View From The West: Aliens Continue To Invade the West

View From The West: Aliens Continue To Invade the West

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Critical issue: Turn your eyes westward, read the papers, watch the news, and you will continue to hear about the ongoing invasion in which unwanted aliens come ashore and enter California and other western states. The border is not secure.

This issue involves growers, regulators, inspectors, policy makers, and the general public. No, we are not referring to labor issues or extra-terrestrials but rather the onslaught brought about by invading insects, pathogens, mollusks, weeds, and other pests. Certainly not unique to western states, this alien invasion by a host of organisms threatens agriculture and other ecosystems and is a sobering reminder of similar issues shared elsewhere in the U.S.

The Aliens

The list of documented immigrants is extensive and varied, and new names of unwanted guests are regularly added to the lineup. Insects top the list because so many of these arthropods hitch rides and are carried into new regions. California has a long history of seeking, finding, and eradicating the Mediterranean fruit fly. Asian longhorned beetles threaten hardwoods in California, brown marmorated stink bugs have invaded numerous regions and are moving westward, and the Asian citrus psyllid has already arrived and can contribute to the downfall of the citrus industry due to the pathogenic bacterium that it vectors. The light brown apple moth is causing great concern to growers of fruits and vegetables in California.

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New, invasive plant pathogens will cause concern for many agriculturalists. Previously, California unfortunately made the national and even international news with the outbreak of sudden oak death disease that affected dozens of forest and nursery plant species. While this damaging fungus is no longer considered a “new” invader, it continues to be an important quarantine and regulatory issue. The fungus causing thousand cankers disease has been detected out here on walnuts. Tomato yellow leaf curl virus has been detected on California tomato, though it appears to not yet be established here.

Pathogens also take down animals, with poultry dying from the fatal virus that causes exotic Newcastle disease. This spring, horses in California have died from the very contagious and deadly equine herpes virus-1. Many invasive weeds are also on the list of documented immigrants, with giant reed being one of many examples.

The aquatic world is not immune from the alien invasion, as the west has experienced the introduction of pests such as the European green crab and Quagga and zebra mussels. The invading crab is an aggressive, successful colonizer of diverse marine habitats, resulting in disruption to the natural ecosystem balance and reduction in populations of endemic marine species that are harvested commercially. The two mussel species alter the marine food web, change the habitat, and can actually result in fish die off. The mussels also heavily colonize, clog, and damage water intakes, pipelines, screens, and pump mechanisms at power and water treatment facilities.

Impact And Strategy

Invasive alien pests are disruptive. Farmers, ranchers, nurserymen, forest managers, and others have their hands full managing endemic pests and diseases and trying to maximize production or maintain the ecological health of the existing system. When these new problems arrive, further stress is placed on the agricultural and ecological systems. Production costs increase, yields can decline, plants and animals die, and ecosystem balance can be lost.

The defensive strategy or the standard operating procedure regarding invading agents remains well established:

– Maintain vigilant detection programs that search for these introduced pests.
– Implement quarantines and other regulatory measures to check incoming materials for the pests.
– Use available IPM practices and
resources to control the pests.
– Conduct research that will increase understanding of invasive pests and develop additional detection and control tools.

The Role Of The Economy

The current economic downturn could have a negative effect on our management of invasive pests and pathogens. Decimated state and federal budgets may mean the elimination or reduction of certain programs. Under-staffed and under-funded programs will make invasive pest detection that much more difficult. Also, dwindling university research budgets may result in fewer researchers and Extension agents who are available and able to study these invaders. Information is power, and if new information is slower in being developed, we could experience difficulties in the fight against invading aliens.

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