Exotic-Pest Primer

Exotic Invasive Pests in Southern California Gardens

The following is a sampling of exotic, invasive pests found in Southern California gardens:

Ash Whitefly

  • Attacks fruit and shade trees
  • First found in California in the late 1980s
  • Caused defoliation, fruit loss, and tree death
  • Brought under control by a parasitic wasp from its native Middle East and Mediterranean

Black Scale

  • Periodic citrus pest and consistent issue for olives in San Jacinto Valley
  • Likely native to Africa, arrived in California before 1880
  • Infests a wide range of plants
  • Controlled to some extent by a natural enemy introduced in 1940, but still a persistent problem
  • Decreases fruit size and production when infestations are high

Eucalyptus Longhorned Borer

  • Discovered in Orange County in 1984
  • Destroys eucalyptus trees in larval stage by cutting off nutrient supply
  • Removal of dead trees costs $500–$5,000
  • Controlled via education, resistant species research, and parasite introduction

Formosan Subterranean Termite

  • Native to mainland China, introduced from Hawaii over 10 years ago
  • Colonies can exceed 1 million termites
  • Highly destructive—can render homes uninhabitable within two years
  • Strong presence in San Diego
  • Limited control success with insect growth regulators

Giant Whitefly

  • Likely native to Mexico
  • Attacks over 50 common ornamental plants
  • Causes defoliation, stunting, and potential plant death
  • Found in California, Texas, Louisiana, and Florida
  • Miniature parasitic wasps show promise in early field trials

Mediterranean Fruit Fly (Medfly)

  • First discovered in Southern California in 1975; reappeared in 1998
  • Affects at least 253 species of fruits, nuts, and vegetables
  • Females lay eggs under fruit skin; maggots rot the fruit
  • Researchers are studying behavior in Mediterranean regions for control strategies

Red Gum Lerp Psyllid

  • Australian native first detected in South El Monte in 1998
  • Rapidly spread across California, damaging eucalyptus trees
  • Feeds on plant fluids and can kill trees if untreated
  • Six Australian parasites being studied for natural control
  • Best prevention: proper watering, avoiding over-fertilizing and overpruning

Red Imported Fire Ant

  • Native to South America; major issue in the southern U.S.
  • Stings cause painful pustules, potential scarring, and in rare cases, death
  • Detected in Orange County in 1998
  • More than $1.1 billion spent annually in Texas on control efforts
  • Researchers studying insect behavior and insecticide options

Julie Bawden-Davis

Julie Bawden-Davis is a bestselling journalist, novelist, blogger, and YouTuber. A prolific author, Julie writes in several genres. She enjoys creating page-turning suspense served up with a dose of romance, garden books that turn any brown thumb green, and spiritual books meant to enlighten and inspire. Widely published, Julie has written 45 books and more than 4,000 articles for a wide variety of national and international publications. She lives in Southern California, where she enjoys sunny, blue skies most days and year-round gardening. Julie gains inspiration from being surrounded by plants when she writes.