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Invasive Plants, Along For The Ride

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Imagine $122 billion dollars out of our pockets and our economy.  That is the annual amount of monetary damage from invasive species to the US.  Those species include insects and weeds.  The invaders have few barriers, a tremendous drive to populate our shores and eat up our crops.  Our best hope for control, and the least costly, is by preventing the introduction and establishment of these invasive species.

The historical pipeline for the invasive insects and weeds has been from countries that provide the US with goods.  In search of cheap goods many of the products come from Asia, and in turn, many invasive pests come along for the ride. No surprise that many of the pests are Asian. All these foreign pests arrive by trade or tourism.

Los Angeles International Airport is an arrival point for 61 million people coming in on international flights from 58 countries.  Most invasive pests arrive in cargo shipments.  In the past, the ships would take months to arrive causing the pests to starve to death.  Now shipping is much quicker with more stops at more ports allowing the pests to arrive in good shape.

Once the invasive pests land on our shores they are beyond their natural range and become pests in a new environment.  Having developed in a different ecosystem these non-natives have few, if any, natural enemies and quickly take advantage of the situation.  They soon overwhelm the native species using up all the natural resources.  The common traits of invasive pests are rapid reproduction, fast growth, wide dispersal, quick adaptation to new habitats and the ability to deal with a variety of weather conditions and food sources.

An example of an invasive pest that has wreaked havoc here at home is the Asian Citrus Psyllid.  Twenty years ago, the Asian Citrus Psyllid (ACP) landed near the port of Miami.  Hurricanes moved the ACP north spreading quickly and decimating the Florida citrus industry with the disease the ACP carries, Huanglonbing (HLB).  HLB can kill a citrus grove in 3 to 5 years.  In 2001 ACP spread to Texas then on to San Diego.  The California Citrus industry has spent millions to combat this invasive pest.

The San Joaquin Valley has temperatures that range in extremes compared to Southern California.  Thoughts were that freezing temperatures in the winter would kill or stop the forward movement of the ACP.  To be an invasive species they must be adaptable, and the ACP most certainly is.  Both the Federal and State Departments of Agriculture have spent thousands of man hours and millions of tax dollars in chasing and destroying ACPs and many others.  With traps, sprays, parasitic wasps, and controlling movement of plants and fruits, hopes are with a slowdown of the migration.

The job of a home owner in fighting HLB is one of diligent observation in finding and identifying.  Quarantines of the citrus plants and fruits help prevent the spreading of disease. We all must be detectives to stop the severity of this disease; it is a death sentence to hundreds of thousands of citrus trees.   The California Department of Agriculture has excellent information and pictures of both the pest and the disease.  See for pictures and reporting of sightings.

As with any hitchhiker there is danger.  The list is long for both the insects and weeds.  Become familiar with plants and insects especially when you are purchasing plants and produce from other areas. If it has something that is abnormal it is better to ask and report.  Protect yourself and your community from these invasive killer pests.

Julie Silva is a University of California Cooperative Extension Master Gardener of Tuolumne County.

UCCE Master Gardeners of Tuolumne and Calaveras Counties can answer home gardening questions. Call 209-533-5912 or go to: to fill out our easy-to-use problem questionnaire. Check out our website at: You can also find us on Facebook.