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BUGS AND BUGABOOS: Beware the Trojan Plant

Gifted plants may contain more than meets the eye. Image credit: Starkus01

By Vincent Lazaneo.

You may admire certain plants growing at a friend’s home, but you should be wary about accepting one if offered. The botanical gift and any soil transported with it could be a Trojan plant harboring hidden pathogenic fungi, bacteria, or viruses; parasitic nematodes; pest insects; or weed seeds that are not currently in your garden. Keep in mind that a harmful organism, once introduced into your garden, may be difficult or impossible to get rid of.

Buying plants from a reputable nursery can minimize, but not entirely eliminate, the risk of acquiring a new plant pest or disease. The use of clean soil media and sanitary cultural practices can enable wholesale nurseries to produce plants free of harmful pathogens and pests. The system works well most of the time but problems occasionally occur. Retail nurseries may at times receive defective plants from a wholesale source and plants that are clean may be compromised before they are sold. Responsible nursery personnel are the first line of defense, followed by regulatory agencies including county, state, and federal departments of agriculture.

The retail customer is the final line of defense. If you notice plants at a nursery that may have a disease or pest, you should inform the nursery manager. If you are not satisfied with the response, you can report the problem to the County Department of Agriculture, Weights and Measures. An inspector will follow up by visually inspecting the plants and collecting samples for lab identification if needed. In San Diego County, residents can also submit a sample of a diseased plant or an unknown insect from their property for free identification by a plant pathologist.

Adult Asian Citrus Psyllid. Image source: USDA ARS Image Gallery

Citrus HLB Update

On the topic of unwanted pest invasions, there was a dramatic increase last year in the number of citrus trees in California with the lethal bacterial disease Huanglongbing (HLB), also known as citrus greening. We are now in the exponential growth phase of the disease and the number of citrus trees with HLB will continue to accelerate.

When I wrote about HLB in April 2017 (Deadly Citrus Disease Nearby, pg. 12), a total of thirty-four citrus trees with the disease in California had been confirmed by the California Department of Food and Agriculture. As of January 25, 2018, there were 347 citrus confirmed with HLB in the state according to Steve Lyle, Director of Public Affairs with CDFA. The total had climbed to 382 on February 2 when I contacted San Diego County Plant Pathologist Pat Nolan. And by March 13, the total was 495. Most of the diseased trees were detected in Los Angeles County. Some were also detected in Orange and Riverside counties. HLB has not yet been detected in San Diego County.

What can you do about HLB at home? Learn to recognize the symptoms of HLB, know how to check your citrus for Asian Citrus Psyllid (Diaphorina citri), and learn what to do if the insect is present. See the UC IPM Pest Note “Asian Citrus Psyllid and Huanglongbing Disease” and if you suspect a citrus tree has HLB, call the CDFA exotic pest hotline at 1-800-491-1899 to have the tree checked.

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