UCR leads efforts to eliminate citrus pest

The usage of parasitic wasps by UC Riverside scientists is among the most recent and innovative strategies implemented in the fight against the Asian Citrus Psyllid (ACP), a highly problematic agricultural pest. The release of the parasitic wasps marks the first time that these creatures have been introduced to California. “We anticipate that over the next year or so thousands of these parasitoids from Pakistan will be released throughout Los Angeles, Riverside and San Bernardino counties and other areas as the pest continues to spread. Once [the wasp species] establishes, it will move and find new populations of ACP to attack and kill,” stated UC Riverside Professor and Director of the Center for Invasive Species Research Mark Hoddle in an article by the UC Riverside Newsroom. Hoddle and his wife, Christina Hoddle, have spent the past year traveling to Pakistan in order to obtain and study the parasitic wasps whose release was recently authorized by the state and federal government.

Mark and Christina Hoddle received widespread recognition last September when their endeavors in Pakistan were chronicled by the Los Angeles Times. The release of the 281 parasitic wasps, a natural enemy of the ACP, represents the finale of months of research—most of which were spent in quarantine in order to prevent any premature release of the wasps.  This research was predominantly aimed at examining the effectiveness of the wasps along with proving that the wasps did not pose any unjustifiable environmental hazards. “It’s like releasing the genie out of the bottle. You can never get it back in…We don’t want our good guy to wipe out another good guy,” stated Mark Hoddle in a Los Angeles Times article, addressing the concern that the wasps could potentially harm other insects.  Hoddle, alongside numerous other UC Riverside faculty administrators including Executive Chancellor Dallas Rabenstein, were present during the official release of the wasps that took place on the morning of Dec. 20.  The wasps were contained in glass vials that were tied to the branches of citrus plants and were subsequently released by administrators. “This is very good news for the integrated management of Asian citrus psyllid and a highly significant contribution of the University of California. Parasitoid releases will add a new and exciting component to the management program for ACP, especially for the many homeowners who have citrus trees in their yards,” stated citrus Entomologist Elizabeth Grafton-Cardwell in a UC Riverside Newsroom article.

The tiny parasitic wasps (1/16 of an inch in length) can eliminate the threat posed by the ACP since female wasps and their larvae feed on the younger population of the ACP in their nymph stage. The ACP has been the focus of much research due to its costly impact on the citrus industry. The ACP is responsible for over one billion dollars worth of damage to California’s agriculture and is also prominent in Florida, Arizona, Texas and several other states. The insects are carriers of a bacteria that causes Huanglongbing disease, which makes citrus fruit unfit for retail by means of bitter juices, smaller sized fruit and other irregularities. The most significant threat, however, lies in the fact that the disease currently has no cure and eventually results in the death of the entire plant.

The wasps are intended to serve as a supplement to the usage of insecticides, although officials anticipate that the citrus industry may be able to decrease their dependency on insecticides once the wasps become widespread.  Chancellor White expressed his hope regarding the new strategy in Dec. 9’s Friday email, stating, “ When we know for certain that Tamarixia will control the psyllid, spraying with insecticides can be stopped. Good for us. Good for California. Good for the worldwide citrus industry.”

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