By Miriam Raftery
August 20, 2012 (San Diego’s East County) – Asian Citrus Psyllids, tiny insects that can carry a disease capable of wiping out California’s citrus industry, have been found in several East County communities as well as North County and other southern California locations.
A quarantine is in effect across most of our region.
Prompt identification of infested trees in backyards and commercial groves is crucial, since treatment can kill the bugs. But once a citrus tree becomes infected with citrus greening (also known as Huanglongbing [HLB] or yellow dragon disease), there is no cure. Fruit becomes inedible and the tree ultimately dies.
“Mostly south of I-8 is where the main problem lies for San Diego County, and down into Tijuana,” Tracy Ellis, PhD, Agricultural Scientist, Entomology with the County of San Diego told ECM today. Hot spots for infestations include Dulzura, Tecata, Potrero, Crest and Alpine; an infestation was also found in El Cajon.
In North County, psyllids have also been found in Valley Center and Bonsall. “Unfortunately it’s getting into the main growing areas,” Ellis said.
Scope of the threat
To date, only one case of HLB disease has been found in Southern California—in Los Angeles, where it was identified in March. But the disease has wiped out over 40% of Florida’s citrus crop, devastating millions of acres of citrus across the U.S. and abroad including Asia, Africa, the Arabian peninsula and Brazil. It was first reported in Asia in the 1800s.
“All agencies including the United States Department of Agriculture, U.S. Department of Homeland Security, California Department of Agriculture, and the County Agricultural Commissioners are doing their best to prevent the spread of this vector pest,” Ellis told ECM.
To date, San Diego and Imperial Counties have been actively setting out sticky traps to locate the pests and have succeeded in keeping the disease from taking hold and limiting the Asian citrus psyllids spread.
Los Angeles, however, has been less fortunate. “They have given up the fight of treating the residences in Los Angeles,” said Ellis, citing “overwhelming numbers—almost 10,000 find sites in L.A. So they decided to make a barrier going eastward to try to protect Ventura and Riverside Counties.” But she added, “It’s making a march eastward tdo Riverside very quickly.”
How to identify the Asian citrus psyllid
The insect is small-about the size of an aphid. The mother psyllid lays eggs only on new growth. If you see a curled leaf, unroll it and look inside. While several pests can cause leaf curl, here are tips for identifying Asian citrus psyllids.
“People can look on new growth of citrus tree for any little critters with red eyes-that’s a giveaway, plus they have tubular wax secretions, a spiraling wax tube,” Ellis explained. “The mother rests at a 45-degree angle to the leaf.” A mother psyllid can jump like a grasshopper. She will also lay tiny eggs that hatch many small nymphs.
How to spot Huanglongbing (HLB) or citrus greening disease
The disease itself causes symptoms that may mimic other diseases, such as yellowed or malformed leaves. The key distinction is that HLB causes yellowing that is assymetrical, or uneven, on the main vein. By contrast, discoloration due to nutrient deficiencies is symmetrical, or even on both sides.
While psyllid insects can be killed with the insecticide, if a tree actually becomes infected with HLB disease, the only option is to remove the tree in order to prevent spread of the disease to other citrus trees.
The disease does not harm humans. However, the California Department of Agriculture has warned that it poses a serious threat to the future of California's citrus industry if not swiftly controlled.
Who to call for help
If you suspect that your citrus tree(s) may have Asian citrus psyllids or HLB disease, call 800-200-2337.
Treatment of infestation
Early treatment is critical to save your trees.
“There are insecticides that are very effective against the Asian citrus psyllid,” Ellis assured. The California Department of Food and Agriculture (CDFA) will pay for treatment of trees at residences, with permission of homeowners. (Commercial growers are responsible for treatment of their groves.)
Treatment includes a contact insecticide applied to leaves, as well as watering an insecticide into soil at the base of the tree. The insecticides typically used are pyrethroids derived from chrysanthemums and neonicotinoids derived from nicotine. The later has been altered to remove portions harmful to humans.
There is a quarantine in effect, so do not transport citrus fruits grown in your backyard or elsewhere in our region to other states or counties, since they may harbor psyllids or citrus greening disease.
If you purchase a citrus tree or seedling, be sure the grower can assure that it is free of the disease and Asian citrus psyllids.
If have dead or dying citrus trees that you can no longer care for, County agriculture officials recommend that you consider cutting them down, since abandoned trees may harbor the insect or the disease. The County Commissioner is looking into whether the County can abate abandoned trees; there is precedent in that CDFA has cut down abandoned trees in the past with the property owner’s permission.
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If you suspect your citrus trees are affected in San Diego County, call 800-200-2337.