Citrus disease threatens California trees File - In this undated file photo, the Asian citrus psyllid is seen in this University of Florid...

Citrus disease threatens California trees

File - In this undated file photo, the Asian citrus psyllid is seen in this University of Florida photo provided by the University of California, Davis. The California Department of Food and Agriculture announced Friday that citrus greening, also known as huanglongbing, has been discovered in lemon/pummelo tree in a residential neighborhood of Los Angeles County. The bacterial disease is carried by the Asian citrus psyllid and attacks the vascular system of trees. (AP Photo/University of Florida, Michael Rogers, file)

File - In this Jan. 24, 2012 file photo, citrus entomologist Mamoudou Setamou, holds an orange that is showing signs of citrus greening disease in a grove in San Juan, Texas. The California Department of Food and Agriculture announced Friday that citrus greening, also known as huanglongbing, has been discovered in lemon/pummelo tree in a residential neighborhood of Los Angeles County. The bacterial disease is carried by the Asian citrus psyllid and attacks the vascular system of trees. (AP Photo/The Monitor, Nathan Lambrecht, File)

File - In this Jan. 24, 2012 file photo, Mamoudou Setamou, center, a citrus entomologist for the Texas A&M University Kingsville Citrus Center in Weslaco, walks through the grove where citrus greening disease has been found in San Juan, Texas. The California Department of Food and Agriculture announced Friday that citrus greening, also known as huanglongbing, has been discovered in lemon/pummelo tree in a residential neighborhood of Los Angeles County. The bacterial disease is carried by the Asian citrus psyllid and attacks the vascular system of trees. (AP Photo/The Monitor, Nathan Lambrecht, File)

Plant pathologist Erik Mirkov holds an early citrus rootstock called C22 that is enhanced with the genes from spinach, Wednesday, March 28, 2012, in a lab at the Texas AgriLife Research and Extension Center in Weslaco, Texas. Testing has shown the genetically enhanced citrus trees are immune to citrus greening, a disease that has ravaged the industry. (AP Photo/Christopher Sherman)

California bug detectives are fanning across a Los Angeles suburb, setting traps and taking tissue samples from backyard citrus trees in a frantic effort to stop the spread of a tree-killing disease detected there last week.