More and more landscape contractors are adding tree care to their services. If you are thinking of offering this service, the best way to begin ? with no investment in eauipment, sprayers, etc. ? is by using the micro/macro injection or infusion method.

Landscape professionals are increasingly being asked by homeowners and condominium/apartment managers to maintain and manage their trees? health. Insect and disease problems often occur suddenly, and frequently represent a crisis that demands immediate attention. In response, these professionals usually contact tree health control specialists to deal with the problem with an appropriate spray.

But, why can?t landscape professionals control tree health care problems? One answer may be that application of sprays to shade trees in urban areas requires specialized, expensive equipment.

Microinjection, however, is a technique that allows the introduction of materials, such as antibiotics, fungicides, insecticides and mineral nutrients, directly into a tree without any contact with the environment. Microinjection does not require investment in new equipment, since most people already have battery-powered drills. Microinjection has become an increasingly popular clinical alternative to spray applications in the control of health problems of urban trees.

What is microinjection and how does it work?
Microinjection is a type of trunk injection where small amounts (approximately 0.1 ounce) of therapeutic chemicals, contained in sealed capsules, are introduced into shallow trunk wounds around the base of a tree. The injected chemicals are then distributed systemically by sap movement within the tree to the branches, leaves and even roots, within a few hours after injection.

Although the first reports of trunk injection of trees date to studies by Leonardo DaVinci in the Middle Ages, it is a technology that is often misunderstood. Materials in liquids can be injected into the woody tissues, known as xylem, of trees because the pressure within the xylem is below that of atmospheric pressure on the outside of the tree. Under this condition of negative pressure, liquids introduced into healthy xylem through a fresh injection wound will be taken into the xylem and distributed within the tree in the sap stream.

There is no need for the use of high pressures to attempt to ?force? liquids into the tree. High pressure injection often damages tree tissues and does not place the injected materials into the outer xylem where most systemic transport occurs. Low pressures sufficient to empty the injection reservoir are most effective for transport and cause the least impact on the tree.

Trunk injection of several gallons of materials per tree, or macroinjection, has been used primarily to treat trees with vascular diseases, such as Dutch elm disease. Unfortunately, most tree species do not have the xylem porosity of the American elm and cannot accept large volumes of liquids via trunk injection. In addition, macroinjection systems involve complex tubing and reservoir systems which are very labor intensive, and are not practical for rapid treatment of numerous trees.

A breakthrough in injection technology occurred in the 1960s when the systemic insecticide Bidrin, in microinjection capsules, was injected into trees and shown to control a variety of chewing and sucking insect pests. It was then clear that large volumes of materials were not needed to be injected into a tree to control a tree health problem. Research on Bidrin demonstrated that a small volume of a concentrated systemic chemical in a microinjection capsule could provide effective tree health care.

Since that time, the focus of microinjection research has been on developing systemic formulations of antibiotics, insecticides, and fungicides that were effective in low volumes. Considerable research has gone into studies of the most effective injection techniques to maximize uptake and distribution, and to minimize any possibility of wounding the tree. Recently, combinations of an insecticide and a fungicide in a single capsule have been developed to allow microinjection treatment of both insect and disease problems with a single injection.

Today, microinjection is both an evolving, research-based technology and a clinical tool for the tree health care practitioner. Research on microinjection is continuing on the potential systemic uses for new chemicals, which are being produced and registered each year to promote tree health care. However, for this microinjection technology to be used effectively and not cause harm to the tree, the clinical applicator must receive training in its correct use. One-day short courses on the proper application of microinjection therapy for trees are presented in most areas of the United States during the winter conference season.

Tree health care is an area of expanding need and opportunity for the landscape professional. The use of sprays to control tree health problems is being met with increasing public opposition. Microinjection is a contained delivery system that presents the applicator with an environmentally-friendly alternative to spray applications. A further advantage to adding microinjection to the services you provide is the low initial investment required to perform this service.

Editor?s Note: Terry A. Tattar, Ph.D., is Professor and Director, Shade Tree Laboratory, Department of Microbiology, University of Massachusetts, Amherst. Dr. Tattar has conducted extensive research on vascular transport and vascular diseases of trees and often presents seminars on microinjection technology. He can be reached by phone at 413-545-2402 and by email at

October 2001