By Francis Ndungu

Blight has wiped out potato crops across Nyandarua this season as farmers have struggled to prevent it in plants already weakened by fusarium wilt.

Isaac Mwaura, a potato farmer in Nyandarua, lost almost everything this season to blight and fusarium wilt. He said the loss followed the disappearance of the mancozeb brands he was using, after he had already switched to it when chlorothalonil was banned.

“In the agrovet the mancozeb was a big challenge since it appeared almost disappeared after agriculture ministry announced it was reviewing it. That forced me to shift to Mistress fungicides, which I was advised was a cure of blight. I planted the potatoes normally and expected to harvest as normally, since the weather was much favorable this year,” he said.

“My potato looked so healthy at the start of the first two weeks which gave me more expectation, which failed at the end. I felt much disappointed,” he said.

“I planted my crops normally with NPK, mixed it with the soil, and germination percentage was wonderful after two weeks. I then did my first weeding in three weeks’ time after planting, which later I sprayed rabbit urine at the rate of 1:20 litres to speed on the growth of my potatoes,” he said.

Isaac switched to rabbit urine fertiliser last year after foliar fertiliser prices rose. “Last year I started urine farming and increased my production from 20 to 30 bags in ½ an acre land. That was after I gained the knowledge from a church member and I adopted the method to cut short the cost of buying the fertilizer,” he said.

“Initially I had 15 rabbits, which I fed plants from the farm, but later bought some others after learning it could be of great help. I demolished my structure and built other structures as per the advice given, which eased the collection of urine, where I started collecting almost 2–3 litres per day, which I used to put in an airtight gallon,” said Isaac. “Rabbit urine contained nitrogen which is highly needed during the growing period of the plants.”

However, despite his preparations, he could not control the diseases.

“Before, after first weeding 3–4 weeks after planting, I sprayed chlorothalonil, which prevented my potatoes from early blight, which started being exhibited by yellowing of the last leaves from the ground. But now it is banned. I had changed to mancozeb, but this year I went to the agrovet demanding the same but the fungicides was nowhere to be found. I could not believe on that. Later I went to Nyahururu town to confirm but it was nowhere to found. I was then recommended Mistress, which I used, but it did not work. The blight caused scorching of the potato’s leaves, which caused premature leaf fall, which led to low production. This was after I adopted Mistress, which failed to save me from blight tragedy,” said Isaac.

In fact, Mistress contains mancozeb as one of its two active ingredients. But the delay in spraying, as Isaac searched for products he recognised as mancozeb, meant it may have been applied too late to prevent the blight, which it cannot stop once started.

Mancozeb is also less well suited to Kenya than chlorothalonil. Chlorothalonil works at higher temperatures, up to 30 degrees Celsius, where mancozeb works well up to 24 degrees Celsius, with much of Kenya’s farming taking place at higher temperatures. Chlorothalonil also continues working through downpours in the long or short rains, but mancozeb cannot continue working through and after a heavy rainfall.

“Chlorothalonil worked excellently in control of blight challenges, but now am left stranded because I don’t know what to spray to work,” he said.

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The government has not given a reason for its ban on Chlorothalonil or the other pesticides it has banned, and farmers are reporting widespread frustration on the crop losses.

“Initially before any remedy for the blight, I could harvest less than 15 bags on ½ an acre, which later translated to over 25 bags on the same land after introduction of chlorothalonil against early and late blight,” said Isaac.

But this year, the combination of fusarium wilt, followed by blight, took out far more. “This year fusarium wilt started in 3 weeks after planting and had reduced my potatoes’ growth. With the blight as well I lost up to 80% after the death of the whole plants. The fungal disease started with the wilting and yellowing of lower leaves, which progressed upwards, leaving the whole plants dead,” he said.

“I normally fumigate my soils to keep off the soilborne diseases, which majorly left other farmers who ignored it to suffer. Other years I have been controlling the soilborne diseases like fusarium wilt, phytophthora, which attack our crops in case they are not controlled,” said Isaac.

However, this season, even the remaining healthy plants were hit. “80% of the potatoes remained, which later got finished as a result of blight, others getting stunted growth due fusarium wilt,” he said.

“Initially I thought I was the only one who suffered from low production, but later had heard other farmers complaining about the same after church services and during farm meeting, raising the same concern of blight and fusarium wilt,” he said.

“I went to the agrovet to check for fungicides which could suit my potato but sold many varieties which did not work, but instead increased loss on my side. I gave up on my potatoes, which rotted and thus not conducive for consumption nor for planting,” he said.

Isaac later called an agronomist, who told him to stop planting potatoes for 2–3 years and to remove any growing potato plants.

“I was advised to uproot and destroy the growing potatoes in my farm, which he said was the carrier of the soil borne disease. I did uproot soon after the seed germinated, before the plant formed the tubers. The uprooting involved the removal of the whole plant together with the tuber,” said Isaac.

“I was told to plant maize instead of potatoes, which I felt it’s not right because I did not have large piece of land to practice maize farming. Again the climatical conditions in my area do not support the growth of the same due to extreme temperatures, which hastens their growth and prolong the maturation period, thus hard to make profit as experienced in potato farming there before,” he said.

The agronomist also urged Isaac to stop using recycled seed. “In most cases I recycle planting material or buy from other farmers, which sometimes spread disease to my farm.”. But even solving the fusarium wilt would not prevent his biggest problem with blight, he said.