Hoddle cautions that the Tamarixia, and another parasitoid called Diaphorencyrtus aligarhensis (Encyrtidae), are not “silver bullets” in the ACP/HLB fight. Nevertheless, they do offer hope. The Diaphorencyrtus aligarhensis could be released later this year as Hoddle awaits U.S. Department of Agriculture approval to release the parasite. While the Diaphorencyrtus aligarhensis works a little differently than the Tamarixia radiate, it nevertheless is another tool in the box of biological control measures officials can use in controlling the ACP.

Commercial orchards will continue to spray for the ACP, but urban environments such as Los Angeles will employ biological control measures because the spray program operated by the state is simply too expensive for the state to continue.

“As long as we maintain well-irrigated urban environments with plenty of citrus in them the Asian citrus psyllid is going to be here to stay,” he said.

That is why these biological control measures remain just that – control measures. Hoddle said he will consider the biological control program successful if it can show a 30 percent kill rate of ACP by the parasitic wasps.

Important in this battle will be control of the Argentine Ant, which is quite protective of the ACP because of the sugary honeydew it secretes as a byproduct of phloem feeding.

According to Hoddle, about 90 percent of southern California is infested by the Argentine Ant, which is also a non-native, invasive pest. In studies across southern California, Hoddle discovered that about 55 percent of ACP colonies are guarded by the ant because it provides an easy food source in the honeydew. In those areas the Tamarixia is only effective in killing about 12 percent of the psyllid population. However, in areas with no ant activity, parasitism jumps to over 91 percent, Hoddle said.

“That’s why I’ve been suggesting to the Citrus Research Board and anybody else who’s been trying to do something with bio control with the ACP that if you want to get the Tamarixia established in an area you might have to go in and pre-treat an area to get rid of the ants,” he said. “You’re just working against yourself if you’re putting out thousands of parasites and the ants are just going to eat them.”

 

An online video published by the Center for Invasive Species Research (CISR) shows Tamarixia being released in southern California. Hoddle is the CISR director.

 

tfitchette@farmpress.com

 

 

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