Tree Injections

What are Micro Injections
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.

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 most of 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.

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 became clear that large volumes of injected materials were not needed to control a tree health problem. Research on Bidrin demonstrated that a small volume of a concentrated systemic chemicals in a microinjection capsule could provide effective tree health care.

Since that time, microinjection research has focused on developing systemic formulations of antibiotics, insecticides, and fungicides that are effective in low volumes. Considerable research has gone into studies of the most effective injection techniques of maximizing uptake and distribution, and minimizing any effects of wounding. 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.

Today, microinjection is an evolving, clinical tool for the tree health care practitioner. Research on microinjection is continuing in the direction of potential systemic uses for new tree health care chemicals which are being produced and registered each year.

Treatment of Lerp Psyllids

There is a widespread misconception that the lemon gum eucalyptus is a thin-barked tree. When this tree’s outermost bark is scarified or scratched, a band of green tissue, resembling the deeper cambial layer of other species is exposed. This phenomenon is common to numerous trees, including the london plane, chinese elm and many tropical trees.

This green tissue layer is actually composed of living cells that contain chlorophyll, enabling the tree trunk to produce energy via photosynthesis. Indeed, rather than being an indication of “thin bark,” it can be an important factor in tree defense, providing energy for the vital process of compartmentalization etc.

It is apparent that lemon gum eucalyptus bark may actually be much thicker than commonly believed. In fact, in various areas of a single tree, the bark may actually vary from 1/2 “to 3/4″deep.

Some eucalyptus bark is known to be sensitive to various environmental stimuli. Particular care should be taken in performing microinjection, or any procedure that may intrude into the bark. Bark sensitivity is the probable cause of this species’ susceptibility to frost, heat (from flame), etc. Similarly, chemical spray, and even animal urine are known to affect tree bark (P. P. Pirone, Tree Maintenance). Following frost or other environmental stimuli, dimpling frequently occurs along the trunk. Generally, eucalyptus trees recover well from these events, including micro-injection.

The” bleeding” ooze observed at such sites is called “kino”. The following article by L.R. Costello, provides additional information, on what kino is and what function it serves in assuring tree health/ vitality. For further explanation of kino, see A. Shigo, Tram,.
Over the past few years, several species of Lerp psyllid have been introduced into the United States. One is the red gum Lerp psyllid (Glycaspis brimblecombei, whose primary host is the red gum eucalyptus tree (E.camaldulensis). This infestation has spread throughout much of the state and has already destroyed thousands of trees.

The most recent arrivals are the spotted gum lerp psyllid (Eucalyptolymamaidenhi) and a free flying pest, the brown psyllid (Cryptoneossa triangula). These two insects have been spreading rapidly and are of great concern to growers. They attack lemon gum (E. citriadora) and spotted gum (E. maculata) eucalyptus trees. Psyllids are small insects that suck sap from leaves and like the eucalyptus tree itself, are native to Australia.

Heavily attacked eucalyptus which endure multiple defoliations, exude copious honeydew prior to dying. The resulting blackened foliage is due to a sooty mold which forms, clinging to the honeydew. Psyllids form their lerps, secretionary structures produced by psyllid nymphs as a protective cover.

The term “lerp” is derived from an aboriginal word meaning “house.” In California to date, the red gum lerp psyllid has been recorded on the following species: Eucalyptus camaldulensis, E. rostrata, E. rudis, E. globulus, E. deiversicolor, E. sideroxylon, and the list keeps expanding. Infestations have been observed in most California counties and wherever susceptible species of eucalyptus are grown.

There are 127 species of lerp psyllids occurring throughout Australia and beyond the Philippines. Most species are associated with Eucalyptus spp. But there are a dozen others associated with Melaleuca spp. These lerps (resembling scales), differ greatly from most species of psyllids, even those in the same genus.

History of Lerp Psyllids

Yesterday it was an Australian problem. Today it’s a California problem. Tomorrow it will be a problem in Arizona, Nevada, New Mexico, Texas.. . which of the Southwestern or Southeastern states will become the next victim of this minuscule insect that has diligently, meticulously, and almost methodically devastated literally thousands of beautiful Eucalyptus Red Gum trees that have offered shade to Californians ever since the Spaniards imported them from Australia many years ago?

The Eucalyptus was originally planted by the Spaniards to be used for railroad ties because they are so resistant to many decay organisms. Then the Spaniards discovered Redwood trees and abandoned their idea to use the Eucalyptus trees. Because California’s climate is so similar to Australia’s, they have spread quite freely and are now referred to as “escaped cultivation.”

Until two years ago, this native Australian’s chief enemy was the longhorn beetle. However, in June of 1998, trees along the freeway in El Monte, in Los Angeles County, were found heavily infested with an unknown insect. Samples were taken and the insect was identified as the lerp psyllid (Glycaspis brimblecombei). It also turned out to be a North American record; this was the first of its kind to make its way from Australia to California. Within months, the lerp psyllid’s presence was reported in many other counties throughout California.

Used as ornamentals, Red Gum trees provide sun protection for homes; they are used on golf courses and in parks. Because they make great shade trees, they are also popular as street trees. In only two years, tens of thousands, if not hundreds of thousands of these trees, from San Diego to San Francisco, have been devastated by the lerp psyllid. The eggs hatch; the nymph psyllid puts its ovipositor into the leaf, then it starts spinning, forming a lerp, which is an Aborigines word for house. It’s the consensus that a tree will put out new growth an average of three times before it dies from lack of stored up energy.

Don Smith, western regional products manager for Simplot Partners, says “The lerp is nothing more than the solidified honeydew from the feeding of the insect that actually hardens into this small igloo over the top of the psyllid that protects the nymph; that little igloo is called a lerp.”

Adult psyllids are light green or yellow in color, three millimeters long, and move by hopping about, or flying. They do most of their damage as nymphs, in their immature stage, and as adults can reproduce at an alarming rate.

Because this was a new infestation to North America, there was no known chemical to combat this insect. Some academicians began to look at using predators for control, but they are having trouble with gestation. The Psyllaphagus wasp, collected in Australia, appears to be a specific parasite to the lerp psyllid. Recently, 200 wasps were released in an area; however, its too early to tell the results. In addition, control may take several years.

In the meantime, the J.J. Mauget Company has been working with their product containing the chemical imidacloprid, which was developed by the Bayer Company under the brand name of Merit. J.J. Mauget Company’s trade name for its product is Imicide and uses the microinjection method for control.

Imicide is injected into the tree, going through the tree’s vascular system, and out to its leaves. It begins working immediately; if the leaves are still viable at the time of injection, it protects those leaves. If the leaves are not viable, the new growth that comes out is protected. Once the insect begins to feed, it is killed. It’s a systemic material, killing the insect in the nymph stage.

Buster Litton of Country Green had several clients whose trees had serious insect infestation. He came across imicide and tested the product. The results have been star startling Litton reports 100% success with the product. “In one particular town I injected a group of trees; I went back a month later and there was new growth coming in. Now, a year later they are still receiving protection.”

Kevin Corcoran of KC Horticulture Services has treated hundreds of trees. The trees that we treated look like trees; the untreated trees are totally defoliated. These trees are all pushing out new growth that is coming out beautifully clean.

Since the homeowner cannot purchase and apply this chemical, application is best handled by a professional. The average cost to the homeowner is $50-$60 per tree, including labor. The important thing to understand is that we must be alert and aware of the severe damage that this insect can do. And, it won’t be long before this California problem becomes a Nevada problem, or a Texas problem. In fact, Arizona, Louisiana, and Arkansas – all the Southwest and Southeastern states are vulnerable to attack from this vicious little lerp.


I read your article in the RSF Review today, and I wanted to add a little personal experience to the lerp psyllid control issue.

I live two canyons away from RSF and I’m not in the Covenant, but I share the concern about this problem because my little acre-and-a-half is covered with approximately 1,000 eucalyptus trees, most of which are red gums. About two years ago when the infestation first hit us, my trees were completely covered with lerps within a matter of weeks. It was horrible as you know.

I hit the Internet and researched all I could, and way back then I read an Internet article by Dr. Dahlsten, which strongly suggested that other than his wasp program, nothing would work to control these pests, including pesticides. Not believing everything I hear, I kept researching. I landed on a Web page by a pesticide company. It contains fairly well-documented studies and arguments that injected pesticides will work to effectively control red gum lerp psyllids,’ and immediately I had to question Dr. Dahlsten’s comments. After talking to the Mauget people at great length, I opted to spend the money and inject each and every one of my trees. This was two years ago…

Today I have 1,000 healthy trees on my property, and all of my neighbors have sick and dead trees, or they have cut their trees down. After the injections were completed, it was only a matter of three to four weeks before there were no live lerp psyllids to be found on my property. The trees began to refoliate immediately, and my property started looking very good in a very short time.

The story has changed from “it won’t work” to “because the holes necessary to inject the trees can cause infection” etc. now that’s all well and good, but here it is two years later – I have zero infections, very healthy trees, and a beautiful forest.

I was told by Mauget that the injections would only last nine to 10 months and I’d have to do hover again every year. The reality is that two years later, there are finally a few lerps coming back, but not in any great quantity. Mostly they are on trees that I missed or were too small to inject.

The bottom line: for the amount of wealth in RSF, I find it hard to believe that money could be in the way of cleaning up your trees, and injections do work and they work well, so why don’t you get the word out in a positive way, get the program rolling and save the trees?

Gary Stadler

Rancho Santa Fe