Dundee Biological Laboratory expands fight against citrus greening

As new research aimed at turning the tide against the devastating effects of citrus greening on Florida accelerates, the oldest weapon in the state's arsenal is being expanded.

On Feb. 7, a renovated and updated Dundee Biological Control Laboratory in Polk County made its debut to significant fanfare from Agriculture Commissioner Adam H. Putnam.

Since 1998, when the Asian psylid that spreads the HLB disease first arrived in Florida - and seven years before the first case of greening was discovered and reported - the facility has bred and released throughout the state a tiny wasp, Tamarixia radiata, that feeds on HLB psylids, the vector for greening.

The tiny wasps, native to Asia, are harmless to humans, animals and other insects.

Their use was approved in 1999 by USDA's Animal and Plant Health Inspection Service.

The wasps kill psylids in two ways, explained Eric Rohrig, a Florida Department of Agriculture and Consumer Services (FDACS) biological scientist who oversees the Dundee laboratory.

One is called "host feeding." That means the wasp feeds on the body fluids of a psylid. The other is called "parasitism." That means the wasp lays an egg on a psylid larvae. When the egg hatches, the young wasp feeds on the body fluids of the larvae.

In both cases, the psylid is killed before it can reach maturity and spread the greening disease.

The Dundee facility opened more than 30 years ago as part of the Bureau of Citrus Budwood, which is responsible for storing the pure cultivars of all citrus varieties grown in Florida.

In 2007, it became a biological control facility when the budwood facility moved from Dundee to Chiefland "because we wanted that facility to be in a non-citrus growing area so they were not exposed to greening," said Trevor Smith, chief of the Bureau of Methods Development and Biological Control at FDACS.

By then, Smith said, the greening threat was already so pervasive that the budwood had to be moved out of citrus growing areas to protect the purity of cultivars and avoid any chance of infection by HLB.

"We also realized in 2007 that if we were going to mass produce the wasp to combat the Asian citrus psylid, we needed more space than our little laboratories in Gainesville," Smith said. "So we took an already existing property, after we had moved our budwood operation to the new location in Chiefland, and we renovated it into a world-class rearing facility."

Breeding and releasing the wasps is now the laboratory' sole purpose. It is funded under the Citrus Health Response Program (CHRP), via USDA.

Until now, the facility has reared and released 100,000 wasps per month. Over the next year, that number will grow to up to 300,000 per month, Smith said - tripling the program's power to fight greening.

Each wasp can kill hundreds of baby psylids, so at its new production levels, the facility will be capable of killing tens of millions of HLB psylids per month, Smith said.

The wasps are released throughout the state. "But we do have a prioritized list of locations," Smith said. "And the ones we really want to concentrate on are abandoned groves, because they're not being treated. There is no chemical control going on, so an abandoned grove is just a hotbed for the disease. Another focus is organic properties, because they are now spraying a bunch of chemicals, so they need a beneficial insect to attack the psylids. And the third is dooryard citrus (or noncommercial citrus grown in people's yards), and what we call 'problem properties,' meaning one that is not actually abandoned, but one that has fallen on hard times."

In particular, Rohrig said, current focus is on identified "hot spots." Each week, about 100 scouts from the Bureau of Pest Eradication and Control are dispatched across the state to monitor 6,000 blocks of citrus trees. Every three weeks, they go back to update their assessments of each area.

"And Central Florida is a big focus for us, because Central Florida has a lot of citrus," Rohrig said. "

Like other key field marshals in the war against greening, Smith said he is confident that in the end, the disease will be defeated.

"The use of these wasps is just another tool," he said. "It's definitely not a silver bullet. But it is another tool we can use to drive the number of psylids down. If we can really drive the numbers down to very small populations, then the spread of greening slows down. And based on that, I agree 100 per cent with others who say we will turn the corner on this disease eventually. We just need to keep the industry alive long enough to get to that point. And I truly believe that releasing millions and millions of these wasps each year will help drive down the psylid population and help us win the battle against greening."