Implementation of an early warning system for sustainable preventive management of Potato late blight

By: Dr. Ivette Acuña B.( iacuna@inia.cl) INIA, Chile

Background

The potato is of social, economic, and cultural importance in Latin America, being the basis of food and the basis of the crop’s biodiversity. Crop diseases are one of the major limiting factors in its production, especially nowadays due to climate variability. Therefore, having methodologies that allow us to carry out an intensive but sustainable production, allows us to ensure food for the population and at the same time preserve the environment and people’s health. Early warning systems are useful tools to achieve this goal.

Therefore, in 2017 we presented a proposal to FONTAGRO called Implementation of an early warning system for sustainable preventive management of potato late blight (Phytophthora infestans de Bary), as an adaptation measure against the variability of climate change in Latin America. This project was performed between 2018 to 2023.

Potato is a major crop in Latin America and is the main food in family farming. It is native to America, as is the causal agent of Late Blight, P. infestans. Late blight is considered a re-emerging disease in this crop due to pathogen variability and climate instability that favours its presence and dispersion, with a high incidence and severity. Farmers, therefore, use pesticides excessively and inappropriately, increasing the environmental impact and health risks to users.

Early Warning system project proposed the formation of a platform of specialists in potato late blight to develop and implement an early warning system as tool to support productive systems of family farming in participating countries, according to available technology, enabling reductions in losses caused by this disease.

The System uses weather data alongside disease epidemiological information to estimate optimal control times. Two systems were implemented, one based on real-time connected weather station network information (www.tizon.inia.cl and Phytoalert) and a manual system that uses local environmental condition observation (DSS-HH). Both systems enable farmers to make management decisions based on the information delivered, improving the efficiency of agrochemical use, increasing crop productivity and profitability. The beneficiaries were small farmers that used potato as a main crop.

Phytophthora infestans monitoring: P. infestans is a pathogen that presents a high genetic variability in its populations worldwide, which can be expressed as resistance to fungicides, greater aggressiveness or change in required thresholds. Therefore, it is essential to determine the predominant characteristics in each sector. In turn, this information serves to estimate the potential gene flow of this population to other territories. Given the above, monitoring was carried out in the sectors of influence in charge of the participating institutions by country. In vivo samples and FTA cards were used for this purpose. The characterization of genotypes was centralized and carried out at INTA Argentina, in the Biotechnology laboratory of the CICVyA Unit. A set of completely standardized microsatellite markers (SSR) was used to carry out these studies, according to the methodology proposed by the Euroblight Network Euroblight.net.  A map of P. infestans population status for Latin America was prepared with the information generated.

Partners

This work was performed by researchers and extensionist of INIA Chile, INTA Argentina, INIAP Ecuador e IDIAP Panamá with the support of the private sector and the finance of FONTAGRO ATN/RF 16678-RG (https://www.fontagro.org/new/proyectos/alerta-temprana-para-el-manejo-del-tizon-tardio-d/en). In addition, a collaboration from Brazil, Uruguay, Peru and Costa Rica was obtained in collecting isolates.

Results

Early warning system: Early warning models to detect the conditions for the development of the disease indicate when it is more opportune to apply chemical control, thus reducing the number of applications and production costs with a more sustainable management.

During the project, work was carried out in these countries and territories to validate the warning systems through experimental plots, combining chemical control strategies according to warning, varietal resistance and integrated management.

These models were already being used in different countries with relative success. Thus, in the southern zone of Chile the warning system available on the platform https://tizon.inia.cl was successfully implemented in the southern zone, but validation was still lacking in the Chiloe Island with farmers working with native potatoes and in production systems different from those used in other sectors (Acuña and Bravo, 2019). During the project, the results of late blight control for all seasons clearly show that applications according to the alerts provide very similar control to the fixed schedule, and both are better than the control at disease onset. Additionally, tuber yield is closely related to the level of late blight damage on the foliage. Thus, under the same condition, when the disease occurs, yield is lower, but there are no differences between the treatments applied with alert or fixed calendar. When comparing the number of applications, it was found that an average of 3.6 and 10 applications were made, respectively, for alert and fixed calendars, which is equivalent to a reduction of 65.6 %, obtaining very similar control and yield results.

In Argentina, the PhytoAlert system, also available for a few years, had been validated with commercial farmers near Balcarce, but not in the northern sector in Tucumán, with environmental conditions different from those previously evaluated. In this study, PhytoAlert DSS achieved the same level of late blight control as the Calendar Control, but with fewer fungicide applications during the crop cycle in all years evaluated and, therefore, in the amount of active ingredients applied per unit area. The percentage reduction in chemical applications ranged from 25 to 66.67%, depending on the disease pressure that occurred in each season. When analysing the Environmental Impact Quotient at the field rate or EIQ-FUR, PhytoAlert DSS showed reductions of 22.06 to 70% with no negative effect on yield. On average, the validation showed that PhytoAlert DSS reduced (across all campaigns and locations) the number of applications by 46.67%, achieved a higher economic savings of 54.43% and a reduction in environmental impact of 45.99%.

Also, in the Andean zone, the International Potato Center (CIP) had worked in Ecuador and Peru with a manual disc system (DSS-HH), which has been shown to work well in areas where there are no meteorological data or mass communication systems, but had not been validated by farmers directly in Ecuador (Pérez et al., 2020). During the project, the system was evaluated in farmers’ fields in different areas of the Ecuadorian Sierra. The results obtained indicate that the plots managed with alert had control of the disease with the same efficacy as the strategy applied by conventional farmers. Similarly, yield values were recorded, while the use of the alert generated a 36.6 % reduction in the number of fungicide applications to control late blight, a 48.2 % reduction in environmental impact and a 49.16 % reduction in the cost of fungicides, on average for all the plots evaluated.

At the same time, in Central America, there was very little information on the management of potato late blight, but with very predisposing environmental conditions for this disease, for which farmers applied many times in each production, over 20 sprays, so in Panama losses became very high, mainly due to use of susceptible varieties and lack of training of both advisors and farmers in control strategies. Therefore, given the favourable conditions for the disease and the pressure of the pathogen, the strategy in Panama was based on varietal resistance evaluation and warning systems. Thus, in the Granola variety (susceptible) and the use of the DSS-HH tool for the control of late blight, six applications were reduced (38 %); in IDIAP Roja 17 (moderately susceptible) the reduction was up to eight applications (50 %); and in the resistant clone 398017.53 (resistant) the reduction was 69.23 %. This was reflected in the reduction of costs, being vital the use of moderately resistant and resistant cultivars. In addition, the use of early warning significantly reduced EIQ values.

In general, in all the sectors evaluated, the results were successful, it was possible to validate the early warning systems for late blight in 4 countries: Chile, Argentina, Ecuador, and Panama. The use of a warning systems allowed to reduce the number of agrochemical applications, environmental impact quotient (EIQ) and fungicide cost by more than 53%, 56% and 60% in average, respectively, obtaining levels of damage and yields like those obtained when controlling with a fixed application calendar strategy. It should be noted that for these systems to be successful, it is necessary to implement integrated crop management in order to reduce inoculum pressure and the risk of infection. Thus, under very favourable conditions and using susceptible varieties, the disease still occurs; however, when using varieties with medium to low resistance, disease control using applications according to alert is optimal.

P. infestans monitoring: The pathogen sampling protocol with FTA cards was successfully adapted, resulting in a valuable tool for genetic studies of P. infestans populations in Latin America, where potato-producing areas are distributed over a wide territory. During the project, a total of 528 leaf samples with symptoms compatible with potato late blight were collected. Phenotypic characterization was carried out, finding isolates resistant to metalaxyl in some countries. Genotypic characterization was performed using the 12-marker SSR multiplex PCR reaction proposed by Li et al., 2013), proving to be appropriate for the analysis of P. infestans isolates from Latin America. To complement this study of the genetic diversity of the pathogen, a dataset of SSR profiles of isolates from Brazil, Uruguay and Costa Rica was included. As a result, P. infestans populations collected in Argentina, Chile, Panama, Uruguay and Brazil were classified as belonging to the clonal line EU_2_A1, by comparison of profiles with published databases of world populations and with those reported in the EuroBlight Network. The isolates of P. infestans from potato crops in Ecuador belong to the clonal lineage EC-1, where the population is composed of a high number of genotypes that exhibit a high similarity to each other. In the case of Panama and Costa Rica, a new amplification pattern was detected, so its genotype is still to be defined. It is important to notice that studying the populations together and not in isolation will allow us to know how the pathogen evolves and thus be able to work together on more efficient and sustainable disease mitigation strategies.

Dissemination of knowledge: During the project, training was strongly carried out with the entire production chain, with 44 workshops, 8 field days and seminars, 7 workshops for the analysis of results with beneficiaries and partners, an international symposium, two workshops for co-executors and partners, 4 meetings and workshops with the production chain and decision-makers, with the participation of 2761 people, of which 42 % were women. In addition, 13 informative publications and technical videos were produced, as well as a scientific publication and a web platform where project information is hosted.

Also, a baseline survey was carried out to determine the farmer’s reality about the control of this disease and a follow-up survey was conducted at the end of the project. Farmers at the beginning of the project were aware of the disease and identify it as the most important one, but they did not know its epidemiology or the factors that favour it. It should be noted that the main form of control of late blight was chemical control, of which there was no complete knowledge of strategies with products, nor how to apply them efficiently and safely. At the end of the project, progress was made in the understanding and acquisition of knowledge, especially in the proper use of fungicides, the use of alerts and personal protective equipment when applying agrochemicals. Thus, untimely (non-preventive) applications decreased in Chile from 55% to only 15%, in Ecuador to 5% and in Panama to 7%. In relation to the above, the farmers at the end of the project also incorporated IPM, i.e. they are using more than a single control measure, thus, in addition to the application of fungicides, the use of disease-free seed, good soil drainage, high hilling and the elimination of diseased tubers before storage are observed. In relation to the above, after the project, 70% to 100% of the beneficiaries in all countries were trained in GAP, safe use of agrochemicals and equipment calibration, so farmers understand the risk when applying a fungicide and the importance to use them in a safe way. The use of warning systems was highly encouraged, especially in countries where there was no management strategy. As a result, major changes in the use of warning systems were seen in Ecuador and Panama, where increases of 81% and 27%, respectively, were observed. However, it is important to consider that training is a continuous process in which advisors and the entire distribution chain must be involved. There are decisions or knowledge that are complex for the farmer, so he turns to the advisor, the input distributor or even the neighbour to clarify his doubts. Also, consider that, in small-scale agriculture, women play an important role in crop management, both as the basis of the family’s food supply and as part of the marketing of the family’s products and income.

Finally, the use of information based on early warnings helps farmers to carry out chemical control in a timely and efficient manner and only when necessary. Thus, this information, together with training in integrated management and good agricultural practices, promotes adaptation and mitigation of climate change for the sustainable intensification of potato production.

Impact of warning system validation in Latin America. it was possible to validate the early warning systems for late blight in 4 countries: Chile, Argentina, Ecuador, and Panama. The use of a warning systems allowed to reduce the number of agrochemical applications, environmental impact quotient (EIQ) and fungicide cost by more than 53%, 56% and 60% in average, respectively, in relation to traditional management.

 

Discriminant analysis of principal components (DAPC) using 12 microsatellite loci. This 3D scatter plot shows the first two principal components of the DAPC of the Phytophthora infestans genotypes found in Latin America in this study. The groups are shown with different colors according to the assigned genotype. Source: F. Lucas. INTA Argentina.

 

Potato chain actors were trained in workshops on best agricultural practices, integrated management, and use of early warnings, emphasizing the correct use of agrochemicals and timely applications, with a total participation of 2761 persons, where 42 % women. In general, women are responsible for the potato crop management and germplasm potato keepers.