Late blight is the most serious disease to affect potatoes, and costs the farming industry worldwide a staggering €4 billion per year in crop losses and treatments. However, protecting potatoes against the disease caused by the pseudo-fungus Phytophthora infestans is becoming more efficient and sophisticated thanks to the use of Decision Support Systems (DSS).
DSS help farmers and their advisers make good crop protection decisions and in the case of late blight are weather-based due to the fact that disease outbreaks are closely linked to temperature and humidity. Now a new ENDURE-backed web tool is making it possible to test and compare some of the most commonly used DSS across Europe.
Having an effective DSS can be particularly important for optimum protection of the potato crop when it matters most AND for reducing fungicide use against diseases such as late blight as it allows farmers to break away from a standard spray programme - which may be weekly or even more frequent - and to treat the crop only when needed to maintain good control of the disease.
The team behind the EuroBlight network, with support from ENDURE, have created a freely available platform that allows any researcher (or anyone with an interest in this disease or DSS more generally) to test and compare weather-based disease models. Go to www.euroblight.net to test it out for yourself.
In this example, we can see how Smith Criteria and ProPhy predict late blight pressure at Marham, UK, in 2008. Click here to test EuroBlight for yourself.
The researchers created the new platform with the knowledge that weather-based ‘sub-models’ are key components in many DSS aimed at controlling pests and diseases and minimising pesticide use. Furthermore, the evolving biology of pests and diseases in combination with changing climates makes it necessary to continuously test and improve both existing and new weather-based models.
The platform, created by researchers from ENDURE partners Aarhus University, Denmark, and Wageningen University, The Netherlands, uses late blight as a model disease for demonstration purposes but the scientists say there is no reason why it cannot be developed for other pests and diseases.
The platform contains extensive weather data: hourly data from many European Union countries, both north and south, between 2006 and 2009. It also contains the following sub-models: PLANT-Plus disease risk (Netherlands), ProPhy disease pressure (Netherlands), Blight Management infection pressure (Denmark), Blight Watch Smith Criteria (UK), WURCP infection events (Netherlands) and Contact Fungicide degradation (Netherlands). The biological data available is taken from monitoring of both field experiments and potato fields around Europe.
So, given the fact we have all this data available what can we do with it? First, it allows any user to compare for themselves the DSS currently available. An interactive web page allows users to select the location, period of the year and the models for comparison (go to the Decision support section of the site to try it yourself).
For the researchers behind the platform, it has revealed that the results from different models for disease risk or infection risk give similar but by no means identical results. These differences must be analysed to improve crop protection strategies.
The next step for the researchers will be to use the data to test and compare the sub-models used in DSS in Europe against biological data from different regions. Future possibilities include developing this platform for other pathosystems and using the platform to analyse the impact of climate change on late blight control in Europe.
Many more sub-models will be added to the platform, says the team, and simple DSSs can be constructed using the models in the toolbox, which is aimed at integrating with and improving both existing and new DSS in Europe.
The site also contains details of 11 best practices identified by ENDURE’s potato case study team, describing how they are implemented in practice, barriers to their use, their contribution to reducing inputs and whether they can be used in organic farming systems. The best practice section also offers access to ENDURE’s four potato case study leaflets, which are the most popular publications produced by the Network.
Trials highlight progress
The important role DSS can play in reducing pesticide use against late blight is currently being tested by researchers at both Aarhus and Wageningen.
At Aarhus University’s Flakkebjerg research centre, Bent Nielsen and his team have been performing a field trial aimed at evaluating the optimal fungicide dose while providing high levels of disease control and good economy for farmers.
The idea behind the trial is to alternate two effective fungicides (in this case Revus and Ranman) and to adjust the dose according to the late blight infection pressure. The Dose Model used takes into account the infection level (including a two-day prognosis ), the status of late blight in the area (the closer late blight appears the higher the protection level) and the level of resistance in the potato variety.
In this year’s field trial researchers reported a 92% control of late blight using the Dose Model with only 57% of the fungicide used when compared to the full dose strategy (this was measured using the treatment frequency index, a more sophisticated way of measuring pesticide use which takes into account the amount of active ingredient used). This field trial is part of a programme to reduce fungicide use in potatoes being run in co-operation between Aarhus University and the Danish Agricultural Advisory Service.
Similar work is also being conducted in The Netherlands. Huub Schepers, who led ENDURE’s potato case study team, reports on the EuroBlight site on a trial run this year on a demonstration field in Colijnsplaat.
Here four strategies were used:
The question of whether to recommend lower dose rates in The Netherlands is now being investigated, but Huub notes, blight was fully controlled in all four strategies.
Further work in the Netherlands has been conducted by Geert Kessel and his team as part of the country’s Umbrellaplan Phytophthora, which has seen researchers develop more sophisticated strategies for protection programmes.
This means that instead of adopting a strategy based on weekly spray schedules or spraying when the previous application has degraded or is insufficient because of new growth (both are common strategies in Europe), the team is moving further.
A slightly more sophisticated version of these strategies uses a DSS to predict infection events based on weather forecasts and, while this alone can significantly reduce fungicide inputs while providing high levels of disease control, researchers reduced the default dose rate of the protectant Shirlan to 100%, 50% or 25% on susceptible (S), intermediately resistant (MR) and highly resistant (HR) cultivars. Last but not least, three 'add on' strategies were investigated (these have to be fulfilled in addition to a predicted infection event before a spray is applied).
The complete set of strategies 1-5 was tested on three cultivars (S, MR and HR):
Strategies 1 to 5 were tested in field experiments at Valthermond, which is located in the heart of the Dutch starch potato industry and known for its aggressive late blight population between 2006 and this year, and on potato varieties with varied levels of resistance to blight.
In general, says Geert, using more advanced spray decision rules can significantly reduce fungicide inputs while maintaining an excellent level of control. The choice of cultivar and the control strategy are the most influential factors, with the most sophisticated control strategies reducing the fungicide input to a minimum of 20% on highly resistant cultivars and to 50% on susceptible cultivars. In fact, using any control strategy rather than a weekly spray programme improves the quality of disease control and reduces the number of sprays.
For more information
If you found this article interesting, you might find the following useful:
ENDURE's potato case study leaflets (From Science to Field):
From the archives: Potato late blight: a €4 billion problem
To visit the EuroBlight website: www.euroblight.net
Last update: 24/05/2023 - ENDURE © 2009 - Contact ENDURE - Disclaimer