Global Plant Protection News

From: IPM in the South

http://ipmsouth.com/2014/04/25/weve-made-progress-in-fighting-invasives-but-still-have-a-way-to-go/

We’ve made progress in fighting invasives but still have a way to go

Posted on April 25, 2014 by rhallberg

In the US alone, introduced species cause an economic impact of $157 billion, according to an article published in a 2005 issue of Frontiers in Ecological Environment. At that time, most of the attention for exotic invaders was being given to those that negatively affected crops. However, in the last 10 years, research and extension activities have expanded to include areas of public recreation and environmental concern (such as the hemlock woolly adelgid). Three authors from Tennessee and California explore “Introduced species policy, management, and future research needs” by looking at the status of introduced species management in 2005 and recommending ways that research could help. This post will add thoughts on ways that invasive species management has changed since then and how research has helped to inform the public about the importance of managing invasive species and how people can help.
The categories defining the most pressing issues in invasive species policy management have not changed much between 2005 and today. The greatest problems and needs for research and extension still include ways to keep unwanted species from crossing our borders and ways to effectively management them once they get in. Those who have to fight quickly spreading pests such as the hemlock woolly adelgid or kudzu have to deal with consistently shrinking budgets and a lack of manpower. However, some progress has been achieved in several areas:

Battling against invaders
Introductions usually happen in one of two ways: deliberately or accidentally. Although accidental introductions can be more difficult to track, deliberate introductions, such as hunters who move wild hogs to different states for gaming purposes, can be harder to catch initially. Other times, invasive species are sold at garden centers because of their public popularity, such as the mimosa tree or English ivy.
The authors recommend policy changes to better assess risk before a species is introduced. Basic facts about an organism, such as feeding habits, presence of local predators, conducive habitats and reproductive frequency could help inform those considering transporting a species from outside the U.S. to inside the border and then perpetuating its spread.
Accidental introductions are more difficult to prevent, and even with tougher legislation introduced in the 1990s, invasive species that hide in cargo or in shipping materials still pass through checkpoints unnoticed. Lionfish, for instance, has become a menace in the Caribbean and threatens the fishing industry, were introduced either through a damaged restaurant aquarium or by a pet owner unaware of the consequences. The redbay ambrosia beetle was probably harbored in a shipping container, and the hemlock woolly adelgid hitched a ride on an Asian hemlock purchased by a Virginia plant collector.

Finding invasives quickly and eradicating them before they take hold
Eradication involves erasing the presence of an unwanted species from a specified area. For instance, cotton growers might want to eradicate the stink bug so it would no longer be present in the U.S.. Completely ridding the country of a pest that populates many states is extremely difficult and often impossible. According to the authors, successful eradication is much more likely in species for which the distribution is limited. Even for these species, action must be taken swiftly for eradication to occur. One example of a successful widespread eradication effort is the Boll Weevil Eradication program, which has taken over a century to finally produce results in five states. Success of the program is no doubt due to the combined funding from federal, state and private sources. Most eradication efforts, however, suffer dramatically as funding dries up. For instance, an early attempt to eradicate the gypsy moth in Massachusetts failed after the state legislature withdrew funding for the effort after moth populations began to decline. Now, despite other state education efforts, the gypsy moth has spread to the Southeast.

Maintenance management at low levels
For most pest species, low-level maintenance—rather than eradication—is the goal. In fact, in crop situations, growers use action thresholds to determine the proper population level at which to begin control measures. For the most part, low-level maintenance is a more reasonable expectation than eradication. For pest species that feed beneficial species, low-level maintenance ensures the continuation of predators that may feed on a variety of pest species. Various species of lady beetles, for instance, may feed on aphids, scale insects, mildew, whiteflies, mealybugs and mites.

Invasive pest species are often best managed by using a combination of IPM techniques, including mechanical and cultural methods, chemical control and biological control. According to the article, mechanical and cultural control are often the most effective but are also the most costly and labor intensive. Chemical control used to be the cheapest and most immediately effective; however, recently several species of insects and weeds have become resistant to multiple pesticides. Herbicide-resistant Palmer amaranth is probably the most notorious of these species, and growers now are resorting to mechanical methods as well as chemical methods to control this weed.
The authors state that biological control is often ineffective; however, in the last several years, screening methods have tightened, and some biocontrol efforts are literally eating away at some of the most pervasive species. For instance, leaf beetles obtained from various countries in Asia are defoliating vast populations of Tamarix, or saltcedar, in Texas, Arizona and Utah. Scientists in the southeast are using several ladybug beetles to reduce the spread of this pest, and other researchers are looking into cross-breeding possibilities with compatible hemlock species that are resistant to the pest.

Although invasive pests that impact cropland still (and probably will always) receive greater attention than those that do not, education and outreach efforts for the public are beginning to raise awareness for some of the most damaging pests. Many in the general public now recognize terms such as emerald ash borer, hemlock woolly adelgid, Asian longhorned beetle and white-nose syndrome of bats. Some groups trying to manage invasives are even asking for citizen science help in locating invasive species so that populations can be more effectively tracked. Perhaps, with a combination of efforts, introduced species will eventually be quashed before they become “invasive.”

Source: Simberloff, D., Parker, I.M., and Windle, P.N. (2005) Introduced species policy, management, and future research needs. Front Ecol Environ. 3(1): 12-20.

NOTE: If you live in the Northeast in a state affected by Asian longhorned beetle and would like to be part of the solution to manage this pest, the USDA Animal and Plant Health Inspection Service (APHIS) is asking the public to report trees infested with Asian longhorned beetle so the agency can more accurately track the pest. Read the USDA’s blog for more information.
You can even help your kids learn more about invasives and about getting involved in citizen science projects. See the USDA Blog to learn about Insects Invade.