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- UC scientists began releasing parasitic wasps, a natural enemy of the Asian citrus psyllid, to help control an invasive pest that could be devastating for the state’s $1.1 billion citrus industry and citrus trees in residential landscapes.
Hoddle said Tamarixia won’t eradicate Asian citrus psyllid, but scientists predict it will reduce the densities of the pest, giving other control practices a better chance of working. Commercial citrus producers in California will still need to apply insecticides to control Asian citrus psyllid and prevent the spread of Huanglongbing, should it be found in the state. However, the frequency of these applications may be reduced because Tamarixia is killing ACP nymphs in areas that are not sprayed.
Hoddle collected the parasites in collaboration with scientists in the Department of Agri-Entomology at the University of Agriculture in Faisalabad (UAF), Pakistan. UAF was an ideal base for the project, Hoddle said, because it had citrus research plots infested with Asian citrus psyllid that have not been treated with insecticides. The university is also situated near local commercial citrus production, the area has a climate similar to citrus-growing regions of California, and the university’s vice chancellor, Iqrar Khan, is a UC Riverside graduate who also has an active research program on Huanglongbing in Pakistan.
In March and April 2011, Hoddle spent four weeks at UAF to set up research plots in kinnow and sweet orange trees. Coincidentally, kinnow is a mandarin that was bred at UC Riverside in 1935 and accounts for 85 percent of citrus produced in the Punjab. Hoddle and his Pakistani colleagues collected 24 male and 56 female Tamarixia radiata, which were brought back to UC Riverside to establish colonies.
Hoddle returned from a June 2011 trip to Pakistan with 151 male and 255 female Tamarixia radiata. An October and November 2011 visit netted another 800 parasitic wasps.
“Gathering insects from citrus plants in the Punjab generated an immense amount of curiosity,” Hoddle said. “Kids in particular were super-curious about what we were doing, where we had come from and why we had come to Pakistan. The people in the Punjab were incredibly courteous, polite and generous.”
Hoddle has trained a Pakistani graduate student Shouket Zaman Khan at UAF to monitor the interaction of Asian citrus psyllid with its natural enemies in their native environment. The researchers will determine whether other natural enemies of the pest could provide additional biological control of California ACP in the future.
Funding for the Asian citrus psyllid biocontrol effort has been provided by the California Department of Agriculture Food and Agriculture Specialty Crops Program, the USDA Citrus Health Response Program, the Citrus Research Board, and the UC Hansen Trust.