International trade results in billions of tons of goods transported. Moving large volumes of anything invites unwanted hitchhikers including “invasive species”. Invasive species are species that are not native to a new location. They arrive from somewhere else. Invasive species populations greatly expand, displacing native species and can cause economic and environmental damage. Invasive species encompass plants and microbes as well as animals.
The US has a long history of importing invasive species. Both the house cricket and the Hessian fly (a pest of wheat) are invasive species that were transported to North America before the United States was formed as a country. The increase in world trade has accelerated the pace of importation of invasive species.
Important recent insect pest introductions include the Emerald Ash Borer that threatens all ash trees in the US and the Asian Longhorn Beetle, a pest of hardwoods. Most recently, the East Coast of the US is reporting large populations of the invasive stinkbug, Halyomorpha halys. Stinkbugs, as the name implies, smell bad and leave a foul odor on your hands if you disturb them.
What to do about invasive insects? The first line of defense is a set of inspections and regulations for goods leaving port to reduce the numbers of hitchhikers. Wood boring insects, for example, can be killed by treating the wood used in packaging of trade goods. Exporters of plants can be required to inspect their goods before they leave port. Goods face another round of inspection when they arrive at US ports. However, the volume of imports is so large than only a small percentage can be inspected.
Once pests are imported into the US, attempts are made to eradicate the pest. If that fails, a longer series of efforts aimed at controlling the spread and minimizing the damage may be implemented.
For management purposes, it is important to know where these species are located. The US gets this information through cooperative efforts between the States and the USDA. The States survey for invasive species and report the information to a Federal database.
One database, National Agricultural Pest Information System (NAPIS) maintains a website Pest Tracker. Pest Tracker provides up to date information on the results of state surveys and a series of maps showing sites where the pest has been reported.
In addition to survey data, Pest Tracker has links to information on control and management efforts. Pest Tracker is a good resource for scientists, journalists and homeowners who need more information on what is bugging them.
Emearald Ash Borers damage Ash by tunneling under the bark.
How fast does it take for invasive species to spread? How are they able to adapt to the conditions and the environments here so quickly in order to reproduce before dying?
Invasive insects often take many years to spread. Gypsy moth was introduced into the US in the 1860s. It has only recently spread to NE Indiana and is not yet in much of southern Indiana. Emerald Ash Borer has been in North America since the late 1990s, but it was only found in Tippecanoe County this year. Soybean aphid was first noted in the early 2000s and it has spread everywhere east of the Rockies in less than a decade. How fast the species spreads depends on its biology and the climate.
Have other animals been introduced to maintain the current pests? For example, is there an animal that will eat a gypsy moth? If so, could this be part of a possible solution to control the gypsy moth population, or are the risks of the unknown side effects of the animal too great?
Geneticists are trying to breed an American white ash that is resistant to the EAB, similar to an Asian ash species. Is the same procedure being done for other tree species?
Many tree species are bred for many types of resistance, but it can be slow because of the lengthy time (several years) required for many trees to reproduce.
There have been biological control agents for invasive species. There is a virus that controls gypsy moth and also a fungus.
Biocontrol agents must be investigated before they are imported. An example of bad results is the mongoose introduction into Hawaii.