A scourge of insects could decimate Tulare County citrus, 250 psyllids found in Visalia

The Asian citrus psyllid is barely visible to the naked eye, but this tiny insect represents a huge existential threat to Central Valley citrus growers. 

Ag officials discovered more than 250 specimens feasting on citrus trees growing near downtown Visalia last week.

While the psyllid feeds on citrus leaves and stems, it's relatively harmless on its own, according to assistant Tulare County Ag Commissioner Tom Tucker.

The same can not be said for Huanglongbing, or citrus greening, a devastating citrus disease caused by a bacteria that can live inside the insect.

"Once a citrus tree is infected with (citrus greening), it will die," Tucker said. "There is no cure." 

The disease makes fruit taste sour and pithy while its leaves begin to yellow and whither — essentially rotting the tree from the inside out.

More:Spraying for Asian citrus psyllids begins in Tulare

Will dogs save the California citrus industry?

California citrus growers get help from State to fight citrus pest and disease

Fortunately, no evidence of citrus greening was found in the affected Visalia trees, Tucker said.

"We are waiting for official results from the lab, but so far there has been no indication of greening disease," he said.

Tucker works with the California Department of Food and Agriculture to set up to 16 sticky traps per square mile across Tulare County. The traps help to detect the presence of psyllids and other exotic pests that could wreak havoc in the nation's second-largest ag economy.

The near-microscopic bugs have already cost the citrus industry in Florida. When the psyllid made its first U.S. appearance en masse there in 2004, an estimated $4 billion and as many as 8,000 jobs were lost, according to a University of Florida study.

"That's why it's critical that California makes (psyllid) control a No. 1 priority," said Carolina Evangelo, a spokeswoman for the Citrus Research Board here in Visalia.

An economic impact report conducted by the board found that citrus greening could cost the state $7.2 billion in losses if it spread to commercial orchards.

The citrus board has dedicated $40 million in funds over the past 10 years to combat the psyllid. It currently has about 50 projects in development to curb the spread of the disease and eventually find a cure.

"California citrus is one of the largest fresh-fruit industries in the world," Evangelo said. "If our citrus were harmed in any way, its effects would ripple out and be felt around the world."

One of the board's most promising efforts is called "biological control," a form of natural pesticide that relies on insect warfare rather than chemicals.

The citrus board partnered with researchers from UC Riverside to bring Tamarixia, a gnat-sized wasp found all the way in Pakistan, to control the Central Valley psyllid population.

Evangelo says the wasps are an effective, natural predator of the psyllid.

The wasps lay their eggs underneath baby psyllids, or nymphs. When the wasp eggs hatch, the babies devour the nymph, killing the psyllid before it has a chance to mature and infect citrus.

One east Tulare County citrus grower has been at the forefront of these biological control efforts in California. 

Jim Gorden has grown lemons, oranges and grapefruits in the south Valley for more than 40 years. He and the citrus board have spearheaded efforts to build up the Tamaraxia population in the Valley. 

He said that if his crop were to be infected by psyllids and Citrus Greening, his operation would be "devastated," as would many of the neighboring citrus farms since the pests are incredibly mobile.

Gorden wasn't surprised to find a potential solution to California's biggest citrus threat in the far-reaches of Pakistan, though. He says the U.S. has frequently turned to the Middle East to look for natural predators of its most pressing pests.

As a citrus farmer himself, Gorden says the wasps are ideal because they're a sustainable and low-maintenance form of pest control.

"You don't need any additional inputs once they've been introduced," Gorden said. "Just let them go, and they do their thing."

Gorden says the wasps have "shown promise" locally but are just one part of an integrative pest management regime that includes traditional pesticides.

"The idea is to slow down the spread of the disease until science can catch up with a cure or more comprehensive solution," he said.