding pines and conifers: getting to grip with identifying and controlling

Wilding pines and conifers are a significant biosecurity issue in New Zealand from the mountains to the sea. Like many weed species they are well adapted to New Zealand conditions and out compete many slower growing native species.

When established as pure wilding forests they destroy our unique biodiversity and landscapes as well as iconic landscapes and cultural heritage. They can also impact on water volumes in rivers and adversely affect productive land.

Knowing how to identify wilding pines and conifers and which species they are helps with determining the best way to control them as some species are harder to control than others.

Get in behind and help our national campaign to remove wildings. You can be active on the ground removing trees and/or explain the problem to your community and get more people onboard.

For more information go to: Control Guidelines now available - Wilding Pine Network NZ and Wilding conifer quick guide - Wilding Pine Network NZ.

If you are contractor or landowner who wishes to do work at scale control techniques and good practice guides are available on National Control Programme | Wilding Pines