Study: Psyllid biocontrol poses little environmental risk

02/06/2014 11:26:00 AM
Vicky Boyd

Mark HoddleCourtesy University of California, RiversideMark HoddleA minute wasp that goes after the Asian citrus psyllid, the insect that spreads citrus greening, is safe for the environment and doesn't pose undue risks to other non-target creatures.

Those are the results of federally mandated tests conducted by the University of California, Riverside, on Tamarixia radiata, according to a news release.

University researchers first released the wasp in 2011 as biological control for the psyllid.

Since then, they have released more than 200,000 T. radiata at more than 350 different mainly residential locations in Southern California.

Adult asps lay their eggs in psyllid nymphs. Once the eggs hatch, the wasp larvae feed on the psyllid immatures, eventually killing its host. An adult emerges about 12 days later from the mummified nymph.

Adult females also feed on younger nymphs. A single T. radiata female can kill more than 500 psyllids through direct feeding and parasitism, according to information from the University of Florida.

Research led by Mark Hoddle, director of the university's Center for Invasive Species Research, found the wasp was species specific.

To test its safety, different species of native California psyllids were exposed to the wasp.

Essentially, the wasp was given a choice between Asian citrus psyllids and the non-target natives.

Other tests presented the wasp with just the non-target species.

In only one case was the non-target species parasitized and then at a rate of less than 5 percent.

This was the native potato psyllid, which spreads zebra chip disease caused by a very close relative of the citrus greening bacterium.

Because the parasitism rate was so low, Hoddle said it was unlikely to cause population declines.

There is growing concern over the damage that invasive species cause, and biological control programs don’t want to be causing additional problems through releasing inappropriate agents for the control of invasive pests," he said in the release.



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