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This map displays primary areas of potato cultivation, based on area and yield data by district (25 total, including those where no potato cultivation occurs) provided by B.R. Egusquiza: La Papa – Produccion, Transformacion, y Comercializacion (2000). Total area under cultivation was adjusted downward from 285,000 hectares reported by Equsquiza for 2000, to 243,000, the average of 2002 and 2003 as reported by FAO. Yield data by districts are as reported for 2000, although the overall Peruvian national average has risen slightly since then.

Some adjustment was made to assign dots, each representing 1,000 hectares, to areas where the altitude range corresponds to most potato cultivation, very roughly from 2,500 to 3,500 meters above sea level in mountainous areas. (A coastal crop is also grown at lower altitudes.) However, since districts can cover a wide diversity of altitudes, given Peru’s extremely complex topography, placement of dots does not always precisely correspond to the appropriate altitude at a given point.

 

For further information on Potato Production click here

 

 

Rancha of Potato (Phytophthora infestans) in Peru

Rolando Egúsquiza B. and Walter Apaza T.
Universidad Nacional Agraria, La Molina, Lima, Perú.
e-mail: pegusquiza(at)lamolina.edu.pe

Translated from Spanish. E.N Fernandez-Northcote (ed). 2002. Memorias del Taller Internacional Complementando la Resistencia al Tizón (Phytophthora infestans) en los Andes, Febrero 13–16, 2001, Cochabamba, Bolivia, GILB, Taller Latinoamérica 1. Centro Internacional de la Papa (CIP), Lima, Peru.

  

Incidence and losses

Due to the geographical location and the climatic conditions determined by the Andean mountains and the Humboldt Current, potatoes can be planted and harvested practically year round (Table 1). In production areas of differing proportions, potatoes are produced in three cycles or cropping seasons, depending on the altitude of the production region –the coast, the intermediate highlands and the highlands.

 

In Table 1 statistics are presented for the three regions where potatoes are produced in Peru (coastal, intermediate highland and highland) including rainfall, temperature and relative humidity (RH), which are related to incidence and losses due to Phytophthora infestans. In the coastal region with altitudes of 0– 500 masl (meters above sea level), rainfall is near zero while the RH is high; these climatic conditions favor blight when inoculum is present and in years and localities when RH remains above 95% for long periods. Bazán de Segura (1950) studied the climatic conditions in the central part of the coastal plain (department of Lima) when late blight was present and absent and was able to predict disease onset when the night-time RH was higher than 95% for two successive days. Thus, she indicated that if the nighttime RH was lower than 95% and the thermo-period wide, disease does not develop.

For the reasons given above, the weather in the coastal region does not usually favor the “explosive” development of P.infestans. Moreover, climatic conditions are rarely adverse in this region and farmers grow a variety of crops and have access to modern technical support. In this region potato cultivars with high potential yield and market demand are preferred, such as the cultivars Tomasa Condemayta and Canchán INIA.

Tomasa Condemayta is highly susceptible to late blight (in the coast 3 to 6 fungicide treatments are usually required). Farmers chose it because of its tolerance to the leafminer fly (Liriomyza huidobrensis), which is the most important pest in the Peruvian coast, and because it is preferred by the potato chip industry. Similarly, farmers prefer to plant the cultivar Canchán INIA, which is also susceptible to blight (usually needing 2 to 4 applications), but which has a shorter growing period (four months), and a high market acceptability due to its color (pink) and its dry matter content (22% to 24 %).

In the intermediate highlands (500–3000 masl) potatoes are grown on the western (Pacific maritime) and the eastern (Amazonian) slopes of the Andean mountains and in the low inter-Andean valleys. Potato cropping in this region is characterized by early planting dates. Potato fields must be irrigated because the early growth and developmental phases of the crop coincide with the absence of rainfall. Precipitation occurs later when the plants have entered the phase of maximum tuber growth or maturation. As a consequence, disease incidence and losses due to P.infestans are relatively low in these areas.

It should be noted that potatoes planted at the beginning of the rainy season at the lower elevations of the highlands, as well as on the western slopes of the Andes, are highly vulnerable to damage by P. infestans.

The highland production region (3000–4000 masl) consists of rain-fed farming areas, and is the country’s largest potato cultivation area. In this region, disease incidence and losses due to blight are basically determined by altitude. The disease is present and harmful in fields situated between 3000–3300 masl when rainfall is concentrated in the phenological stages of maximum tuber growth and maturation. In fields situated between 3300–3600 masl, disease incidence and losses due to blight occur when high rainfall and warm temperatures coincide; and the disease is practically inexistent in fields situated between 3600–4000 masl. In this last zone, blight has only caused losses in years affected by the El Niño – South Oscillation (ENSO) phenomenon (1983–84; 1997–98).

Given the heterogeneity of the agro-climatic conditions under which potatoes are cultivated, it is difficult to make a precise estimate of the scale of incidence and loss caused by blight. For this document, highly experienced specialists of the potato-producing regions of Peru gave their personal estimations of blight severity in various departments and of the area planted to potatoes where the blight incidences is very low, low (requiring 2–3 fungicide treatments), high (6–8 treatments) or very high (requiring more than 10 treatments), which are presented in Table 2.

As can be seen in Table 2, 42% of the potato production area in Peru is exposed to high or very high levels of disease pressure. In other words, slightly less than half of the area devoted to this valuable food crop requires no fewer than four fungicide treatments to attain an economically viable yield.

In a similar approach, the International Potato Center (CIP) has distributed a map of blight incidence in Peru taking into account the climatic conditions of the various districts where potatoes are grown. This map is an aid towards an initial generalized appreciation of the problem, but considering the high agroclimatic variability typical of the Andes it is evident that more precise information is required.

Fungicides

The fungicides registered in the National Service for Agricultural Health (SENASA, Servicio Nacional de Sanidad Agraria) for controlling P. infestans in Peru are shown in Tables 3 and 4. Fungicides that are specific for controlling P.infestans constitute an important group in the Peruvian fungicide market and account for approximately 23% of the total amount of fungicides sold.

 

 

 

The most used active ingredients in Peru are metalaxyl and cymoxanil, which can be bought in different mixtures. A range of fungicides with substantially different properties is employed in both the coast and the highlands.

Fungicide use in the coastal region: Depending on the year and the cultivar, an average of 1–2 applications of a protectant fungicide and 1–2 applications of systemics (systemic+protectant) are made in a low blight pressure year. In high blight pressure year, 1–2 treatments with a protectant and 2–4 treatments with systemics will be carried out. The most used systemics are metalaxyl and cymoxanil.

Fungicide use in the highlands: As in the coastal region, 1–2 treatments with protectant fungicides and 2–4 with systemics will be made in years and zones with low blight. In zones and years of high blight pressure the same quantities of protectant fungicides are applied, but the number of treatments with systemics is increased to 6–8 in the season. In general, cymoxanil is the most used systemic fungicide in these zones. Fungicides containing fentinacetate are only used in the highlands, especially in misty conditions. In the coastal region they are not used due to the risk of phytotoxicity.

The fungicide cymoxanil is used in areas of the highlands with high disease pressure, such as certain inter-Andean valleys and on the eastern slopes. In these areas farmers have stopped using metalaxyl. This situation is reflected in the comparison of sales of fungicides for 1992 and 1999 (Figure 1).

 

Timing of fungicide applications

In order of importance, farmers base the timing of application on the availability of economic resources, personal experience, and the presence and persistence of the disease.

·         Availability of economic resources: When the farmer is financially solvent he applies the first fungicide treatment before disease symptoms are visible on the plants, even when climatic conditions are not favorable to the development or spread of the pathogen. In this case, low rates of fungicides are employed as a preventive treatment, taking advantage of the occasion to apply the fungicide in a mixture with an insecticide or a foliar fertilizer. When money is not available, treatments are made after damage is visible. Most potato producers do not have the necessary financial resources and try to borrow money or to buy the fungicides on credit once the disease has appeared. In these cases, the first application is made once the fungicide is available to the farmer and the effectiveness of the control will depend on how long it takes him to obtain it.

·         Personal experience: In zones where the there is a permanent risk of late blight farmers develop their own criteria with respect to the timing of applications and, more importantly, as to the mode of fungicide use (single product, mixtures, etc). In zones where disease occurrence is occasional or rare, most farmers lack experience and request professional help from technical assistants, or turn to agrochemical sales companies for advice.

·         Presence and persistence of the disease: As mentioned above, the vast majority of potato farmers in Peru start applying fungicides after symptoms have appeared, that is when disease incidence is noticeable and has reached a stage where it could jeopardize production. The frequency at which subsequent treatments are made depends on the farmer’s financial resources, and this last factor also determines the type of fungicide used.

Depending on the stage of development of the crop, certain farmers will abandon the plot or harvest early when there is a lack of economic resources or where climatic conditions are particularly favorable to the disease.

Throughout most of the potato-producing area of Peru there is a lack of institutions or specialists

responsible for providing technical assistance services. These services are available in the departmental and provincial capitals, but only rarely or not at all in the districts, villages, hamlets and peasant communities. Projects run by non-governmental organizations (NGOs) do exist in other areas and supply technical assistance with the drawback that they are often limited to a geographical area and in time.

Adapting treatments to specific contexts

As stated in the preceding section, farmers’ judgments regarding the use of treatment adapted to specific contexts are strongly influenced by their level of training, and consequently only a small proportion of them are able to make informed decisions.

Fungicide treatments are adjusted to the level of resistance of the cultivars used, or according to the climatic conditions that prevail in the highland areas, but this is usually an instinctive rather than an informed decision based on an understanding of the disease.

The adoption of cultivars and their spatial management are more conscious decisions than the adaptation of chemical control of blight according to different levels of cultivar resistance or the suppression of disease progress the higher the altitude.

Examples of this are the popularity and spread of the cultivar Renacimiento between 1950 and 1970 and of Yungay from 1970 to 1990. Palomino and Otazú (1987) found that Yungay had an acceptable level of horizontal resistance to which they attributed its popularity in the central highlands of the country. However, the main reason why these cultivars were adopted by farmers was because of their production potential, which was the consequence of their field resistance to P. infestans.

Another example is that farmers choose to plant native cultivars at higher elevations (above 3500 masl) principally because they recognize the higher cold requirement of these cultivars and not because of their higher susceptibility to P. infestans.

It is our opinion that only in areas where disease incidence is high, and especially, very high (at low altitudes) farmers prefer to adopt cultivars with genetic resistance and are aware that susceptible cultivars need more fungicide treatments.

Adaptation to climatic conditions

A network of stations run by SENAMHI (Servicio Nacional de Meteorología e Hidrología, National

Meteorology and Hydrology Service) record weather data in Peru. Unfortunately, the number and

localization of these weather stations is not in proportion to the range of agro-ecological conditions in the country. In addition, as is the case for many other public services in Peru, the SENAMHI has neither the resources to disseminate its weather reports in a timely systematic manner, nor the specialized staff to offer a forecasting and disease warning service. Presently, weather information is not freely available, and administrative procedures are often required to obtain access to it.

The decision to adapt fungicide application according to climatic conditions is for the most part based on experience, especially in those zones where blight incidence is high or very high. Farmers recognize that “rainy nights followed by sunny days” signify late blight development, and based on this experience, start treating with fungicides. Surveys conducted by Ortiz and colleagues (1998) in zones of high disease incidence in northern Peru found that most farmers correctly identified the climatic conditions that favor the disease.

Fungicide resistance

In Peru, potato growers in zones with a very high incidence of P. infestans quickly realized that

treatments with metalaxyl were not controlling the disease adequately. Subsequently, a study of 75 isolates from Comas, Cusco and Puno made by Raymundo (1998) found 82.7% of them resistant to metalaxyl. When a further 287 isolates of P. infestans from central and southern Peru were characterized by Pérez and colleagues (1999) three lineages were identified, two of which were metalaxyl resistant.

Gamboa et al. (1999) complemented the earlier studies by characterizing 307 isolates, among which were some from northern Peru. Pérez et al. (2000) characterized 208 isolates from Cusco and Puno (southern Peru) and found that all the isolates from Cuzco and half of those from Puno were resistant to metalaxyl. Otazú (2000) evaluated the efficiency of ten fungicides in Huasahuasi, a potato producing zone with high blight incidence, and found that metalaxyl performed poorly. In laboratory tests he demonstrated that the pathogen was resistant to this active ingredient.

Integrated management

The integrated management of late blight is composed of genetic and agronomic components.

Genetic component

The use of cultivars with appropriate levels of genetic resistance to P.infestans is without doubt a very important component of integrated management of late blight. The levels of resistance of the cultivars in commercial use in Peru are indicated in Table 5.

As can be observed, the most cultivated potato cultivars in Peru are susceptible to late blight and are hence planted, or recommended for planting preferentially in zones where there is no disease, or where disease only appears occasionally.

Farmers appreciate resistant cultivars, but they possess certain “disadvantageous” characteristics that should be taken into consideration:

·         Canchán INIA: Released in 1990 as resistant; presently is susceptible.

·         Perricholi: Released in 1984, is maintaining its level of resistance in many regions, but up to 90– 100% of the foliage area can be damaged if chemical control is not used in zones of high disease pressure. It has low dry matter content.

·         Amarilis INIA: Released in 1993, has a good level of resistance, but has the commercial inconvenience of being susceptible to greening.

·         UNALM Muru: Is field resistant since 1980, but is late and susceptible to greening.

The importance of resistant cultivars has been demonstrated in several experiments. Bailón and Otazú (1987) found that the resistant cultivar Perricholi yielded 8.2 times more than the control Revolución without any chemical treatment, and 3.5 times more that Revolución using the best chemical control available. Similarly, Gastelo and Landeo (1999) found that in zones with high disease incidence, resistant cultivars required only three treatments to produce a profitable yield, compared with more than 8 chemical applications for susceptible cultivars.

 

Agronomic components

·         Management of seed-tubers: Selection, reselection, disinfection and adequate storage of seed tubers are recommendations that, among other benefits, constitute part of the late blight integrated management program.

Selection and reselection make it possible to identify, isolate and eliminate infected seed tubers; disinfection is another seed management practice that reduces or eliminates inoculum that could be present on the seed tubers; and finally, storing seed tubers under conditions of diffuse light and improved ventilation reduces the spread of the pathogen from tuber to tuber and, by promoting greening, reduces infection by P. infestans.

·         Fertilizer use: Appropriate dosage of the macro-elements NPK (nitrogen, phosphorus, potassium), is recommended. Excess nitrogen application is known to increase susceptibility to late blight, while an adequate balance with phosphate and potassium corrects the unfavorable effects of excess nitrogen.

·         Crop rotation: The establishment of crop rotation systems is recommended to reduce the inoculum from plant debris in the soil. Following the same argument all plant debris and infected tubers should be removed from the field. However, it should be noted that population density is high in Peru and land holdings are small, thus making rotation recommendations difficult to put into practice.

·         Timing of planting: Farmers, especially those in areas where disease incidence is high or very high, are encouraged, wherever possible, to avoid planting at times when the weather is favorable to the development of late blight.

Farmers on the eastern slopes of the Andes prefer to plant susceptible cultivars in the dry months; these early crops characteristically reach maturity or early maturity when the rains begin. The two drawbacks to this practice are that few farmers possess irrigation installations on their land and that these early planted plots are harvested under rainy conditions and the tubers are muddy, lowering their commercial quality.

·         Spacing: Planting with increased spacing between and within rows is recommended to improve ventilation between plants, increasing the evaporation of excess humidity in the air around the plants and in the soil. Farmers in areas of high disease incidence are accustomed to increasing the distance between plants principally to reduce competition and produce a higher proportion of large tubers.

Generally, the recommendation to increase planting distances to create conditions that are less favorable to disease development has the disadvantage that the plant population is reduced, which could signify a lower yield per unit area.

·         Hilling: Hilling up over the tubers is recommended to protect them from air-borne inoculum. In Peru the recommendations are to hill up twice, or to make high hills in areas of high rainfall and where there is a high incidence of insect attacks or late blight. The creation of high hills may be an unnecessary practice for tubers of cultivars whose aerial parts are susceptible, but whose tubers are resistant. Concerning this aspect, tuber resistance could be determined by suppressive biotic factors, whose presence has been demonstrated experimentally (Torres, 1994). This investigation should continue, given that these biotic factors could provide a new component for integrated management.

·         Timing of harvesting: Early harvesting before physiological maturity is recommended in crops damaged by P. infestans to avoid disease spread to the underground tuberization zone.

·         Post harvest: Recommendations are that careful selection procedures should be followed for harvested tubers, and more importantly, that tubers should be stored in conditions of low RH and adequate ventilation.

Literature cited

Bazán de Segura, C. 1950. Posibilidad de pronosticar la iniciación y progreso del hielo de la papa

(Phytophthora infestans). Centro Nac. Inv. Exp. Agr. La Molina. Bol. 39:1–12.

Bailón, Y.y Otazú, V. 1987. Aspectos económicos en el control de rancha (Phytophthora infestans) en dos zonas con diferentes niveles de incidencia. Fitopatología 22: 59–60.

EDIPRENSA. 2000. Vademécum Agrario. El Ingeniero Agrónomo. 3 era edición. Lima, Perú.

Gamboa, E.S., Pérez, W. y Nelson, R. 1999. Uso de marcadores moleculares en la caracterización de poblaciones de Phytophthora infestans en Perú. Fitopatología 34:188.

Gastelo B., M. and Landeo, J. 1999. Determination of the minimum number of contact fungicide

applications in varieties with horizontal resistance to late blight (Phytophthora infestans ). pp 117–118 in: Crissman, L. and Lizarraga, C. (eds.), Proceedings of the Global Initiative on Late Blight (GILB) Conference, Quito-Ecuador. Vol I. International Potato Center, Lima, Peru.

Ortiz, O., Winters, P.y Fano, H. 1998/1999. La percepción de los agricultores sobre el problema de tizón tardío o rancha (Phytophthora infestans) y su manejo: Estudio de casos en Cajamarca, Perú. Revista Latinoamericana de la Papa. 11:97–120.

Otazú, V. 2000. Orientación en el uso del control químico de Phytophthora infestans a los productores de semilla de papa de Huasahuasi-Perú. Pp. 51 en: Memorias XIX Congreso de la ALAP, Febrero 28 – Marzo 3, 2000. La Habana-Cuba.

Palomino, A.H. y Otazú, V. 1987. Tipos de resistencia a Phytophthora infestans en algunas variedades peruanas de papa. Fitopatología 22:56.

Pérez, W., Gamboa, S., Coca, M., Raymundo, R., Nelson, R. 1999. Characterization of Phytophthora infestans populations in Perú. pp. 127 in: Crissman, L. and Lizarraga, C. (eds.), Proceedings of the Global Initiative on Late Blight (GILB) Conference. Quito-Ecuador. Vol I. International Potato Center, Lima, Peru.

Pérez, W., Gamboa, S., Coca, M., Raymundo, R. y Nelson, R. 2000. Poblaciones de Phytophthora infestans en el sur del Perú. Fitopatología 35:21.

Raymundo, C.R. 1998. Estructura racial y reacción a metalaxil en poblaciones de Phytophthora infestans en cultivos de papa en Comas, Cuzco y Puno-Perú. Tesis Ing. Agr. UNC Huancayo-Perú.

SENASA. 2000. Compendio de plaguicidas agrícolas y sustancias afines registrados en el Servicio de Sanidad Agraria (SENASA). Ministerio de Agricultura, Lima-Perú.

Torres, L,J. 1994. Supresividad del suelo al ataque de Phytophthora infestans (Mont.) de Bary a

tubérculos de papa. pp. 16 en: VIII Congreso Internacional de Sistemas Agropecuarios Andinos. Valdivia-Chile.

 

Links to World Potato Atlas (WPA)

 

(English)

 
http://research.cip.cgiar.org/confluence/display/wpa/Peru

 

 

(Spanish)

http://research.cip.cgiar.org/confluence/pages/viewpage.action?pageId=13089