How the tree injector works
The aim of chemical injection is to utilise the tree's natural transport system to distribute pesticides, fungicides and fertilisers to the areas where they are most effective — without releasing any of these chemicals into the environment.
The Chemjet® Tree Injector is a spring-loaded device with a 20mm tapered nozzle that assists placement into the tree. Like a syringe, the chemical is drawn into the chamber in measured quantities up to 20ml. The injector is then locked off by turning the handle clockwise. Pair it with our 30%-strength injectable phosphite fungicide for the most effective treatment.
The injectors are placed in the tree by drilling a 4mm (wood-dependent) hole 50mm deep, and the tapered nozzle secures the injector firmly in place. Turning the handle anti-clockwise releases the plunger and injects the desired amount of chemical.
The tree takes up carbon dioxide and energy from the sun through the leaves, where it photosynthesises its food. The food (sugars and carbohydrates) dissolves in the sap and is carried downwards through the inner bark to every living cell — including the root system.
Tapping into the tree's natural circulatory process allows chemicals to dissipate rapidly and effectively, minimising wastage and maximising efficiency. The chemical reaches every element of the tree including the fine root hairs.
Applying chemicals by spraying is inefficient, especially against root pathogens, and a tiny fraction of conventionally used chemical is injected directly into the tree — without any release into the environment.
Other tree injection systems use high pressures, which can lead to cell damage around the injection site, impair sap flow and uplift the bark. The Chemjet® Injection system is the only low-pressure system available.
To determine the correct quantity and concentration of chemical, follow manufacturers' guidelines.
Prevention is better than cure
Items needed
- Eye protection and gloves
- High-speed drill (cordless preferable)
- 4.5mm (11/64") normal steel-shank drill bit
- Your chosen injectable product — most growers use potassium phosphonate
- Mixing container
- Container to carry loaded injectors (a bucket)
- All-purpose disinfectant — always spray your drill bit between trees, and any other tools you use
New to tree injection? Our starter kit for a single tree contains everything you need in one box — perfect for first-time use.
How to use
- Prepare the solution according to the manufacturer's label.
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Determine the number of injectors needed:
- Oak Wilt: one injector every 75mm (3") around the trunk
- Sudden Oak Death (SOD): every 125mm (5") around the trunk
- Phytophthora: every 200mm (8") around the trunk
- Drill 4.5mm (11/64") holes in the trunk between bark crevices, 40mm (1.5") deep, at a 45° downward angle.
- Draw the solution into the syringe and lock the plunger by turning ¼ turn.
- Push the injector nozzle firmly into the drill hole and twist clockwise. Don't over-twist — you could damage the tip.
- Hold the injector body down with one hand, twist the plunger handle ¼ turn to unlock, and tap the end to ensure it's activated. You should hear a click.
Work your way around the tree, repeating steps 4–6 and disinfecting the drill bit and injector tip as you go.
The injectors feed liquid into the tree's sapwood at a low 23 lbs pressure.
- Oak Wilt: normal uptake within 3–5 hours
- SOD: uptake is relatively fast — 5 to 45 minutes
Injection sites heal themselves. If you'd prefer, use beeswax to seal the hole.
Note: When injecting into trees with deep bark furrows (such as oaks), remove some outer bark with a chisel or drill to get a good seal — aim to inject into the furrows. Use a larger drill to reach the xylem layer if the bark is very thick, pushing the injector onto the external threaded portion.
Injector maintenance
When the injectors are empty, twist the syringes anti-clockwise and pull them from the trees into your container.
- Oak Wilt: wash with plain hot water (50°C+) and let stand 5–10 minutes. Drain and dry. The pathogen is heat-sensitive and 35°C destroys it.
- SOD and other applications: rinse in hot water with disinfectant. Put the injector tip in the solution and pull up and down a number of times. Always repeat this when changing products. Allow the injectors to dry.
Spray a silicone lubricant or WD40 down the barrel from the plunger handle. You can also put the tip in the lubricant and draw it into the barrel once or twice before expelling.
The injectors are now ready to be used again. Worn or leaking? Grab a pack of spare seals — they take a minute to fit and add years of life.
How to inject small-diameter trees
1. Use the spray tube from a WD40 can to make a 2mm outer-diameter injection tube. Follow the method in the pictures.
2. Fill the injector and fit the tube into the end.
3. Drill a 2mm hole as deep as possible (20–50mm) at working height. Push the slant-cut tube end firmly into the tree.
4. Use string to support the Chemjet — hang it with a loose loop. Unlock the plunger; liquid will drip-feed into the sap flow. Fluid uptake is slower through the smaller orifice.
Injecting small chestnuts for ink disease
Apply the solution as an injection at 0.77 grams active ingredient per cm stem diameter, at 4–5 cm above the soil. This equates to 16.5 ml of phosphite (diluted 5.5:1) per cm of stem diameter. For more on chestnut ink disease and other field research, see our Phytophthora research archive.