Getting Chemicals Into Trees Without Spraying Part 1: Implantation and Injection
Capsules containing the pesticide are implanted
in the sapwood into a pre-drilled hole, and the
chemical is absorbed by the tree.
Chemicals can be applied to trees to repel or kill damaging insects, to treat or prevent fungal diseases, to provide nutrients, and to kill sprouts, stumps, or even entire trees with herbicides. Spraying is the most typical way to apply these chemicals, but in some situations, sprays are inappropriate. Some chemicals can be placed or injected inside trees easily, which is what we’ll cover here. We’ll cover trunk implantation and trunk injection in this article and soil injection/drenching and trunk basal sprays in the next Utah Pests News issue.
These techniques work by placing water soluble chemicals just under the bark. The chemicals then move into and through the tree in the sap, and end up mainly in the leaves. Therefore they are good for treating leaf-feeding insects like aphids and adelgids. Borers and bark beetles can be killed if the chemical location and timing are just right, but this is often difficult to achieve.
Implantation – The main available implant is a capsule containing the chemical that is held in a gelatin shell. It is inserted into the tree in a hole drilled into the sapwood. Water in the sapwood dissolves the capsule and the chemical is taken up. Several are used per tree and they are placed low on the trunk in the root flare. Acecaps and Medicaps are the only implant brands currently available (treecareproducts.com and treerx.com). Implants are inexpensive, usable by non-experts, available through many retail nurseries, and easily installed. The main disadvantage is that the holes are fairly large (1/4-3/8 inches diameter).
Injection – In trunk injection, liquid chemicals are injected into the stem through various types of holes and devices. Some systems use holes drilled in the trunk and a system of tubing and barbed plastic fittings to drain liquid chemicals into the trunk by gravity from a container hung above. Medi-ject for treating iron chlorosis is one example, but it uses large drilled holes. Also lack of pressure can make uptake slow. Low pressure systems that can speed uptake include the Mauget system which uses plastic capsules that you pressurize by depressing a plunger and then insert into a drilled hole. Similar systems are Tree Tech Microinjection Systems, and Rainbow Treecare’s M3 Infuser. These systems require small, drilled holes (1/8” to 3/16 inches diameter), are fairly simple to use, and are slower than high pressure systems.
Injection system without pre-drilled holes.
Higher pressure systems inject chemicals using either a syringe or tubing, tees, and a chemical reservoir designed to be under pressure. These include Arborjet’s Tree I.V. system that uses tees, tubing, and a pressurized reservoir, and their Quik-Jet system that applies small chemical volumes with a syringe. Equipment costs for these systems can be high and they are fairly complex. Rainbow Treecare also has pressurized tubing and reservoir systems.
ArborSystems’ Wedgle injection system is unique in that it doesn’t use drilled holes but relies on injection with a syringe and a special needle. It is fairly fast because of the pressure created by the syringe. Equipment and methods for this system are fairly complex and equipment cost is high. No holes are drilled, but bubbles sometimes form under the bark which become wounds.
Pines and other resinous conifers produce resin when their living tissues are pierced and this resin can block chemical uptake. Special pressurizable tubes called STITs (Systemic Tree Injection Tubes) are used to overcome this. They have been used for treating Scotch pines for pine wood nematode. Commercial STITs are available from Rainbow Treecare and Mediject. ArborSystems has a different tip they use for injecting resinous conifers called the Portle that is said to reduce leakage and get more chemical into the tree.
Advantages of trunk injection methods include use of a low chemical volume, relatively simple equipment in some cases, it can be done in windy or rainy weather, and there is little non-target organism exposure. Disadvantages include the creation of wounds by drilling holes or by bubbles/embolisms, coverage can be spotty throughout the crown, and treating every year would be risky.
Use of trade names and specific product examples is not meant to imply endorsement of certain products. Always read pesticide labels and follow directions.
For a complete fact sheet on this topic go to Kuhn’s Forestry Website at forestry.usu.edu and click on fact sheet #20, or click here.
-By Dr. Michael Kuhns, Extension Forestry Specialist, Wildland Resources Department, Utah State University Cooperative Extension, Logan. Kuhns maintains a very informative website at forestry.usu.edu.