By Sharon Cohoon, Sunset senior garden writer

Beautiful bug; big problem.

The shiny black insect nestled in the petals of a white rose, seen above, is rather gorgeous in a sinister sort of way.  But, unfortunately, Diaprepes abbreviatus, commonly known as the citrus root weevil, is a serious menace to the California citrus industry.  This Caribbean insect made its way to the U.S. in 1964 in an ornamental plant shipment from Puerto Rico to Florida.  It then made its way to Texas.  And in 2005 it showed up for the first time in Southern California. Since it has been sited in Huntington Beach, Costa Mesa, Yorba Linda, Long Beach, Carlsbad, Encinitas, Oceanside, Rancho Santa Fe, and elsewhere.

D. abbreviatus is a large, colorful weevil, 3/8 to 3/4 inch long, and can range in color from gray to yellow to orange and black.

The adults feed on leaves and leave semi-circular notches on the margins.  They may feed on fruit as well.  But it is the larvae stage of the insects that is the real threat.  When the grublike larvae fall off the leaves, they burrow into the soil and start feeding on the plant's roots.  They can kill a plant by girdling the root system in as little as 8 months.

In addition to citrus, D. abbreviatus feeds on avocado, guava, peaches, hibiscus, palms, Indian hawthorn, Brazilian pepper, and oaks.  In all it threatens about 270 plant species.  (Despite this picture, it does not appear to harm roses.)

If you find an insect you suspect might be the citrus root weevil, please notify the California Department of Food and Agriculture on their hotline.  800/491-1899.  The Deparment will inspect your plants and treat with insecticides if needed.

For more information on this pest, see the UC Davis publication 8131.