Written by Mercyline Tata

Late Blight Management in Developing Countries

Late blight diseases –caused by phytophthora infestans, remains one of the most destructive disease to potato farmers, costing them an estimated USD 3-10 billion per year globally. In Kenya where smallholder farmers grow potato, the disease can destroy as much as 70% of their crops. In developing countries, late blight is not being monitored correctly because little to no work on genotyping late blight has been done. New strain evolves that is resistant to fungicides.

In response, International Potato Center , one of the partners under Feed the Future Innovation Lab for Current and Emerging Threats to Crops , is working in Kenya and Honduras on potato late blight management to implement a new genotyping platform based on amplicon sequencing.

Two trials fields have been established at Njabini agricultural training center (ATC) in partnership with the county government of Nyandarua and the national potato council of Kenya. Nyandarua is a major potato producing zone in Kenya. 

“It’s an exciting opportunity to have these trials on our field. Back then, most households planted potato but due to climate change, stressors like late blight disease have caused low yields leading to low potato production in the county. Our research station is accessible to smallholder farmers who can visit and learn about the trials.” Says David Karimi Gichuki, Principal at Njabini ATC.

The trials are established to determine susceptibility and resistance of varieties grown. Four potato varieties have been planted.  Sherekea variety which is considered resistant, Unika variety which is considered to be moderately resistant, Shangi variety considered to be susceptible and Dutch Robin which is highly susceptible. After application of various treatments, a disease progress curve will tell which variety is most susceptible to late blight.

Additionally, CIP’s handheld decision support tool is being tested and validated.The tool is in form of a disk; a red disk is used for susceptible variety, yellow for moderately susceptible and green for resistant variety. The decision support tool is based on farmer's knowledge about the weather during the past seven days, when was the last time they applied the last control and susceptibility or resistant level of a variety. The decision support tool helps to inform the treatment.

 “Late blight is a big problem and farmers need to spray fungicides which often is not environmental friendly. Farmers are not usually aware that you can adjust your spray regime based on your crops as well as weather conditions. If a farmer grows a more resistant variety, they will spray much less. They can do that based on decision support tool with confidence. So they end up saving money, crops and the environment. It is a win - win for everybody.” Jan Kruz, expert from CIP expounds on the benefits of the handheld tool.
Shadrack Nyawade, an expert from CIP - Kenya adds, “Most farmers go the agrovet and they don’t know which fungicides to use. Improper use of fungicides lead to resistance of the disease. With this tool, it will tells a farmer when to apply a fungicide so that he/she apply moderately.  We are able to give the list of specific fungicide a farmer can rotate with. With that alternation, the resistant build up will be low."
In conclusion, data will be collected from the trials to parametrize crop model and late blight model that will be able to do predictions on the disease pressure, disease severity and how that affect yields based on weather conditions.




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