A few months ago it seemed that gypsy moths were going to be the big bug story of this summer. This long-established pest of eastern forests is moving into northeastern Illinois in significant numbers. Traps baited with gypsy moth pheromones and placed all over Cook and Lake counties are attracting large numbers of interested males. At Cook County’s Salt Creek Nursery forestry crews putting together new traps reported males flying into the building where they were working.
But gypsy moths are getting very little attention in the local media, having been pushed out of the spotlight by a new menace, the Asian long-horned beetle. This insect apparently entered Chicago in crates, packing materials, or pallets holding goods from China. Its native range extends from Japan and Korea south through China to northern Vietnam.
The Asian long-horned beetle, Anoplophora glabripennis, has been detected in trees in the Ravenswood area, and a lone individual has been found in Buffalo Grove. In Cook County the Forest Preserve District has advised its forestry crews, nature center employees, and volunteer stewards to be on the lookout for the beetle, but as yet none of the insects has been found in a forest preserve. A suspicious bug detained by the Willow Springs police last Friday turned out to be a common variety of native long-horned beetle–of which there are many.
As a rule of thumb, if you have trees, you probably have long-horned beetles. More than a thousand species are native to North America. The Illinois Natural History Survey has published a field guide to species in this state that displays hundreds of different kinds.
They all belong to a family called the Cerambycidae, members of which are most readily recognized by their extremely long antennae. The antennae of males are often longer than those of females, and in some species they are substantially longer than the bodies.
Long-horned beetles are all plant eaters, and the larvae specialize in eating wood. Some feed on the sapwood of living trees, others on the bark, others on the roots. Some specialize in newly dead wood; these can cause considerable damage to recently felled trees that have not yet been cut into lumber. Some specialize in wood in an advanced state of decay; they play a significant role in forest ecology as decomposers of wood and as food for larger animals. If you see a woodpecker banging away at a tree trunk, it may well be looking to uncover the larvae of a long-horned beetle.
Many long-horned beetles specialize in particular species of trees. There are locust borers and sugar maple borers and cottonwood borers and redheaded ash borers and painted hickory borers. There is the oak-twig pruner, which lives out at the ends of branches, where it chews through new twigs, and there is the tile-horned prionus, which feeds on the roots of various hardwoods.
Adult long-horned beetles have more varied eating habits than the larvae. Some do not feed at all. Others eat fungi, sap, fruit, or plant roots. Many are attracted to flowers for pollen and nectar. They are perhaps the most important pollinators among beetles. I have found that goldenrod flowers are a good place to look for long-horned beetle adults in late summer. Most of the beetles on the flowers are likely to be orange-and-black soldier beetles, but I have encountered yellow-and-black sugar maple borers as well. Beetles, like many other insects, have two pairs of wings, but in beetles one pair is modified into hard, shell-like coverings called the elytra. On soldier beetles, the elytra don’t quite cover the entire abdomen. Looking down at the insect, you can see a bit of gut extending beyond the ends of the elytra. In long-horned beetles, the elytra cover the entire abdomen.
The business end of a long-horned beetle, and especially a long-horned beetle larva, features two clawlike mandibles–mounted sideways, not vertically like our jaws–that chew up whatever the beetle is eating and deliver it to the mouth. Long-horned beetles can bite, and with mandibles capable of chewing through solid wood, they can bite pretty hard. If you should happen to find one, handle it with care.
We are only the second location in North America to be visited by an infestation of Asian long-horned beetles, but gypsy moths have been on this continent for about 130 years. In that time they have spread from New England to the south and now the midwest. As their name suggests, they do move around. The high-flying males can travel great distances. The nearly flightless females need help from the wind to move, but apparently they get that help often enough to allow them to spread over millions of square miles.
We have weapons to use against gypsy moths, principally a foliar spray and a bacterium called Bacillus thuringiensis, but both approaches have serious drawbacks. Foliar sprays of insecticide release large quantities of toxic substances into the environment. Bt, as the bacterium is usually called, works, but it works against all lepidoptera. In other words, it takes out hawk moths, luna moths, monarch butterflies, and anything else with scaly wings. Most damning is the fact that neither the insecticides nor the Bt has succeeded in doing anything more than damping down local outbreaks. Environmental groups have opposed the use of both of these weapons on the grounds that they do more harm than the moths.
What the caterpillars of the gypsy moth do is defoliate trees. If the infestation is heavy enough, they can produce a “December in June” effect, stripping all the leaves from large trees. A healthy tree can survive one or two such incidents, but if the infestation continues the tree dies. A tree under stress can take considerably less gypsy moth damage than a healthy tree, and many trees in our forests have been stressed by close crowding and heavy shading. Gypsy moths will go after almost any hardwood, but they are especially fond of oaks. Since various species of oaks are the most important trees in our local forests, the gypsy moths may turn out, long-term, to be far more damaging than the Asian long-horned beetles.
For the immediate future, the big question is whether we can successfully contain the beetle invasion. After all, we have cut millions of elm trees in eastern North America, yet Dutch elm disease is still very much with us. To get a sense of our chances, I talked with Bob Mungari, director of the division of plant industry at the New York State Department of Agriculture and Marketing. New York, specifically Brooklyn and Amityville, is the location of the only other outbreak of the Asian long-horned beetle in North America. The beetles were discovered there in August 1996. Since then the effort to control them has required the removal of about 2,000 trees. In the east, where sugar maples are a dominant tree in the forests, a new pest that favors maples is a real nightmare.
According to Mungari, the program is showing signs of success. The sedentary habits of this species may help us control it. The beetles have slightly expanded their range, but the growth is one tree at a time rather than by leapfrogging to more distant areas. Cutting will continue for a few more years, and monitoring will have to go on for many years after that. But Mungari is confident that the outbreak can be controlled. The program also involves a quarantine on any wood moving out of the affected area. “What we have to do,” he told me, “is suppress these outbreaks until we can come up with a more effective control.”
After the New York outbreak the U.S. Department of Agriculture budgeted $500,000 for research on controlling the beetle. Investigators from the department are working here and in China, searching for biological controls or other means to deal with this troublesome insect.
In the meantime, we might think about the general question of GATT and nature. We have decided that widespread contact and trade are good for us. I agree with that decision in a general way, though I have major objections to NAFTA and other initiatives of free-trade ideologues. But long-horned beetles, zebra mussels, kudzu, buckthorn, and a host of other exotic species might be telling us that we need some precautions. A global economy may enrich us, but it could impoverish the nest of nature.