How safe is the enemy of a citrus-threatening pest?
The Asian citrus psyllid (ACP) can spread the lethal and incurable citrus disease known as huanglongbing (HLB) or citrus greening that threatens the multi-billion dollar global citrus industry. In Southern California, large and widespread populations of ACP have been detected in several counties, having arrived, most likely, from Mexico where ACP is widely established.
In 2011, for the first time entomologists at the University of California, Riverside released Tamarixia radiata, a wasp that is the natural enemy of the ACP, in a citrus grove in Riverside to help control the psyllid. But is this wasp safe to use? Does its introduction pose any risk to the environment?
Results from Federally mandated tests performed at the University of California, Riverside now show that Tamarixia radiata is indeed safe for the environment and poses no undue risk to other insects, humans or pets.
“Our work demonstrates that Tamarixia radiata is very specific to the target it is being released to kill — the nymphs of the Asian citrus psyllid in this case,” said Mark Hoddle, the director of the Center for Invasive Species Research, whose lab performed the tests.
Study results appear in the February 2014 issue of the Journal of Economic Entomology.
Safety testing in biological control is important as the release of natural enemies may pose some type of environmental risk. In this instance, Tamarixia radiata were imported from the Punjab region of Pakistan, and tested for safety in quarantine at UCR over an 18 month period.
The study is the first published study designed specifically to determine the host range of Tamarixia radiata. The results are important as the wasp is being used for ACP biological control in Florida, Texas, the Caribbean, Central and South America, and Mexico.
“These types of studies continue to advance the safety of biological control for suppressing populations of invasive pests thereby greatly reducing reliance on pesticides for control,” said Hoddle, a biological control specialist in the Department of Entomology. “In urban areas, initially pesticide treatments were applied to ACP-infested trees, and chemically-treated buffer zones were established around sites to control the pest.”
To test the safety of Tamarixia, different species of native California psyllids were exposed to the wasp in a series of tests. The tests were designed to give the wasp a “choice” between ACP and a non-target psyllid speices, or there was “no choice” (that is, the wasp was only given access to a non-target species, one it had not evolved with). When given a choice, Tamarixia overwhelming attacked ACP, the researchers found.