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Integrated Pest Management of the Potato Psyllid and Candidatus Liberibacter Psyllaurous in a Multi-Crop System

Trumble, John
University of California - Riverside
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The primary goal of this proposed research is to provide growers with sustainable strategies for control of the potato psyllid on potatoes, tomatoes and peppers.
  1. Epidemiological studies include the following objectives: a) Determine acquisition and inoculation access time required for potato psyllid to effectively transmit CLp to and induce disease in potato, tomato, and pepper plants, b) Determine susceptibility of different plant growth stages of potato, tomato, and pepper to CLp, c) Determine the correlation between potato psyllid density and disease incidence and severity in potato, tomato, and pepper, d) determine if weed associated with potatoes host the psyllid and/or the pathogen.
  2. Monitoring psyllid populations: a) Determine the within-plant preferences of psyllids at various stages of crop growth, b) Determine the within-field distributions of psyllids and create an efficient sampling strategy for psyllids.
  3. Development of an IPM program based on improved pesticides, and understanding of pesticide resistance, maximizing any beneficial insects present in the systems and between crops, and determining if potatoes lines in CA and potatoes and tomatoes in Texas offer resistance to psyllids.
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Non-Technical Summary: Many sustainable low input IPM strategies for vegetable production are at immediate risk because of the development of large populations of the potato psyllid and the damage associated with the transmission of Candidatus Liberibacter psyllaurous. Losses have been in the millions of dollars in Texas and California alone, and the insect and pathogen have spread to many major potato, pepper, and tomato production areas across the U.S. As a result, growers are applying large amounts of chemical pesticides, particularly organophosphates, carbamates, pyrethroids, and neonicatinoids. We propose to develop sustainable IPM strategies based on improved epidemiological understanding of transmission and alternative non-crop hosts of the vector and pathogen, determination of effective monitoring strategies, and development of IPM strategies using less toxic pesticides and pesticide resistance management strategies, biological controls, and new cultural control techniques. The epidemiological studies will provide critical data on aquisition and transfer of the pathogen. The cultural approach will allow growers to choose the level of cultivar susceptibility and target weed control specifically to the species that harbor the pathogen. Our biocontrol studies include an assessment of the potential for emplyoment of beneficial insects to provide critical ecosystem services in areas outside the crop fields. Our pesticide research will provide environmentally-friendly alternatives to the chemicals under review by FQPA. Finally, our partial-budget analyses will provide the cost-benefit data needed to determine the economic viability of the IPM strategies. This proposal specifically addresses the key RAMP issues of developing and adapting IPM tactics and technologies to address multi-crop problems.

Approach: For the epidemiological studies designed to determine CLp acquisition access time, experiments will be conducted at the USDA-ARS facility where of both Liberibacter-infected and Liberibacter-free potato psyllids are currently maintained. Liberibacter-free psyllid adults will be allowed to feed on Liberibacter-infected potato, tomato, and pepper plants for selected periods of time. After each acquisition access duration, 20 psyllids will be transferred to individual Liberibacter-free potato, tomato, and pepper plants and allowed to feed for 7 days; 10 plants will be used for each acquisition access time treatment. We will also determine susceptibility of different plant growth stages: Field experiments will be conducted in WA, TX, and CA. At each location, Liberibacter-free potato, tomato, and pepper plants in small cages will be exposed to Liberibacter-infected potato psyllid adults under field conditions. We will then determine the correlation between potato psyllid density and disease incidence: field cages will be established in WA, TX and CA. Plants (in pre-bloom stage) in the cages will be exposed to selected different densities (0, 6, 12, 20, 60, 200, and 300 psyllids/cage/crop) of Liberibacter-infected potato psyllids for 15 days. Each treatment will be replicated four times for each crop. Weeds associated with potatoes (CA, TX and WA) and with tomatoes (TX and WA) and peppers (TX and WA) will be evaluated as hosts for psyllids and the pathogen. For Determining the within-plant preferences of psyllids at various stages of crop growth, potatoes, tomatoes and peppers will be planted at university field stations in Weslaco, TX and Orange Co, CA at appropriate times to maximize psyllid populations. These fields will be sampled biweekly for psyllids by systematically examining 40 plants per crop. The approximately 0.5 ha fields will not be treated with insecticides. Records will be recorded from the top (new foliage), middle (mature foliage), and bottom (mature/senescing foliage) of each plant. The within-field distributions also will be calculated. Within-field distributions will be measured to determine if edge effects can be used to predict where populations will first appear in the field. We can then use these data to create an efficient sampling strategy for psyllids. Statistical analyses will follow the established procedures previously published by the authors. An IPM program will then be generated based on the testing and use of novel pesticides, the occurrence of beneficial insects, and evaluation of the percentage of the insects carrying the pathogen. By using of a partial budget economic analysis for potatoes (in CA and TX), and for peppers, and tomatoes (in TX), we will provide critical net profit information for growers and scientists. In addition, we have designed a comprehensive extension/outreach plan designed to change the behaviors of growers that have led to the current overuse of pesticides. We also include educational deliverables that include training of graduate students and post-doctoral scientists.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Antimicrobial Resistance
Pesticide Residues
Bacterial Pathogens
Prevention and Control