About
the Author
Mary L. Powelson received her Ph.D. from Oregon State University in 1973 and is currently Professor of Plant Pathology in the Department of Botany and Plant Pathology at Oregon State University. Powelson has worked extensively with soilborne diseases of potato and the cultural aspects affecting early dying, irrigation management, and its effect on Verticillium dahliae interactions on potato. She has taken an active leadership role in development of potato IPM systems and tactics. Powelson's present research is in the area of integration of cultural tactics to control single and multiple pests and diseases of potatoes and vegetables, emphasizing effects of water-deficit stress on vascular wilt diseases, integration of reduced rates of soil fumigants, plow-down of green manure, and management of irrigation water to suppress root and foliar pathogens. Powelson, along with D.A. Inglis (Washington State University), has received support to develop a late blight web page and fungicide evaluation program.
Integrated
Pest Management/Education Programs
for Late Blight of Potatoes
Mary L. Powelson
Oregon State University
In recent years late blight, caused by Phytophthora infestans, has become a key disease in most potato producing regions of North America. Because this disease has caused significant economic damage, requires a relative amount of management (particularly chemical) and some form of alternative management techniques are available, a proactive IPM program for late blight is becoming a reality.
The fundamental concepts underlying effective IPM programs were summarized well by Dover in 1985 (2) and are applicable today for late blight: 1) optimization of disease control in an ecologically and economically sound manner; 2) emphasis on coordinating use of multiple tactics to enhance stable potato production; and 3) maintenance of disease damage below injurious levels while minimizing hazards to humans, animals, plants and the environment.
Applying IPM to late blight has consisted of using cultural management components and making foliar fungicide timing and application more efficient. Therefore, if the major goals of a late blight IPM program are product quality, environmental stewardship and producer profitability, measures that PREVENT disease such as destruction of sources of initial inoculum (cull piles and volunteer potatoes), planting of clean seed, and the timely application of efficacious and cost effective foliar fungicides will prove most beneficial.
Nearly all inoculum responsible for initiation of foliar infections originates from infected tubers. Because clean seed is an essential component of an IPM program the potato industry must resolve the political problems associated with this aspect, then implement appropriate technology to minimize contamination of seedlots. Recommendations to 1) destroy cull piles that originate from sorting into and out of storage, seed cutting and planting, transloading, and removing dirt and debris from storages, 2) manage volunteer potatoes, and 3) dispose of known infected seedlots are stressed in most outreach programs (5,6). Nevertheless, these recommendations are not readily accepted by the industry. A risk assessment of these inoculum sources is needed for a cost-benefit analysis.
Awareness of disease potential and status within both the production area and individual plantings is essential if timely applications of fungicides are to be made. Weekly scouting visits to individual fields and prompt notification of disease presence to both the grower and extension personnel allows the industry to take action in a timely and efficient manner. In addition to scouting, disease forecast models have been developed (3,4) and these predictive systems have been computerized. In many areas information on the current status of disease and on occurrence of favorable environmental conditions for infection is available through 800 numbers and WEB sites.
One of the major benefits of accurate disease forecasts and early detection of disease is the timely application of efficacious materials. For many years contact fungicides and in some instances systemic fungicides (metalaxyl) have been used to manage this disease. Recently strains of the late blight pathogen have developed resistance to metalaxyl (1) and some of the strains are regarded as more aggressive than strains known previously. EPA approved Section 18 Emergency requests from many states in 1995 and 1996 for use of three new chemistries (cymoxanil, dimethomorph, and propamocarb). These new materials have both protectant and limited systemic activity and are more expensive than most of the currently registered protectant fungicides. In 1996, seven defined protectant fungicide spray programs involving both registered and Section 18 chemicals were evaluated against late blight of potato under a wide range of environments, disease pressure, and host susceptibly so that efficacy of these programs could be compared. Results on fungicide program efficacy and an economic cost-benefit analysis of treatment programs have been distributed to extension and chemical industry representations for use in outreach programs. In the near future, these results will be available via a WEB site.
Technology has transformed the way we live and work. This transformation has also revolutionized the ways researchers and extension specialists teach and the ways producers learn. Many of these new technologies are currently being used in education programs on management of late blight. Nevertheless, several broad areas in technology transfer and education needs have been identified that can enhance the effectiveness of late blight IPM; e.g. 1) enhancement of computer databases, knowledge based systems, and networks that provide state of the art information; 2) production and electronic distribution of up-to-date educational materials; 3) stakeholder education of IPM strategies; and 4) a resource library of data on disease management strategies, photographs of disease symptoms, etc. available on a Web site that can be used in education programs.
The perception exists that the gap between the research and extension community and its stakeholders (potato grower and processor) is large. For IPM to be successful in management of this potentially destructive disease, the need for better communication and meaningful participation by all are essential.
Literature Cited
1. Deahl, K.L., Demuth, S.P., Sinden, S.L., and Rivera-Pena, A. 1995. Identification of mating types and metalaxyl resistance in North American populations of Phytophthora infestans. Am. Potato J. 72-35-49.
2. Dover, M.J. 1985. A better mousetrap: Improving pest management for agriculture. Study 4. World Resource Institute, Washington, D.C. pp 1-80.
3. Johnson, D.A., Alldredge, J.R. and Vakoch, D.L. 1996. Potato late blight forecasting models for the semiarid environment of south-central Washington. Phytopathology 86:480-484.
4. Krause, R.A., Massie, L.B. and Hyre, R.A. 1975. BLIGHTCAST: A computerized forecast of potato late blight. Plant Dis. Rep. 64:165-167.
5. Powelson, M. L. et. al 1996. Blight: The '96 strategy - a 4 Star Program to manage late blight. Spudman 34:13, 23.
6. Secor, G. A., Gudmestad, N. E., and Rodriquez. 1995. Late blight management. Valley Potato Grower Oct. 95.
MANEJO INTEGRADO DE PESTES/PROGRAMAS DE EDUCACION PARA TIZON TARDIO
MARY L. POWELSON
En anos recientes tizon tardio, causado por Phytophthora infestans, se ha convertido en una enfermedad clave en la mayoria de regiones productoras de papa en Norte America. Debido a que esta enfermedad ha estado causando danos economicos significativos, requiere de un cierto grado de manejo (particularmente quimico) y de algunas tecnicas de manejo alternativo que estan disponibles, un programa proactivo para tizon tardio se esta haciendo una realidad.
Los conceptos fundamentales que subrayan la efectividad de los programas de IPM fueron resumidos muy bien por Dover en 1985 y que todavia son aplicables hoy en dia para tizon tardio: 1) Optimizacion del control de la enfermedad en un sentido economico y ecologico; 2) Emfasis en el uso de tacticas multiples y coordinadas para incrementar una produccion estable de papa; y 3) mantener el dano de la enfermedad debajo de niveles no perjudiciales en tanto se minimicen los peligros a los humanos, animales plantas y al medio ambiente.
Aplicar IPM a tizon tardio consiste de un uso constante de manejo de componentes de practicas culturales y realizar aplicaciones de fungicidads foliares de forma muy eficiente y bien distribuidos. Consecuentemente, si una de las mayores metas del IPM es de ayudar a los productores de papa en Norte America el de alcanzar un control de tizon tardio a niveles economicos aceptables, medidas de PREVENCION de la enfermedad tales como la destruccion de fuentes iniciales de inoculo (monton de papas descartadas y de papas voluntarias), sembrar con semilla sana, y la aplicacion de fungicidas foliares en epocas optimas beneficiara en el costo y la efectividad.
Casi todo el inoculo responsable para la iniciacion de una infeccion foliar se origina de tuberculos infectados. Debido a que la semilla sana es un componente esencial de un programa de IPM la industria de la papa debe resolver los problemas politicos asociados con estos aspectos, la immplementacion en forma apropiada de tecnologias para minimizar contaminacion de los lotes de semilla y disposiciones apropiadas sobre los lotes de semilla que se conocen estan infectadas.
Aunque las recomendaciones de manejo de estas fuentes son estresantes en la mayoria de los programas mas adelantados, tacticas que son amigables con el medio ambiente y economicamente posibles no han sido afinados.
Experimentos para examinar la eficacia de los fungicidas sistemicos de penetracion a traves de la pared celular como piesas de tratamiento a la semilla para control de esta enfermedad estan actualmente en camino y los metodos de manejo de montones de deshecho de papa estan siendo evaluados.
Conocimento del potencial de esta enfermedad y de su posicion dentro de un area y de sembradios individuales es esencial si las aplicaciones de fungicidas son realizados en un tiempo oportuno. Visitas semales de exploracion a los campos individuales y notificacion de la presencia de la enfermedad tanto a los agricultores como a los agentes de extencion permite a la industria tomar acciones en una epoca oportuna y de manera eficiente. En adicion a la exploracion modelos de prediccion de la enfermedad han estado siendo desarrollados y estos sistemas de prediccion han estado computarizados. En muchas areas de informacion sobre el estado actual de la enfermedad y sobre la presencia de condiciones favorables del medio ambiente para la ocurrencia de la infeccion, esta disponible a traves de 800 numeros del sistema WEB.
Uno de los mayores beneficios de una prediccion apropiada y una detecion temprana de la enfermedad es la epoca optima de aplicacion de materiales eficientes. Por muchos anos los fungicidas de contacto en alguna instancia fungicidas sistemicos (metalaxil) han estado siendo utilizados para manejar esta enfermedad. Recientemente biotipos del patogeno de tizon tardio han desarrollado resistencia a metalaxil y algunos de estos biotipos han conseguido ser mas agresivos que los biotipos previamente conocidos. En 1996 muchos programs de fungicidads fueron evaluados contra tizon tardio de la papa bajo un rango amplio de medio ambientes, presion de la enfermedad y hospederos suceptibles. Los ensayos del National Late Blight Fungicide fue disenado de manera que programas de aspersion de fungicidas protectivos, tanto de fungicidas de contacto como los fungicidas sistemicos de penetracion a traves de la pared celular podrian ser comparados en numerosas localidades contra esta enfermedad. Resultados de este estudio van ha ser distribuidos como un paquete de diapositivas y reportes escritos de los cooperadores seran diseminados via WEB.
Muchas areas extensas de transferencia de tecnologia y educacion son necesarios para ampliar IPM en tizon tardio de la papa
incluyen: 1) ampliacion de almacenamiento de datos en la computadora, un sistema basado en los conocimientos, y un sistema de informacion que provea una informacion estual de alta calidad; 2) produccion y distribucion de un moderno material educacional; y 3) educacion del beneficiario con las estrategias de IPM.
La percepcion es que existe una abertura muy grande entre las comunidades de investigacion y extension y su beneficiarios (productores de papa y procesadores). Para que IPM sea satisfactorio en el manejo de esta enfermedad potencialmente destructivo, es necesario una mejor comunicacion y una participacion immensa de grupos grandes de beneficiarios es esencial.
