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Year in Review: Biocontrols help retard spread of Citrus Greening

December 26, 2013

Asian citrus psyllid biological control program expands

Scientists at the FDACS Division of Plant Industry are rearing two parasitic wasps that are natural enemies of the Asian citrus psyllid (ACP) Diaphorina citri. The Asian citrus psyllid is the most serious citrus pest because it transfers the bacteria that causes citrus greening disease (Huanglongbing or HLB).  The Bureau of Methods Development and Biological Control at DPI is raising the wasps, Tamarixia radiata and Diaphorencyrtus aligarhensis, for classical biological control of the ACP.  Both wasp species kill immature psyllids through parasitism and host feeding. These parasitoids have helped reduce populations of the psyllid worldwide.

Citrus greening was first detected in Florida in Miami-Dade County in September 2005 and is now present in all citrus-growing counties. The disease leads to decline and eventual death of citrus trees. There is currently no known cure.

The Division of Plant Industry and the University of Florida imported both wasp species from Asia in 1998. After quarantine testing was complete, DPI began releasing T. radiata in 1999 and D. aligarhensis in 2000, before HLB was present in Florida. The Gainesville DPI lab currently produces approximately 1.5 million T. radiata and 60,000 D. aligarhensis per year. The majority are released throughout the state with the remainder sent to researchers from various organizations. Of the two known ACP-specific parasitoids, only T. radiata has established and is widespread.

A grapefruit with symptoms of citrus greening

A grapefruit with symptoms of citrus greening

In September of this year, the Methods Bureau began mass-producing these natural enemies of the Asian citrus psyllid in a newly renovated facility in Dundee. As the facility increases parasitoid production, large numbers of wasps will be hand-delivered or shipped for field release throughout citrus-producing regions of Florida.

Field release of parasitoids requires a systematic and coordinated approach to ensure biocontrol agents are being released in areas with the highest current need and are best utilized for the benefit of all citrus growers in Florida. Release sites will be identified and sorted using an online mapping system consisting of numerous layers including conventional citrus, certified organic, abandoned groves, and dooryard citrus. Releases will be arranged to complement existing Citrus Health Management Areas to target current greening hot spots and to avoid releasing wasps in areas that will soon be receiving coordinated sprays.

It is encouraging to see more weapons added in the war against citrus greening.

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