What is in this article?:
- Recent finds of citrus greening disease in Texas' Rio Grand Valley have the California and Arizona citrus industries on high alert.
- HLB could already be in the Los Angeles basin but not yet detected.
- A top concern for the spread of HLB is the most common paths travelled by the psyllid — along major transportation corridors and U.S.-Mexico border crossings.
RESEARCHERS CHECK yellow sticky traps for the Asian citrus psyllid in a backyard citrus tree.
Two Western scientists hope the two finds of citrus greening disease (Huanglongbing or HLB) in Texas in January will provide valuable information to help the California and Arizona citrus industries prepare for the inevitable outbreak of the deadly tree disorder in the West.
The Texas Department of Agriculture in late January confirmed the state’s first case of HLB in a commercial orange grove in San Juan in the Rio Grande Valley. A second disease find was confirmed days later in a grapefruit grove in the same area.
“Finding Huanglongbing disease in Texas means finding the disease is much closer to California,” said MaryLou Polek, California Citrus Research Board (CRB) vice president of science and technology, Visalia, Calif.
With HLB moving closer to Western groves, California’s citrus industry continues to fight an uphill battle against the disease that already could be present in the Golden State.
“Huanglongbing disease could already be in backyard citrus in Los Angeles,” Polek said.
Large numbers of the Asian citrus psyllid (ACP), Diaphorina citri, the primary vector of HLB, are now in the L.A. basin.
“A single citrus tree in the L.A. basin area can have hundreds of psyllids,” Polek said. Funding shortfalls and large psyllid numbers are why some insecticide treatments in the metro L.A. area have been curtailed.
“It was fighting a losing battle,” Polek said. “The new treatment strategy is designed to re-deploy limited assets to allow the greatest protection for commercial citrus growers. We are concentrating treatments in the outlying areas particularly the corridors leading to commercial citrus.”
Psyllid numbers have exploded in California since the first insect was found in the summer of 2008 in a backyard citrus tree in San Diego County. In 2011, 13,967 psyllids were found in California in many repeat locations, according to Steve Lyle of the California Department of Food and Agriculture (CDFA).
More than 1,200 psyllids were found in the first 20 days of this January alone; 801 insects in Los Angeles County, Lyle says. Almost all of the psyllids have been found in residential citrus.
A few psyllids have been found in traps in commercial groves in Riverside and San Bernardino counties, but not in the major commercial citrus counties of Tulare, Fresno, and Kern.
Candidatus Liberibacter asiaticus is the bacteria associated with HLB disease and can be carried by the psyllid. HLB attacks the citrus tree’s vascular system and reduces water uptake and disrupts plant nourishment.
HLB-infected tree symptoms included mottled and yellowed leaves which can take two to three years to appear. The fruit can become misshaped, bitter tasting, and unmarketable.