Farmers raise alarm on falling potato production

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For 40 years, Danson Gitau, a farmer in Kahuho village in Karati, Nyandarua County successfully produced potatoes and managed to get very good yields. Like many farmers in his village, potatoes have been his main source of income.

In the last five years, however, potato yields from his 4 acre farm have been so low that he is considering abandoning the crop for another option. “I have tried to increase the amount of fertilizer and even compost but the yields are still going down and there has not been any improvement. I know it is not the rains because we usually have good rains,” he says.

Declining yields

Gitau says that before the problem started about five years go, he could harvest up to 20 bags in a ¼ acre of land. But in the last few years since, his potatoes have been stunted, some with yellow or wilted leaves. Eventually the potatoes develop very small tubers or none at all. “I think there is some type of bacteria in the soil because the potatoes do not show signs of other diseases such as bacterial wilt, which we have managed to control before through crop rotation,” he adds. His neighbour, Mweha Githakwa has the same story. He used to grow 6 acres of potatoes which would give him between 60 and 80 bags of potatoes per acre. Now he can hardly harvest 20 bags in the same fields.

“Last season I got only 15 bags which I want to sell as seed. Potatoes have been our cash crop since Kenya’s independence. Now we do not know what to grow because the only other crop that does well here is cabbages whose price is very low in the market,” he adds. Joseph Mwangi, another farmer in the same village has also noted a drastic reduction in potato yields in the last five years. Before that, he says he could harvest as many as 40 bags an acre, but now he may harvest about 15 bags.

Comparison: Johnson Mwaura tends a healthy potato crop in August 2006 (Left). Mwaura works on the same potato plot last month (Right). Farmers in Nyandarua are baffled by declining potato yields.However, scientists have identified Potato Cyst Nematodes (PCN) in many farms in the area.

“People say it is climate change but even those using irrigation are complaining. I think there must be a problem in the soil which only the government can investigate and give us a solution. Otherwise it is just a waste of money to grow potatoes again,” he says. Samuel Mungara, a farmer in Passenga in Nyandarua County has had a similar experience with potatoes. “When I consider the losses I have incurred in potato production, I am really disappointed. I should have bought dairy cows and gone into dairy farming on a full time basis,” he laments.

Mungara says he has been growing potatoes for the last 8 years but the yields have been going down every year despite improved potato management. Joseph Mwaura, a farmer in Murungaru blames it on potato over-cultivation. He suggests that the problem could be ‛tired’ soil and advises farmers to come together and ask the government to test the soils, and advise on the type of fertilizers they should use. The same potato yield loss problems are narrated by many farmers in Ndaragwa, Njabini, Magumu, Munyaka Ndunyu Njeru, Engineer and Ol Kalou in central Kenya.

Potato pest a mystery

Potatoe production in the country is affected by diseases and pests. But farmers are usually able to control them through crop rotation and other good management practices. However, the current drop in potato yields in many farms has baffled them.

Researcher James Mwangi checks a potato plant for the PCN pest in Tumaini, Nyandarua County.

Two years ago, James Mwangi, a Kenyatta University student who was doing research on nematodes in Nyandarua County came across the Potato Cyst Nematode (PCN). TOF published an article on the invasion of the PCN pest in Kenya ( Investigations later revealed that scientists at the Kenya Plant Health Inspectorate Service (KEPHIS) and KARI (now KALRO) had established the presence of the pest in the country 11 years ago in Nyandarua and passed on the information to the government. However no serious action was taken to contain it. After the story of the PCN invasion was published last year, the government carried out a passive survey where it was established that the pest had spread to all potato growing areas. There is no evidence of government measures to contain the pest.

What is Potato Cyst Nematode (PCN)?

Nematodes are tiny, thin worms that live in the soil. They cannot be seen with the naked eye unless when placed against light. They are usually one millimeter in length and are cylindrical in nature (like an earthworm). The potato cyst nematode is indigenous to Peru, South America but it has spread to other parts of the world such as Europe where potatoes have been cultivated for thousands of years. In Europe PCN cannot spread because of strict quarantine measures that have confined it to particular regions. In Africa, PCN nematodes have been identified in Northern Africa countries such Morocco, Algeria, Tunisia, Libya and Egypt. It has also been identified in Sierra Leone in West Africa and South Africa.

How can farmers identify PCN?

It is not easy for farmers to identify Potato Cyst Nematodes in the potato farms. Potatoes infested by the nematode show similar symptoms as those affected by other pests and diseases such as stunted growth, yellow or wilted leaves. The potato tubers are very small, while others do not put in any tubers at all.

How can farmers control PCN?

At the moment, there is no known chemical or biological pesticide that can control PCN. In affected regions, the most effective method is to ensure that no potatoes from the affected areas are transported or sold in the market both as ware (commercial potatoes for the sale) or as seed. This restriction is called quarantine. Farmers in affected regions are not allowed to grow potatoes but are instead encouraged to grow other crops that are not in the potato family.

Other measures that farmers can take include:

• Using certified potato seed at all times.

• Using quality declared seed from known or certified potato seed producers.

• Avoiding seeds bought from other farmers or those from unknown sources.

• All farmers where the PCN is discovered should stop potato production for up to 7 years. The pest can remain in the soil for up to 30 years. However, land remaining free of potatoes or other crops in the potato family for 7 years has less infestation of PCN.

• Farmers are also encouraged to practice crop rotation at all times to help reduce the population of PCN in their farms.

• Affected land can also be left to remain fallow for 7 years (where possible – however this may not work for many small-holder farmers in Kenya because land sizes are very small since they need the land to grow other food crops).

• Resistant potato varieties can be developed - this requires many years of research to come up with such local varieties.

Potato imports to blame for pest

Kenya can only produce only 1 per cent of potato seed required in the country. As a result, foreign companies mainly from the Netherlands and other European countries have been involved in importation of whole potatoe tubers for the last 15 years against phytosanitary laws. Farmers have however rejected these varieties and prefer local varieties such as Shangi which has an 80 per cent demand.

Our investigations have established that the pest has now spread to all government basic seed production and multiplication sites. During the recent restructuring of KALRO, experienced scientists involved in potato seed production were transferred leaving the KALRO basic seed production unit at Tigoni understaffed and with little capacity to produce seed.

>>Tell us how useful this information is to your farming enterprise. Share your experience by email to [email protected] or leave a comment below this article


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