Jan. 23 2019 10:48 AM

The invasive pest reached the Bay Area in 2016 — now it’s within the city limits.

Asian citrus psyllid
David Hall, USDA Agricultural Research Service, Bugwood.org

The Asian citrus psyllid has moved to San Francisco. A single specimen of the invasive pest that feeds on citrus leaves and stems was spotted in the city’s Marina district, prompting a citywide quarantine, according to a story by Lauren Hernandez published in the San Francisco Chronicle.

This pest is of such concern because it has the potential to decimate the state’s citrus growers as well as residential yards that contain the trees. When the pest feeds, it can infect trees with a bacteria that causes the deadly Huanglongbing disease.

No more than one-eighth-inch long, Asian citrus psyllids are brown and yellowish-orange winged insects that produce a white, waxy substance while feeding on citrus leaves and stems. In recent years, the tiny-yet-deadly invasive pest migrated north from Southern California, reaching the greater Bay Area in January of 2016, Hernandez reported. This prompted officials at that time to declare temporary widespread quarantines spreading more than 100 square miles.

Once infected, citrus trees produce “bitter, misshapen fruit and eventually die,” public health officials said in a statement, according to the story. The bug also threatens curry leaf trees.

Under the new quarantine rules, the story states, San Francisco retail nurseries are required to sell only those citrus trees that have been treated for Asian citrus psyllids and must be prominently tagged with blue “quarantine” tags, officials say. Citrus fruits can continue to be sold at farmers’ markets, flea markets and swap meets as long as the stems and leaves were plucked before transport.

San Francisco citrus fruit vendors are also required to obtain a compliance agreement from the California Department of Food and Agriculture, according to Hernandez. City residents with citrus trees on their properties are prohibited from transporting citrus fruit or leaves, potted citrus trees or curry leaves outside of the county.

Officials did not say where in the Marina district the insect was detected. They have placed traps throughout the area to determine if there are others. In a statement, officials say they plan to treat citrus host plants within 50 meters of the site where the first insect was trapped, Hernandez reported.

“Even though San Francisco County is not a commercial citrus-producing area, we all play a role in limiting the spread of this insect,” Hernandez quotes San Francisco Agricultural Commissioner Cree Morgan as saying.

People living in the area where the insect was spotted will likely be invited to participate in a community outreach meeting with local and state agricultural officials in the future, officials say, according to the story.

The bacteria the Asian citrus psyllid spreads pose no threat to humans, but the disease it causes in trees and plants is incurable. Huanglongbing disease can kill a citrus tree in five years, according to the UC Division of Agriculture and Natural Resources. Hernandez reported that in a 2017 publication, officials with the UC Davis College of Agricultural and Environmental Sciences stated that Florida citrus groves have been “decimated” by the disease in recent years.

Officials hope the San Francisco quarantine will prevent the tiny pests from hitching a ride on leaves, stems or potted citrus trees and spreading further.