North American Potato Late Blight Worskshop
Priorities in Research and Education
on Late Blight

William M. Brown, Jr.
Department of Bioagricultural Science and Pest Management
Colorado State University

Background
The North American Potato Late Blight Workshop was held in Tucson, AZ, January 8-11, 1997. More than 200 Canadian, Mexican, and U.S. growers, processors, seed certification specialists, agri-chemical professionals, cooperative extension specialists and researchers met to discuss the state of late blight knowledge, assess needs and prioritize recommendations.

Summary presentations were presented by leaders in 12 topic areas. Subsequent breakout discussion sessions reviewed and defined needs in research and education. From these discussions priorities were defined and ranked. These needs and priorities are presented below.

Recommendation Summaries from Topic Groups
(In many instances the same or very similar priority recommendations were listed in more than one area. In those cases, they are listed in the most appropriate topic area. Discussion group source and rank for all recommendations are shown at the end of each statement.)

General Statement
Encourage the USDA to provide ample and sustained funding for these research and education initiatives on a multi-year renewable basis. In addition, encourage the USDA to establish a special pool of collaborative funds as seed money for innovative ventures between the USDA + States + Commodity Groups + Private Enterprise and other entities to address Potato Late Blight priorities identified by this workshop and the subsequent follow-up on the APSnet Potato Late Blight Workshop.

1---Identification
*Develop economically feasible, rapid, and reliable identification methods, including ELISA, PCR-ELISA, and other emerging technologies, to assay for late blight on site in fields and in storage. (ranked #3 in Identification)

*Develop a quick, reliable and inexpensive late blight diagnostic techniques for laboratory, storage and field use for large numbers of seed potato tubers. (ranked #4 in Regulatory)

*Develop quick identification techniques for tomatoes (transplant and field) that can be used by growers and field personnel.(ranked #3 in Tomatoes and Late Blight)

2---Biology

*Study the effects of abiotic and biotic factors on oospore formation, dispersal, survival, and growth or infectivity. (ranked #1 in Biology)

*Study oospore biology and its importance in disease development. (ranked #2 in Cultural Control)

*Study population structure, dynamics, and stability-genetics, cellular, and molecular biology aspects. (ranked #2 in Biology)

*Study the effects of abiotic and biotic factors on all spore forms associated with tuber rot and soil-borne inoculum. (ranked #3 in Biology)

*Evaluate factors associated with tuber blight development ( in storage and/or in field). (ranked #1 in Cultural Control)

*Investigate the epidemiology of tuber blight, including pre- and post-harvest tuber infection development, effect of leaf blight severity on tuber rot, and development of standard methods of tuber rot assessment. (ranked #5 in Epidemiology)

*Develop effective ways to dispose of infected seed potatoes (also table stock). Evaluate burying, disking, hot spot treatment, survival in volunteer, composting conditions and potential, in reference to both the mycelium and potential oospore development. (ranked #5 in Regulatory)

3---Fungus Genetics
*Identify genotype diversity in P. infestans populations throughout North America. (ranked #1 in Fungus Genetics)

*Develop methods to evaluate role of recombination in generating new fungus types. (ranked #2 in Fungus Genetics)

*Increase host-pathogen genetics research. (ranked #3 in Fungus Genetics)

*Increase efforts to advance studies of basic genetics of P. infestans system. (ranked #4 in Fungus Genetics)

*Develop improved genetic markers for P. infestans. (ranked #5 in Fungus Genetics)

4---Epidemiology
*Evaluate the relative importance of inoculum sources (i.e., cull piles, seed tubers, volunteers, home gardens, etc. and oospores) that initiate epidemics. (ranked #1 in Epidemiology)

*Study primary inoculum sources and their relative importance in disease development. (ranked #4 in Cultural Control)

*Identify the role of late blight infections in tomato transplants, commercial tomato plantings and home gardens in potato late blight epidemics. (ranked #2 in Tomatoes and Late Blight)

*Determine the importance of lesion type on the initiation and continuation of epidemics. This includes potential genotype differences in the lesion type, location on the plant (stem verses leaf), and the importance of latent infections. (ranked #3 in Epidemiology)

*Investigate long distance dispersal of sporangia, especially in how this influences regional epidemics. (note-very similar to 1 in this same topic area; ranked #4 in Epidemiology)

5---Tomatoes and Late Blight
*Develop coordinated potato and tomato late blight research. (ranked #1 in Tomatoes and Late Blight)

6---Traditional Host Plant Resistance
*Develop collaborative plant breeder and plant pathologist efforts in establishing durable late blight resistance in commercial varieties. (#1 in Traditional Host Plant Resistance)

*Use cultivars with commercially acceptable processing and storage characteristics and moderate late blight resistance in concert with chemical and cultural tactics (IPM). (#2 in Traditional Host Plant Resistance)

*Intensify selection of germplasm with both foliar and tuber resistance. (#3 in Traditional Host Plant Resistance)

*Develop and initiate standard, long-term (several years) international variety trials (multiple field test sites) using standardized evaluation methods. (#4 in Traditional Host Plant Resistance)

*Develop long-term late blight resistant cultivar breeding programs independent of other "breakthrough" events. (#5 in Traditional Host Plant Resistance)

7---Molecular Host Plant Resistance
*Establish through surveys a community database describing resistant cultivar genetics. (#1 in Molecular Host Plant Resistance)

*Secure molecular markers that "tag" (identify) loci of interest (AFLP/RAPD/RFLP). (#2 in Molecular Host Plant Resistance)

*Improve understanding of horizontal (multi-gene/field) resistance. (#3 in Molecular Host Plant Resistance)

*Pursue basic research of natural resistance potential amenable to molecular manipulation. (#4 in Molecular Host Plant Resistance)

8---Cultural Control
*Study environmental (fertility, irrigation, drainage, etc.) modification to mitigate late blight severity. (#3 in Cultural Control)

9---Disease Forecasting/ Fungicide Application Technology
*Forecasting models need baseline research to more accurately incorporate abiotic components such as monitoring at the microclimatic and macroclimatic levels, weather forecasts, environmental systems (i.e., irrigated, rainfed), fungicide efficacy and timing, fungicide resistance/sensitivity, fungicide weathering. (#1 in Disease Forecasting/Fungicide Application Technology)

*Determine the effect of microclimate (including spring weather and early season irrigation) on the establishment of primary field infections. (#2 in Epidemiology)

*Forecasting models need baseline research to more accurately incorporate the following biotic components: initial inoculum from various origins (seed, cull, volunteer, oospore), pathogen dispersal, host and pathogen genotype variability, host phenology. (#2 in Disease Forecasting/Fungicide Application Technology)

*Research ways to standardize population monitoring. (#4 in Biology)

*Develop forecasting systems that combine BLIGHTCAST and TOMCAST for fungicide scheduling similar to those in place in Mexico. (#4 in Tomatoes and Late Blight)

*Forecasting and surveys need to incorporate local, regional and national geospatial relationships and technology based upon Global Positioning System (GPS) and Geographical Information System (GIS) tools, in addition to standardized disease assessment methodology. (#4 in Disease Forecasting/Fungicide Application Technology)

*Forecasting needs access to and support from more comprehensive and timely environmental monitoring, weather forecasting and technology transfer networks at state, regional and national scales. (#5 in Disease Forecasting/Fungicide Application Technology)

10---Regulatory
*Develop techniques to quantify relationship between late blight levels in seed lots and subsequent potential levels of late blight in the field and associated tolerance dependent on environmental conditions in target area and end use (i.e., seed vs non-seed). (#1 in Regulatory)

*Establish national protocols based on statistically sound and feasible methods for inspecting and sampling potato seed crops and seed tubers for late blight prior to shipping. (#1 in Identification)

*Develop and implement a voluntary standardized National Late Blight Screening Program for seed growers. Research is needed to determine reliability, sample size, incubation period and conditions for such a program to be successful. (#3 in Regulatory)

*Each state, province or production area should develop its own regulatory plan that defines various tactics (i.e., mandatory use of certified seed, cull pile and volunteer management, garden and garden center regulations), kind and system of disclosure, notification and reporting, and action in infestation situations. (#6 in Regulatory)

11---Chemical Control
*Continue research, development and evaluation of section 18 products until full registration, especially of new products such as fluazinam, Quadris, IB 17022 and other new potential late blight suppressant compounds. (#1 in Chemical Control)

*Continue research on application technology, chemigation and application equipment for enhanced coverage, especially stem coverage. (#2 in Chemical Control)

*Fungicides need baseline research on effects, costs/benefits and risk assessment of varying fungicide rates, intervals, chemistry and application technology (method, equipment, water volume, air speed, nozzles) on the host, pathogen and environment. (#3 in Disease Forecasting/Fungicide Application Technology)

*Continue research on vine desiccants and fungicide tank mixtures. (#3 in Chemical Control)

*Continue post harvest treatment with chemicals for tuber blight control in storage and for seed piece protection. (#4 in Chemical Control)

12---Education and IPM
*Endorse IPM (integrated pest management) approach using all cost effective, socially acceptable and environmentally benign appropriate technology and tactics. (#1 in Education and IPM)

*Policy makers (Ag Canada/Mexico/USDA) develop and implement vision/goals incorporating existing education tools (bulletins/video/1-800 numbers/CD ROM) and other computer driven and traditional media. Target traditional and new audiences and stake holders. (#2 in Education and IPM)

*Develop and implement comprehensive educational programs specific to targeted group (growers, seed-potato inspectors, processors, etc) relevant to their unique goals. The group also recommended that USDA specifically provide funding for development and implementation of regional training and workshops. (#2 in Regulatory)

*Develop programs to train all crop management personnel (e.g., growers, field managers, inspectors, extension agents, etc.) on accurate diagnosis and detection of late blight in plant materials and tubers. (#2 in Identification)

*Promote the recognition of fungal signs (mycelium and spore forms), disease prevention or management based on accurate understanding of fungal biology and disease cycle, and use of standardized scientific terminology (or nomenclature) for genotypes and new strains of the pathogen. (#5 in Biology)

*Develop funding for late blight information transfer to potato and tomato clientele. (#5 in Tomatoes and Late Blight)

*Fund, organize and promote North American Potato Late Blight Workshop II for 1999. (#3 in Education and IPM)

*Develop potato late blight WWW site incorporating:

*interactive components with new information daily about weather, disease forecast/incidence and other time sensitive information

*chat room - for exchange of anecdotal information

*resource library (research, photos, videos etc.)

(#4 in Education and IPM)

*Recommend that the upcoming APS interactive North American Potato Late Blight Workshop continue through April and May 1997. (#5 in Education and IPM)