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The Bagrada bug: A new pest in San Diego County

By Vincent Lazaneo

bagrada bug
Photo by: G. Arakelian

Name: 
Bagrada bug, Bagrada hilaris.  Other common names include painted bug and harlequin bug, which is also the common name of a related species (Murgantia histrionic).  The bagrada bug is a member of the stink bug family Pentatomidae and it emits a distinctive pungent parsley odor when disturbed.

Distribution
The bagrada bug is known from Africa, southern Asia, and southern Europe.  It was first found in North America in June 2008 in Los Angeles County, California.  It has since spread throughout southern California, Arizona, and New Mexico.

Hosts
The bagrada bug feeds on a variety of plants in the family Brassicaceae (Cruciferae) including many important food crops:  arugula, broccoli, cabbage, cauliflower, Chinese greens, kale, kohlrabi, mustard, radish, rutabaga, and turnip.  It also attacks papaya, potato, corn, sorghum, cotton, capers, wheat, millet, canola, some legumes and other crops.  It also feeds on an ornamental alyssum and some weeds:  wild mustard, London rocket, pepperweed, field bindweed, purple nut sedge, lambs quarters, and perennial sow thistle. 

Damage
Bagrada bug adults and nymphs have needle-like mouth parts and they remove sap from plants.  It is not known to bite humans or carry disease.  The insects’ puncture marks appear as white patches on edges of leaves and larger stippled areas.  Young plants that are heavily attacked have a wilted or scorched appearance and may not produce a head or produce multiple small heads. 

Identification and Life Cycle
Bagrada bug adults are about 1/5 inch long (5-7 mm) and have black shield-shaped bodies with distinctive white and orange markings.  Females, which are larger than males, can lay up to 100 eggs in a 2-3 week period under host plants and on plant foliage.  Eggs are oval to barrel-shaped, creamy white when first deposited and turn orange with age.  Nymphs emerge in 4-8 days.  They are wingless and pass through 5 instars (developmental stages) as they shed their skin and grow.  First instar nymphs have a reddish brown head and thorax and a bright red abdomen.  Later instars become darker adding black color to their bodies and develop wing pads.  All life stages are usually present together on host plants and adults are commonly observed mating.   In southern California there are multiple generations each year and populations usually peak late in summer and fall.

Bagrada bugs adults and larger nymphs are sometimes mistaken for lady beetles because they are similar in size and bright coloration.  The bagrada bug also resembles the harlequin bug (Murgantia histrionic) although this insect is somewhat larger (7.5-11.5 mm).  The adult bagrada bug’s body is more black than orange color and the inverted “face” on its back is a diagnostic characteristic. Photos of the bagrada bug can be seen at http://cisr.ucr.edu.  

Biological Control
The bagrada bug is not native to California and there are no natural enemies here that specifically attack it.  Spiders and other general predators feed on bagrada bug; however birds apparently find its taste unpleasant and may avoid eating it.  Bagrada bug populations can rapidly increase and biological control alone may not keep its population in check. 

Management Options
Bagrada bug adults, eggs and nymphs in soil are difficult to control.  Solarizing soil during warm weather prior to planting will control adults and nymphs and may also control eggs if the soil temperature is high enough.  Covering prepared and well-irrigated soil for a period of 4 to 8 weeks during warm sunny weather will help control some soil-borne diseases, weed seeds, nematodes, and insect pests.  For more information see UC Pest Note 74145 Soil Solarization for Gardens and Landscapes at http://www.ipm.ucdavis.edu.

Host plants can be protected from the bagrada bug if soil is free of the pest by covering areas planted with seed or transplants with floating row cover fabric.  Sunlight and air pass through the spun-bonded fabric but insects are excluded.  A wide selection of row cover fabrics are sold online through garden catalogs.

In small gardens hand picking may help control the bagrada bug if few insects are present on host plants.  Application of insecticides is usually needed to protect young plants from severe damage when bagrada bug populations rapidly increase.  Before any insecticide is used, carefully read the product label to make sure it can be used on the plants you wish to treat. 

Some insecticide products labeled for use in home gardens may be effective against the bagrada bug.  The insecticide pyrethrin controls certain insects on contact and it breaks down quickly, usually within a day.  Insecticidal soap and horticultural oils, including neem oil and paraffinic oil, kill soft-bodied insects on contact and do not have a persistent toxic residue.  These materials would be more effective against nymphs than adult bagrada bugs.  Other insecticides like Spinosad (an organic product) and carbaryl (Sevin) have a more persistent toxic residue which may harm honey bees and other beneficial insects.

By V. Lazaneo, UC Urban Horticulture Advisor, Emeritus

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