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Florida Pioneers Biocontrol as Solution to Citrus Greening

June 9, 2014

U.S. Producers cheered by USDA plans to expand release of parasitic wasp

Division of Plant Industry

Division of Plant Industry

Citrus growers across the nation, and particularly in California, hailed the U.S Department of Agriculture’s recent announcement that it will spend $1.5 million for efforts to breed and release a tiny parasitic wasp in three states: California, Florida and Texas. The wasp, Tamarixia radiata, will help slow the spread of huanglongbing, or citrus greening, in citrus-producing areas of the U.S.

The disease, which has killed thousands of citrus trees in Florida, is now threatening California’s citrus industry and other citrus-growing regions across the U.S. There are full and partial quarantines in place in at least 14 states and U.S. territories.

GreeningonCitrus

Oranges display symptoms of citrus greening.

Florida has been a pioneer in the use of the wasp to slow the spread of citrus greening. Officials here began a biocontrol program in 1998 after laboratory tests by the Florida Department of Agriculture’s Division of Plant Industry showed T. radiata could kill 90 percent of presented citrus psyllid nymphs. By the early 2000s, T. radiata had been established statewide. In the past 10 years, DPI has continued to  import, study and release several biotypes of Tamarixia from throughout Asia, where they occur naturally alongside their psyllid host.

The parasitic wasp, Tamarixia radiate, is a natural enemy of the psyllid that spreads citrus greening.

The parasitic wasp, Tamarixia radiate, is a natural enemy of the psyllid that spreads citrus greening. (Photo courtesy of UF-IFAS)

The use of the biocontrol agent against the psyllid is only one tactic being employed against greening. Growers also use insecticides to combat ACP and these sprays destroy beneficial insects like T. radiata as well as the ACP. That means periodic releases of the parasitoids are needed to supplement populations between sprays, during flush cycles and during tree bloom — all periods when insecticides should not be used in order to allow bees to safely forage on the flowers. Releases of the beneficial wasp are coordinated with and complement growers’ spray schedules.

The beneficial wasps are released throughout Florida in conventional, certified organic and abandoned groves, as well as residential areas where dooryard citrus is grown, in an effort to benefit all growers. Florida Department of Agriculture and Consumer Services inspectors identify hot spots where psyllid counts are consistently or periodically high and mark those areas for releases.

Department employees currently scout about 6,000 blocks of citrus throughout the state on a three-week cycle to collect data regarding ACP populations. With permission of landowners, FDACS employees monitor ACP populations in areas where the wasp has been released to monitor the effect.

The biological control program is part of a comprehensive integrated pest management strategy that includes pest/tree scouting, mechanical, chemical and biological control — all valuable elements of a program to control ACP.

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