Imported insect species are invasive, hard to control

Kudzu bug, also known as globular stink bug, is an imported pest that has few natural predators and feeds on kudzu, soybeans and other plants.

Tony Bertauski

Many things have changed since ships began making voyages with goods and services, and not always for the better.

Introduced species of insects become invasive because few predators and parasites feed on them. As a result, their populations soar and they can decimate plants. Here are a few of the more bothersome transplants that can be found in the Lowcountry:

The gypsy moth was introduced in 1868 to boost the silk industry when native silkworms became susceptible to disease.

Gypsy moths escaped from the lab and became one of the most destructive pests of hardwood trees in the Northeast.

Their populations were so high that sidewalks would be covered with caterpillars in the morning, making the trip to the car a slimy one. Aggressive monitoring and control methods have helped slow the spread.

The Japanese beetle was introduced in 1916 at a nursery in New Jersey, thought to have arrived with iris bulbs from Japan. Not a very troublesome pest in its native country, it has become a serious pest on flowers, leaves and fruit on more than 200 species of plants.

It can be found in the Lowcountry feeding on roses, crape myrtles and other things. Milky spore disease has been used to control the pest, but results vary. Pheromone bags can attract the adult by the bagful, but work best if placed far away from plants they prefer.

Asian ambrosia beetle entered the United States through Charleston in 1974. The small beetle, about the size of a grain of rice, bores into twigs of a variety of trees and shrubs, introducing the spores of the ambrosia fungus that it carries on its body. The beetle feeds on the fungus, not the wood, as it infects the host and eventually will kill the branch.

While many hosts tolerate the damage, an ambrosia beetle specific to redbay trees, introduced into Georgia in 2002, is wiping out redbay trees, native to the Southeast, throughout the Lowcountry.

The small tree will all at once wilt and die. Options for chemical control are being developed, but redbays should be cut down and burned once symptoms are apparent.

Red imported fire ants, introduced from South America in the 1930s, likely came in soil used as ship ballast. Imported fire ants are much more aggressive than native fire ants, spreading throughout the Southeast and displacing much of the native species. Parasites, diseases and predators have been identified in South America and introduced in the United States. For example, phorid flies hover over mounds and divebomb ants when they emerge and lay eggs in their heads. When the flies hatch, the ants' heads pop off. While this won't eradicate imported fire ants, it is aimed at reducing the aggressive activity.

Recently, the kudzu bug has become a problem. It feeds on the invasive vine, kudzu, which was introduced from Japan in the late 19th century as fodder and erosion control and has since overrun the South. Killing kudzu is good. However, the bug also feeds on other plants, such as soybeans, and that's a problem.

The kudzu bug was discovered near Atlanta in 2009 and invaded South Carolina. They are exceptionally tough to kill. They are related to stink bugs, emitting caustic secretions as a defense mechanism. Crushing one will fiercely offend your nose.

In some areas, kudzu bugs have been reported to invade houses during the winter. In this case, vacuuming the insects is a better option than stepping on them.

Tony Bertauski is a horticulture instructor at Trident Technical College. To give feedback, e-mail him at tony.bertauski@tridenttech.edu.