Citrus industry sends out SOS for new disease
Tulare County’s citrus industry put out another SOS as it prepares to stay afloat against an endless sea of obstacles. Fresh off a year that saw a seven-day freeze, multiple finds of the Asian citrus psyllid and a compounding drought, citrus growers will now have to defend the County’s crop from a new disease.
Tulare County Agriculture Commissioner Marilyn Kinoshita gave an informational presentation on the sweet orange scab (SOS) disease at the Feb. 4 Tulare County Board of Supervisors meeting. SOS is a fungal disease of citrus that results in scab-like lesions on fruit rinds, according to the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS). The initial scab forms on very young fruit; it is slightly raised and pink to light brown in color. As the lesion expands, it takes on a cracked or warty appearance and may change color to a yellowish brown and eventually to a dark gray. The scabs typically form a pattern on the fruit like water splashes.
Although there is little affect on internal fruit quality, oranges are severely blemished rendering them unsellable in the fresh produce market. This is a huge problem for the County’s top export crop. The disease can be spread long distances within infected nursery stock and other plant parts. The problem, Kinoshita said, is that the disease is difficult to detect because it has many different looks and variations.
“No two instances of the disease look alike,” Kinoshita said. “You would need lab samples to prove if the fruit is negative or positive.”
SOS is a common disease in South America, mainly Brazil, Argentina and Paraguay. Kinoshita said SOS was first found in the United States on a backyard tangerine tree in Texas in 2010. Since then, it has been detected in Florida, Louisiana, Mississippi, and Arizona.
On Oct. 11, 2013, APHIS confirmed the first evidence of SOS in California on lemon fruit samples collected from two separate commercial groves in Imperial County. APHIS also confirmed SOS on grapefruit collected in a residential area of Los Angeles County and from a commercial grapefruit grove in Riverside County, on Nov. 1, 2013.
Sweet orange and tangerine (including hybrids) varieties are most susceptible. Grapefruit was previously thought to be tolerant of SOS but APHIS confirmed cases of SOS on grapefruit trees in a backyard in Texas.
Kinoshita said SOS can be treated with through a 2-minute “chlorine drench.”. However, she said the levels of chlorination needed to treat the disease has raised concerns about the health of assemblyline workers who might be exposed to the potentially noxious gas.
“We will find out in October whether they will be requiring anything different from us,” she said referring to inspections.
For more information go online to: http://www.aphis.usda.gov/plant_health/plant_pest_info/citrus/sweet_orange.shtml