Managing the psyllid

ACP is currently found only in Southern California. The majority of commercial citrus is grown in Central California. If ACP can be prevented from spreading, it minimizes quarantine and export issues and reduces the threat to Central Valley citrus production. If psyllid populations are kept low wherever they are found, their chances of picking up the HLB pathogen are reduced and disease spread is slowed.

Citrus database for rapid pest response

The geographical information systems team at the UC Kearney Agricultural Research and Extension Center in Parlier, in collaboration with the Citrus Pest and Disease Prevention Program, is developing a geographic database that will provide treatment coordinators with information to ensure quick action when psyllids or HLB are found. The database is enriched with details about the citrus groves including ownership—types of trees, conventional or organic management, and who is packing the fruit. In addition, it will identify factors that could influence the direction and speed of ACP spread, such as weather patterns and traffic corridors. “If there is an ACP or HLB find, we can use the database to assess the risk of spread into urban areas and commercial citrus,” said Kris Lynn-Patterson, the GIS coordinator who is leading the project.

Building a better ACP trap

Anandasankar Ray, professor in the Department of Entomology at UC Riverside, is testing olfactory neurons in the antennae of ACP to screen hundreds of chemicals as possible attractants and/or repellents. Attractants added to the standard yellow sticky trap would make a more efficient trap for improved detection and monitoring of psyllids and could eventually lead to an “attract and kill” product. Repellents could also be used as a spray to protect citrus trees.

Treatments for organic citrus farms

Treatment options for homeowners and farmers who do not use synthetic pesticides on their citrus are being explored by scientists with UC Cooperative Extension. The current recommendation for organic growers is to spray a low rate of oil on trees at 14-day intervals. Beth Grafton-Cardwell, UCCE specialist in the Department of Entomology at UC Riverside, is evaluating the effect of this treatment on citrus health, productivity, and fruit quality for San Joaquin Valley navel oranges. Jim Bethke, UCCE advisor in San Diego County, is screening additional organic insecticides on a greenhouse colony of ACP to find products that may have greater persistence and efficacy against ACP.

Introducing natural enemies for biological control of ACP 

Mark Hoddle, UCCE specialist in the Department of Entomology at UC Riverside, collected two natural enemies of ACP in Pakistan. These two tiny wasps, Tamarixia radiata and Diaphorencyrtus aligarhensis, lay eggs underneath or inside ACP nymphs; the hatching larvae eat the nymphs, killing them. Hoddle released T. radiata in Southern California in 2012 and is monitoring its establishment and distribution. D. aligarhensis releases are expected in mid 2013. The natural enemies won’t eradicate ACP, but scientists predict they will reduce densities of the pest in urban areas, giving other control practices a better chance of working. Richard Stouthamer, professor in the Department of Entomology at UC Riverside, is developing optimal methods for mass-rearing ACP parasitoids, determining the relationship between the numbers of parasitoids released and the rates of establishment, and the impact of parasitoids on ACP populations.

Protecting trees in California plant nurseries

In Florida, ACP was not controlled and it quickly spread on nursery shipments of citrus and orange jasmine that were planted in homeowner backyards. Officials are working proactively to prevent a similar scenario in California. Production nurseries regularly ship young citrus trees in small containers to retail nurseries and outlets. Frank Byrne, associate research entomologist, and Joe Morse, professor, both in the Department of Entomology at UC Riverside, are studying the efficacy of the systemic pesticide imidacloprid. “The treatments can protect the young trees for up to three months,” Byrne said. Because retail outlets do not apply pesticides in their facilities, plant protection using chemical pesticides must take place before they leave the production nursery. “Many of the treatments are providing good protection,” Byrne said. “One concern is that if trees are kept in stores for extended periods of time, the level of protection starts to diminish.”