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.
According to Arnold Farran of the J.J. Mauget Company, the adult psyllid lays its eggs on the leaves. Although they prefer new growth, they are found on all foliage. 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. The lerp is a protected structure where the nymph lives. It?s hard to get to with a spray chemical, and it?s protected from most predatory insects. The nymph sucks the juices from the leaf, which kills the leaf; the leaf falls off, while the insect grows and lays more eggs on more leaves.
Through its stored energy, the tree puts out new leaves and the insects begin to feed on them. It can only put out new growth a certain number of times, until all its reserved energy is used up. 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, it?s 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 imadcloprid, which was developed by the Bayer Company. Under the brand name of Merit, imadcloprid is used as a soil drench. 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 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."
On another project, he relates: "On this one street all the trees were infected. The guy at the bottom of the street sprayed his trees twice, which really is an ineffective treatment. His neighbor at the top of the street had me inject his trees. A couple of months went by; his trees looked great. The guy who sprayed his trees would walk by every day and see his neighbor?s trees looking great, while his trees were looking very bad. This year he called me; I went over and injected his trees. I also injected the guy at the top of the hill a second time, because he wanted to make sure his trees stayed healthy.
"After a month, the newly injected trees started leafing out. What makes this so dramatic is that the guy between the two did nothing to his trees. You can stand at the bottom of the street, look up, and see the difference in the one-year treated trees, the one-month treated trees, and the untreated trees. The guy at the top of the hill has trees that look like a million bucks," says Litton.
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. However, since the area is infiltrated with this bug, the new growth may get several lerps, but as they feed on the tree, they take the chemical into their system and die before they have time to lay eggs.
"There are a number of species of trees that this bug is infesting and Imicide works on all of them. It kills the longhorn borer and a number of other insects as well," explains Corcoran.
Mike McCauley of Mike?s Tree Service has been on the ground floor of testing Imicide. He?s on his third year of treatment with some trees. "If you hit them early in the season, it seems to work better." He suggests injection the first year with Imicide. Then, if the client has a lot of trees, the second year use Merit, a soil injection product by Bayer, as a ground treatment.
Imicide, as a tree injection treatment, puts imadcloprid directly into the tree and begins to work immediately. Merit, as a soil injection treatment, puts the active ingredient into the soil, and works as it is absorbed by the tree?s root system. Both, of course, work systemically.
"The really neat thing about the micro-injection procedure is that everything goes in the tree, nothing goes in the air," explains Litton. "In most cases it doesn?t kill the good bugs, it kills the bad bugs. I personally have treated several hundred trees and in every case have seen 100% improvement."
In July 1999, Dr. Lester Young, a professor of Agriculture Biology in the Department of Horticulture/ Plant & Soil Science at California Polytechnic University, Pomona, began clinical trials on forty trees with extremely heavy infestation. One year later, the injected trees are still showing no signs of infestation.
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.