Wednesday, October 23, 2013
A small insect carries the potential to kill San Diego County's commercial citrus industry. The Asian citrus psyllid is capable of spreading a disease that could wipe out a decades-old fixture of San Diego County's agricultural landscape.
SAN DIEGO When Warren Lyall surveys his Pauma Valley Orchards, he sees four generations of his family's work.
His gray hair is tucked under a worn brown baseball cap. His speech is carefully measured like the mix of mature and young trees here, already heavy with oranges. Lyall pulls a pruning tool from his back pocket and leans over a 4-foot tall tree that looks more like a bush.
"This young cara cara naval tree is about 2 years old, 2-and-a-half years old. You can see it's growing with a lot of fresh new growth," said Lyall.
And that fresh new growth is a tender delicacy for a small insect called the Asian citrus psyllid.
"This is where the psyllid loves to live," Lyall said. "This is the only place where the psyllid lays it eggs and the young will begin to grow (here)."
Lyall is an expert on the psyllid because it feeds on the same trees that are his livelihood.
"They'll land on that leaf and they have a sharp mouth part that they literally poke into the leaf and suck the fluid out," Lyall said.
That sounds bad, but it is not the real threat to these citrus groves. The threat to the region's $80 million citrus industry comes from interaction: Psyllids feed on many trees and they can pick up a disease from one tree and carry it to another.
The infection he is concerned about is huanglongbing disease.
HLB kills citrus trees within a few years of infection. There is no treatment. There is no cure.
"We are concerned that disease may become a death knell for our citrus industry in California, which it has become in Florida and many other places in the country," Lyall said.
Florida is dealing with widespread HLB infection. Nearly every county with citrus trees has infected groves. A University of Florida study concluded the disease is imposing a nearly billion-dollar-a-year hit to that state's economy because fewer oranges are making it to market.
Eric Larson is the executive director of the San Diego County Farm Bureau. He said the economic footprint is smaller here, but the situation is just as serious for growers. Farmers are already thinking about a future without citrus trees, Larson said, but replacing them with another crop may not be so easy.
"The citrus trees are on the floor of the valley. San Pasqual Valley, Pauma Valley, Pala-area — where it is cold. Because the citrus trees can handle the cold," Larson said. "And the avocado trees are on the side of the hill, where it's much less cold. You can't remove citrus trees and then plant avocados."
Local citrus farmers are mobilized, and according to Larson, they are attacking the psyllid population with pesticides and insect predators. Keeping the insect's numbers low controls the risk of infection, but the disease may already have a foothold, Larson said, and it is not because of the commercial citrus industry.
"There could be more citrus trees in backyards in a place like San Diego County than there are in the commercial groves, because everybody who has a residential lot has a lemon tree or a lime tree or an orange tree," Larson said. "It is just such a common thing to have. These could become the reservoirs of the disease."
Battling the bug in backyards falls squarely on the shoulders of Tracy Ellis. She is an entomologist with the San Diego County Department of Agriculture, Weights and Measures.
Ellis inspects the leaves of an orange tree in an Escondido yard. She knows there are psyllids here, but it still took her a few minutes to find them.
"Here are some adults right here on the back of this leaf," Ellis pointed out. "And they're small and they always sit at a 45-degree angle from the sub-straight."
Trained eyes can have trouble finding them, so it is even easier for homeowners to miss the threat.
"I think we've probably gotten a little lazy in checking for pests in our backyards, on our citrus tree," Ellis said.
She is working with researchers, farmers, state officials and residents. However, Ellis concedes it is not easy to identify the threat. Even diligent homeowners can miss it. Ellis said It is even harder to tell if a tree is infected with HLB. The infection devastating Florida's citrus industry likely started in a backyard.
"And they didn't really know that there was an infected curry plant, which is in the same family as an orange, in somebody's backyard that they had brought from probably Asia," Ellis said. "That had the disease in it and once the vector is there then the disease spreads."
Researchers attacking the psyllid infestation believe the bug is firmly established in Southern California. With the bug here, there is also suspicion that HLB is here, too.
Warren Lyall thought it was a question of when — not if — HLB will start killing local trees. Growers hope their efforts to combat the psyllids buy enough time for scientists to find a treatment or a cure.