New Greenhouse Facility Opens to Save Citrus from Psyllids that Vector HLB
Facility to Rear Tamarixia Radiata, Natural ACP Predator
By Patrick Cavanaugh, Farm News Director
Scores of citrus industry leaders, citrus growers, scientists and CDFA officials attended the ribbon cutting event TODAY at the opening of a new greenhouse on the Cal Poly Pomona campus to rear Tamarixia radiata, a tiny parasitic wasp imported from Pakistan because it is an Asian Citrus Psyllid (ACP) nymph predator. ACP, in turn, is a serious nonnative citrus pest that can vector Huanglongbing (HLB)—a deadly citrus disease also known as Citrus Greening—that has devastated the powerhouse citrus
industry in Florida, threatens to ruin additional citrus economies, and is the biggest threat the California citrus industry has ever faced.
According to the United States Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS), infected citrus trees “produce fruits that are green, misshapen and bitter, unsuitable for sale as fresh fruit or for juice. Most infected trees die within a few years.” ACPs have been detected in Alabama, American Samoa, Arizona, California, Florida, Georgia, Guam, Hawaii, Louisiana, Mississippi, Northern Mariana Islands, Puerto Rico, South Carolina, Texas and the U.S. Virgin Islands. Of those locations, the HLB disease has been detected in California, Florida, Georgia, Louisiana, Puerto Rico, South Carolina, Texas and the U.S. Virgin Islands.
ENTER: Tamarixia radiata
Use of the ACP predator, Tamarixia radiata as a biological control for ACP was discovered by Mark Hoddle, biological control specialist and principal investigator, UC Riverside ( UCR), Department of Entomology. The first release of Tamarixia was in December 2011 after USDA-APHIS cleared the natural enemy for release from the Quarantine Facility at UCR.
“Tamarixia can kill ACP nymphs in two different ways,” explained Nick Hill, a Tulare County citrus producer and Citrus Pest & Disease Prevention Program (CPDPC) chair. “The first is parasitism. In this instance, a female parasitoid lays an egg underneath a fourth or fifth instar—the larger and final developmental stage of the ACP nymph before becoming an adult—nymphs that are most preferred by Tamarixia for parasitism. When the egg hatches, the Tamarixia larva begins to feed on the under-surface of the ACP nymph. Eventually the larva completely excavates the body cavity of the ACP nymph and pupates inside the empty shell of its host.”
Hill explained the first releases of the tiny and harmless wasp will occur this fall in urban areas, “to help control ACP so that we do not have to do mitigations such as spraying in those areas. We hope to get to a point where we no longer need to go into people’s yards and ask if we can treat the trees.”
“The issue,” commented Valerie Melano, professor and chair, Cal Poly Pomona Plant Sciences and interim chair, Cal Poly Agribusiness & Food Industry Management/Agricultural Science, “is that we need to come up with the best possible ways to raise enough wasps for big releases to prey on ACP. We will have CDFA employees working in this green house, as well as student workers who have participated in our research program all along,” noted Melano.
Hill added, “The idea is to get enough Tamarixia out there so they start reproducing themselves and they become self sufficient. This is tough to accomplish, but researchers think if they can get big numbers of the wasp into the urban areas, they can put a big dent in lowering the populations of ACP.”
Cal Poly Pomona Greenhouse
The new Cal Poly 5,040-square-foot research greenhouse, built in collaboration with Citrus Research Board and constructed through a $400,000 grant from the Citrus Pest & Disease Prevention Program, will house the second Tamarixia production program in California. CDFA’s Mount Roubideaux facility in Riverside houses current production. Both facilities will support the CPDPC biological control program that oversees releases in urban areas with high ACP populations.
The California Department of Food and Agriculture (CDFA) operates an extensive monitoring program to track the distribution of the insect and disease in both residential areas and commercial citrus groves. Results have determined quarantine zones, guided releases of biological control agents, and prioritized areas for a residential chemical control program. Nearly all of southern California is under quarantine for ACP, due to the fact that more than 15 residential trees have been discovered to be in infected with HLB.
The ACP quarantine in California includes parts of the following counties: Fresno, Kern, Kings, Madera, Monterey, San Benito, San Joaquin, San Luis Obispo, San Mateo, Santa Clara, and Stanislaus; and the following entire counties: Imperial, Los Angeles, Orange, Riverside, San Bernardino, San Diego, Santa Barbara, Tulare County, and Ventura.