A SPECIAL GROWERS’ REPORT OF AG ALERT ® CALIFORNIA Trees & Vines
Natural enemies prove effective against citrus pest By Bob Johnson California citrus growers anxious about a potential outbreak of citrus greening can breathe a little easier. HLB arrived in Florida in 2005 and has since destroyed the state’s commercial citrus pro- duction. By 2009, Florida citrus growers had removed 60,000 acres of citrus trees because of the disease. By 2022, Florida citrus acreage had declined by 75%. During a 2010 trip to the University of Agriculture Faisalabad in Pakistan, Mark Hoddle, right, a biological control specialist with the University of California, Riverside, documents success of the Tamarixia radiata wasp, a predator of the Asian citrus psyllid, which spreads citrus greening, a disease that kills citrus trees. He introduced the wasps in California to protect the citrus crop.
In California, the psyllid was first detected in San Diego County in 2008. Four years later, a residential citrus tree in Los Angeles County was found to be infected with huanglongbing. Last September, the presence of an Asian citrus psyllid carrying HLB was confirmed in a residential tree in Ventura County, where about a dozen trees tested positive for the disease. The finding led to a 5-mile quarantine around the infected trees to restrict movement of citrus fruit, trees and plant material. In California, the disease has been limited to urban citrus trees and has not yet infected commercial citrus. Huanglongbing is a bacterium that can kill citrus trees within a few years after gaining entrance to the trees’ vascular system. It causes the fruit to drop prematurely when it is mostly green and not sweet. The Asian citrus psyllid picks up the bacterium by feeding on infected trees and passes it on to additional trees as it feeds. See CITRUS, Page 7
A combination of a parasitoid wasp imported from Pakistan and other natural enemies of the Asian citrus psyllid already present in California has proved effective in fighting the pest, which can spread the fatal and incurable citrus disease, also known as huanglong- bing, or HLB. “Our natural enemies have killed more Asian citrus psyllids than any other manage- ment program,” said Mark Hoddle, University of California, Riverside, biological control specialist who has studied the problem for 15 years. “The control the biocontrol agents are providing is very high, and it is free.” During a UC integrated pest management webinar, Hoddle said he is confident in the effectiveness of biological controls, adding that he believes “it is very unlikely California is going to succumb to the Asian citrus psyllid and huanglongbing problem in the manner Florida did.” “These intensive areawide programs based on insecticides may not be as necessary as we once believed,” he said.
6 Ag Alert July 17, 2024
Powered by FlippingBook