2015-2016 Pepper Commission Call for Research Proposals
Project Title: Understanding of psyllid biology and development of tools for long-term control.
Project Year: August 1, 2015 to July 31, 2016
Project Leader: Clare Casteel, Department of Plant Pathology, One Shields Ave, University of California, Davis, CA 95616, phone 530-752-6897; email email@example.com
Psyllids are signiffcant threats to California pepper production. The tomato/potato psyllid and the diseases it vectors have resulted in millions of dollars of loss to Solanaceous crops. Tomato/potato psyllids (Bactericera cockere/10 can directly impact pepper production in several ways: 1) psyllids produce copious amount of honeydew waste resulting it molding of fruit, 2) feeding by insects induce wilting in plants, 3) immature insects cover fruits, resulting in product that is unsuitable for the fresh market, and 4) psyllids vector Liberibacter psyllaurous (also known as L. solanacearum) during feeding. Currently, management is based on intensive monitoring and chemical control of psyllid populations. However, maintaining effective control is difficu lt due to frequent insecticide resistance and a lack of understanding of basic psyllid biology .
Psyllid host ranges are rapidly spreading in California. While psyllid populations are wide spread in Southern California, recently, large numbers of psyllids were found in Solano and San Joaquin Counties (G. Miayo and 8. Aegerter, Solano and San Joaquin County Farm Advisors, personal communication), indicating the host range of the insect may be expanding. Although psyllids have been major pests of California for decades, the basic biology of insect-plant interactions and factors influencing host plant susceptibility and outbreak are still poorly understood. Collectively, this suggests psyllids are a considerable risk and a better understanding of their biology and development of tools for long-term control is needed now, before substantial loss occurs.
Solutions and Significance:
By increasing the basic understanding of psyllid-plant interactions and factors influencing host plant susceptibility to psyllids, alternative control strategies can be developed and utilized in IPM programs. Improved control strategies not only contribute to food security and agricultural technology, but will also reduce pesticide use and thus increased food safety . Therefore, the research proposed in this project will support long-range improvements in the sustainability and safety of the California pepper industry.
Preliminary Work and Background:
Stress alters plant susceptibility to insects. During each growing season peppers may experience abiotic stress such as drought, heat, and/or pollution, and biotic stress such as pathogens and/or insect herbivores. Significant research has demonstrated abiotic and biotic stress can influence plant susceptibility to insect herbivores. The Casteel lab recently visited fields in Kern and San Joaqu in counties to collect psyllids. Heavy psyllid populations were found on blocks of plants that had been infected with pathogens early in the season (Erwinia and Potato Virus Y , separate fields) . Plants suffering from Erwinia also appeared to be drought stressed. Consistent with these findings, Casteel previously demonstrated that virus infection of plants increases insect fecundity and attraction . Further , another psyllid, the red gum psyllid, prefer drought stressed eucalyptus and have higher reproduction on these plants compared to properly irrigated plants. These results, in combination, suggest tomato/potato psyllids may also prefer stressed plants. Early season stress in pepper fields may determine the severity of psyllid outbreaks later in the season. Psyllid outbreaks may be dampened or inhibited in the field by controlling other pepper pathogens or other stresses, which may not typically cause pepper loss. However, drought, pathogen infection, and herbivory does not influence pepper physiology uniformly. Thus a better understanding of the role of individual stresses in pepper susceptibility to psyllids is needed.
The objectives of this proposal are to:
- Evaluate the role of biotic stress in susceptibility of peppers to psyllid outbreaks.
- Evaluate the role of abiotic stress in susceptibility of peppers to psyllid outbreaks.
- Investigate the mechanisms mediating pepper susceptibility to psyllids.
- Develop strategies and recommendations for psyllid control in pepper production based on findings of this proposal.
Plans and procedures:
1) Evaluate the role of biotic stress in susceptibility of peppers to psyllids outbreaks.
We will measure psyllid preference and performance on peppers challenged with different pathogens and pests commonly found in California pepper fields. Pests and pathogens will be selected with the help of Brenna Aegerter UCCE (Collaborator) and based on recent outbreaks. Psyllid preference will be measured using choice assays. Psyllids will be given equal access to either healthy or infected/infested plants. Insect choice will be monitored over time. Psyllid performance will be measured by examining insect survival and fecundity on both healthy and infected/infested plants. This will allow us to determine if specific pathogens or pests that commonly inflict pepper fields contribute to severity of psyllid outbreaks during the season. If differences are detected, additional trials will be conducted in the field in following years. Pests and pathogens determined as high-risk could be monitored in peppers in the future and appropriate control developed.
2) Evaluate the role of abiotic stress in susceptibility of peppers to psyllids outbreaks.
California has experienced significant drought the past several years. Reduced water availability will stress peppers and may influence psyllid outbreak. We will measure psyllid preference and performance on drought stressed peppers. Psyllid preference will be measured using choice assays as above. Psyllid performance will be measured by examining insect survival and fecundity as above. If differences are detected, additional trials will be conducted in the field in following years. This will allow us to determine if changes to specific cultural practices can be made to dampen severity of psyllid outbreaks during the season
3) Investigate the mechanisms mediating pepper susceptibility to psyllids.
Psyllids may prefer stressed plants due to increased volatile production, making locating the host easier. Stressed plants may also be better hosts, with increased nutrients or decreased defenses. Changes in host plant physiology will be evaluated for susceptible plants identified in 1 & 3. Knowledge of changes in host plants that increase psyllid preference or performance can be monitored in future breeding programs to screen out psyllid susceptibility and used to develop novel control strategies.
4) Develop strategies and recommendations for psyllid control in ˇpepper production based on finding in this proposal
By increasing the basic understanding of psyllid-plant interactions and factors influencing host plant susceptibility to psyllids, alternative control strategies can be developed and utilized in IPM programs. Suggestions based on results from this proposal will be made and could include chemical control of non-psyllid herbivores, use of host plant resistance to specific pathogens on border rows, and/or changes in irrigation practices.
Timetable: Evaluating the role of biotic and abiotic stress on psyllid susceptibility is at least a one-year endeavor. Additional years may be required depending on results .
Budget Request, 2015
Research assistant (50%) $ 22,500
Signed by Principal Investigator 01/23/15
Signed by Department Chair 01/26/15