Grant Information
| Knowledge Area | Subject of Investigation | Field of Science | Percent |
|---|---|---|---|
| 211 - Insects, Mites, and Other Arthropods Affecting Plants | 3110 - Insects | 1130 - Entomology and acarology | 20% |
| 212 - Pathogens and Nematodes Affecting Plants | 3110 - Insects | 1130 - Entomology and acarology | 20% |
| 212 - Pathogens and Nematodes Affecting Plants | 999 - Citrus, general/other | 1130 - Entomology and acarology | 20% |
| 216 - Integrated Pest Management Systems | 3110 - Insects | 1130 - Entomology and acarology | 20% |
| 211 - Insects, Mites, and Other Arthropods Affecting Plants | 999 - Citrus, general/other | 1130 - Entomology and acarology | 10% |
| 216 - Integrated Pest Management Systems | 999 - Citrus, general/other | 1130 - Entomology and acarology | 10% |
The Asian citrus psyllid (Diaphorina citri Kuwayama) has emerged recently as a major threat to citrus in the Western U.S. This invasive insect, which is a vector of the pathogen that causes Huanglongbing disease, is largely an urban problem in Southern California. Management efforts in the region consist of insecticide application in residential settings, production nursery treatments prior to plant shipment to retail nurseries, and quarantine to limit the spread of infested plant material. However, psyllid populations continue to increase in certain areas. Increasingly, homeowners and landscapers will be responsible for managing their own citrus trees to limit damages, and retail nurseries must take a more active role in psyllid control to ensure D. citri and the pathogen, should it arrive, are not disseminated to other parts of the state. Therefore, mitigating the potential impact of D. citri and Huanglongbing in California hinges on the development of a robust educational outreach program in these urban areas. We will develop a monitoring and extension program that targets urban infestations of Diaphorina citri to refine existing control measures. This will include monitoring and extension activities for residential settings to ensure widespread adoption of sound management practices. We will also conduct monitoring and extension activities for retail nursery employees to limit the role these businesses play in inadvertently facilitating vector or pathogen spread. This work will enhance IPM of D. citri and constrain its spread in California, potentially delaying or at least ameliorating some of the impact of Huanglongbing establishment.
The invasive Asian citrus psyllid (Diaphorina citri; ACP), a vector of the bacterium that causes Huanglongbing (HLB) disease in citrus, has emerged as one of the primary threats to California agriculture. This pest readily feeds on citrus and close relatives, on which it can achieve extremely high population growth rates. Damage from ACP occurs due to preferential feeding by the nymphal stages on developing citrus shoots. More importantly, ACP is also an efficient vector of the pathogens (Candidatus Liberibacter spp.) responsible for HLB or citrus greening disease. These diseases produce progressive mottling of leaves, deformed and off-flavor fruit, plant stunting, and eventual plant death. There is no known cure for infected trees. Areas affected by HLB have incurred significant economic losses via reductions in fruit quality and extensive tree mortality, coupled with increasing costs of vector and disease management. In Florida, the psyllid and HLB spread was assisted unintentionally by movement of nursery plants, spreading the psyllid throughout that state in less than three years. ACP invaded California in 2008 and the first case of HLB was found in the Spring of 2012. Currently, ACP is largely an urban problem in the state, with well over 97% of finds occurring in urban or suburban areas. Efforts to control urban infestations have relied on targeted insecticide application applied by the California Department of Food and Agriculture, wholesale nursery treatments prior to shipment to retail nurseries, and quarantines to prevent movement of infested plant material. The efficacy of these treatments at providing sustained control has not been evaluated, nor has their compatibility with recently initiated releases of a psyllid biocontrol agent, the parasitoid Tamarixia radiata. Moreover, although the psyllid is under control in some areas, in others areas control efforts have failed and new strategies are being developed. In some regions the general public will need to take a greater role in psyllid control. In addition, retail nurseries need to take an active role in managing ACP and HLB host plants to ensure that shipments do not introduce psyllids or HLB into new areas. Thus, mitigating the potential impact of ACP and HLB in California hinges on the development of a widespread educational outreach program that includes robust recommendations for psyllid and HLB management in urban settings. We will develop a monitoring and extension program that targets urban infestations of ACP to refine existing management. The will include five objectives:
This project brings together a multidisciplinary team of researchers, extension educators, industry outreach coordinators, and regulators to refine monitoring and extension efforts in the region. This project will be leveraged against other efforts by researchers, the citrus industry and regulators, which will collectively improve the chances of constraining the spread of D. citri and establishment of HLB in Southern California. For the first objective we will conduct detailed monitoring of D. citri, natural enemies, chemical treatments, and any initial evidence of HLB in residential areas. Monitoring will occur in areas that differ in psyllid pressure and parasitoid abundance, and will be evaluated pre- and post-insecticide treatment. These data will provide estimates of natural enemy impact, psyllid reinvasion interval post-treatment, and the interaction of the two factors, which will inform regulatory decisions and homeowner practices. The second objective will consist of developing an extension education program for residential areas. This program will target Master Gardeners, landscapers, and homeowners through a series of training sessions, print material and an online course designed to educate them on D. citri, natural enemy, and HLB identification, biology, and control. For the third objective we will monitor D. citri and insecticide concentration in host plants at retail nurseries. This work will evaluate how treatment history and nursery practices affect psyllid infestations, which is important for understanding whether additional regulations are needed to ensure that retail nurseries do not act as vector or pathogen sources. The fourth objective will consist of developing an extension program for retail nurseries. This program will include initially interviews of nursery employees on their practices that may affect insecticide efficacy and contribute possibly to psyllid and pathogen spread. Afterward we will implement a combination of training sessions and an online course on D. citri and HLB identification, biology, and control. For the final objective we will evaluate the impact of the two parallel extension programs on stakeholder knowledge and adoption of recommended control measures. Pre-and post-attendance surveys for online classes and training sessions will be used for short-term assessment of stakeholder knowledge of learning objectives. Surveys over the duration of the project will be used as a longer-term assessment of changes in stakeholder adoption of recommended practices for psyllid and disease management.
Target Audience
The focus of this project is on urban and suburban infestations of the Asian citrus psyllid in Southern California. The two most significant dimensions concerning psyllid infestations in this area are residential citrus and retail nurseries and garden centers. Therefore, our primary target audiences have been homeowners, Master Gardeners, and nursery employees. However, some of our outreach efforts have included the participation of state regulators, agricultural commissioner officers, commercial citrus growers, and nursery industry representatives.
Changes / Problems
Nothing Reported
Training & Professional Development
Again, over the last year, the project has included training and professional development opportunities for laboratory staff, undergraduate students, and a postdoctoral researcher. Training in technical skills, such as insect and plant identification and laboratory methods (e.g., ELISA) was provided to twopart-time undergraduate helpers as part of the residential and nursery inspections. The project also contributed to the professional development of a postdoctoral researcher by facilitating their attendance and oral or poster presentations at regional, national, and international conferences (e.g., Entomological Society of America, International Research Conference on Huanglongbing).
Dissemination Streams
As noted in the accomplishments report, the project participants have collectively made numerous extension presentations to homeowners and Master gardeners throughout California. The Master Gardener and nursery online training classes, extension publications, websites, and blog have extended that ability to reach other audiences as well. In addition, the results of the monitoring work have been featured in scientific conferences at the regional (e.g., Southern California Entomological Society, Pacific Branch ESA), national (e.g., ESA and EntSoc), and international level (e.g., International Research Conference on Huanglongbing).
Next Reporting Steps
Nothing Reported