A portable decision support tool cuts fungicide use in Kenya, keeping potato harvests and environmental health high

Late blight presents a double-edged challenge for potato farmers in Sub-Saharan Africa: not only does it cause significant yield losses and production costs but it also poses health and environmental risks. Picture this: in peak rainy seasons, farmers in Kenya, a typical scenario in Sub-Saharan Africa, spray fungicides as frequently as 14 times a season-essentially 2-3 times a week. Now, think about the labor, time and financial burden, and the chemicals seeping into the environment, potentially affecting animal, aquatic and human health. 

To tackle this challenge, CIP introduced a simple yet effective solution: a decision support tool (DST) crafted from simple card paper to assist farmers in their spraying decisions. This tool is a game-changer, requiring basic record-keeping, like noting past rainfall days and the days since the last spray. And for those who prefer smartphones, a user-friendly Android version is available, making tracking and managing spray records even more effortless. 

So, how does this tool work?  

The DST helps farmers tackle three crucial questions: 

  1. When should I apply fungicide? 
  1. Which fungicide is best at this time? 
  1. How frequently should I use it? 

Using the DST is simple: pick the color disc for your potato variety—red for susceptible, yellow for moderately tolerant, and green for highly tolerant. Then, check if there’s been any rain since your last spray, and note the frequency and the days since your last fungicide application. The DST gives you a customized recommendation by adding up the corresponding numbers on the disc.  

Photo 1: Decision Support Tool for Potato Late Blight Management: Red for Susceptible, Yellow for Moderately Tolerant, and Green for Highly Tolerant Varieties” – Photo credit: CIP

And does it make a difference? Absolutely! Field trials in Kenya, with 71 farmers directly involved, revealed a substantial decrease in fungicide sprays per season with the DST. Number of sprayings dropped by half, from 12 to 6. This cut the environmental impact in half (from 345 to 183 EIQ/Ha) while maintaining harvest yields as bountiful. It’s like cutting in half the harmful chemicals that used to seep into the soil, polluting water bodies, and possibly entering our bodies, all while keeping yields steady or even better. In addition, a reduction in the number of sprayings means a reduction in the fungicide cost, labour cost and time, thus contributing to overall net returns on investment.  

In addition, the DST empowers farmers to explore alternative fungicides with lower environmental footprints. Florence, an extension agent in Kenya, emphasized this, saying, “My farmers never considered fungicide alternation as a strategy to enhance efficacy, but with the guidance from the disc, it’s proving to be remarkably effective. 

You might wonder, “But won’t alternative fungicides cost more?” Well, yes, some fungicides may come at a higher cost. However, as Maina, a farmer in Kenya, observed, ‘By alternating chemicals, I achieved healthier crops with higher yields compared to my conventional method that relied solely on mancozeb, thus recovering my costs, and attaining greater returns. Plus, this resulted in a reduced harmful impact on nature—a win-win! 

Moreover, the DST isn’t just about recommendations; it’s also about tailored education. It teaches farmers to keep good records, so they know exactly what and when to spray. This helps prevent wasting chemicals and keeps the environment safer. And here’s the kicker: During periods of low disease risk conditions, characterized by low rainfall and low to moderate humidity, the DST often recommends farmers either not to spray or to apply contact fungicides- the latter are generally cheaper and environmentally friendly. 

Again, with DST, you can remotely make decisions. As one farmer observed, “With the tool, I don’t need to be tethered to the farm at all times. Armed with information about rainfall events and my last spray date, I can instruct my farm operator back home to take immediate action.” 

But does the choice of potato variety matter? Although the DST operates irrespective of the variety’s disease tolerance, integrating it with disease-tolerant varieties enables farmers to reduce fungicide application substantially, thus saving the environment with a similar magnitude. A Kenyan farmer shared, ‘I never anticipated that certain varieties like Sherekea would require so few sprays, only 6 compared to 11 for Shangi (the conventional variety). With the DST, it’s just four sprays for Sherekea and seven for Shangi, and the season is covered. However, with both practices, crop health and yield remain the same.  

Figure 2 compares (a) Unica and (b) Sherekea varieties against the conventional Shangi variety under Farmer Practice and DST Spray Regimes. – Photo credit: CIP

DST isn’t just a card-paper tool—it’s a game-changer for potato farming. Farmers can protect their potato crops, save money, and keep the environment healthy by making smarter decisions about fungicide choices and the number of spraying regimes. So, when you’re out in the fields next time, think about the impact of your decisions. With the DST by your side, you’re not just farming for today—you’re cultivating a healthier, more sustainable tomorrow for us all.