The California Department of Food and Agriculture recently expanded a quarantine for citrus across Southern California.
A plant disease that kills citrus trees – called huanglongbing, HLB or citrus greening disease – isn’t harmful to humans, but it is fatal to citrus trees and has no cure.
For related news, see: Why California agriculture regulators are stripping Redlands citrus trees of their fruit
The disease is spread by the pest Asian citrus psyllid as it feeds on leaves and stems. The state is urging homeowners who grow fruit in their yards to help citrus farmers protect trees and their more than $3 billion annual crop.
Asian citrus psyllids are small, brown, winged insects no more than one-eighth of an inch long. They have rapidly ruined orchards in Florida and Texas as well as California.
New this year: Areas of San Diego and Ventura counties are under HLB quarantine. The old boundary was expanded in Los Angeles, Orange, Riverside and San Bernardino counties.
You can find the California Department of Food and Agriculture interactive map of the quarantine boundaries here.
Another quarantine
In 2013, areas of Riverside and San Bernardino counties were under quarantine for another citrus killer, called the Oriental fruit fly.
The adult oriental fruit fly is somewhat larger than a housefly, about 8 millimeters in length. The body color varies but it is generally bright yellow with a dark “T” shaped marking on the abdomen.
You can learn more at cdfa.ca.gov.
The state considers property owners with 25 or more citrus trees commercial growers and they have a separate set of rules for cleaning and transporting.
Those who buy fruit from local citrus stands also need to take precautions.
Symptoms can be reported to a state hotline at 800-491-1899, or by completing the “report a pest sighting” form online at cdfa.ca.gov.
The quarantine rules
Commercial citrus growers and nurseries are most affected by the quarantine and must comply with a permitting process for transportation within and outside the quarantine zones.
Residents with less than 24 trees in the quarantine area can move citrus off their property, but only if the fruit is free of stems and leaves and is properly washed. It is still strongly advised not to move citrus due to the risk of spreading the pest.
Residents also can sell citrus at their home-based stands, but they must clean the fruit, remove all stems and leaves and fill out an agreement with the state.
In the backyard
It is estimated that 60% of Californians have at least one citrus tree in their yard.
Currently, the only way to slow the spread of the disease is to reduce the psyllid that spreads it and to remove trees that are infected.
If you are in an infestation area, it is recommended that you consider applying an insecticide on your trees.
If applying systemic insecticide to soil, make the application during summer or early fall, when roots are active and plants are not blooming or about to bloom.
Learn more at californiacitrusthreat.org.
Pests against pests
The Asian citrus psyllid is attacked by many natural enemies, including two types of wasps that have been introduced to Southern California.
The Tamarixia and Diaphorencyrtis wasps are not harmful to humans and do not eradicate the psyllid, but they help reduce populations.
The Department of Food and Agriculture encourages people to protect the two types of wasps by controlling ants that feed on tubules that Asian citrus psyllids make.
Rapid spread
The Asian citrus psyllid was first documented in California in a residential setting in San Diego County in 2008.
The Citrus Pest & Disease Prevention Committee was established in 2009.
In 2012, the first case of HLB was documented in a residential area of Los Angeles County.
It was found in Orange County in 2018 and San Bernardino County in 2019.
Sources: University of California Agriculture and Natural Resources, California Department of Food and Agriculture, USDA, Californiacitrusthreat.orgPhotos: Californiacitrusthreat.org, USDA
