• Kenya is the leading producer of avocadoes in Africa, but disease puts yield at risk
• Researchers are fighting the disease through Trichoderma, a soil-based fungus
Image: MINISTRY OF AGRICULTURE AND LIVESTOCK DEVELOPMENT
Researchers have developed a biological control to manage a devastating avocado disease.
Phytophthora root rot disease is the most destructive disease in avocadoes, killing most trees in an orchard, and the young plants die immediately after infection.
The Kenya Agricultural Livestock and Research Organisation is fighting it through Trichoderma, a soil-based fungus, as well as capacity-building farmers.
“Kenya is gravitating towards biological systems where a farmer can actually produce biological controls to manage the diseases,” Kalro crop systems director Dr Lusike Wasilwa said.
She spoke during an interview with the Star at Kalro headquarters in Nairobi.
The phytophthora root rot was initially a minor pest, but now it’s moving towards a major disease, Wasilwa said.
She said the government is on alert and is taking measures to prevent the disease through the 10-year KAISP project, which is getting support from the New Zealand Institute and Food Research Limited.
Kalro senior research officer Dr Ruth Amata said the disease kills the roots of avocado trees, and it is devastating.
“This is the most serious disease of avocado worldwide. It kills trees at any age and can seriously affect new plantings or seedlings with the progressive loss of trees making orchards uneconomic,” she said.
The researcher explained that root rot is the pathogen, which is the agent that kills the roots and eats into the roots.
Symptoms of the disease includes yellowing of leaves that later fall off, and eventually the entire avocado tree dries up.
The disease is a limiting factor in avocado production and this is a threat to the country's avocado export market to various destinations, including China.
In Kenya, avocado is the fourth-most important fruit after banana, pineapple and mango.
According to the Fresh Produce Consortium Kenya, Kenya is ranked 6th in the export of avocados globally, and 1st in Africa.
In addition, Kenya is ranked 3rd after Israel and Mexico among avocado exporters to the European market, with Netherlands, UAE, France, UK and Saudi Arabia being the fifth largest importers of Kenyan avocados.
The country has a huge potential in farming and exporting avocados and bananas, according to the consortium.
But scientists say this can be jeopardised by the Phytophthora root rot disease.
Amata said they have been training farmers through building their capacity on the disease so that they may be aware and be able to pick out the symptoms of this disease before they even start an avocado orchard.
“Any tools that the farmer uses can be able to spread the disease. Shoes, boots, vehicles moving within an infected field, through water and also heavy rains can be able to move the soil from the infected area to a non-infected area,” Amata said.
She said farmers should ensure they buy their seedlings from reputable, reliable nurseries that observe high levels of hygiene.
“The disease is soil borne and comes with the seedling right from the beginning when farmers are starting their orchards,” she said.
“They need, therefore, to start off with seedlings that are Phytophthora-free, and this can only be done if they source their seeds from reliable dealers.”
Amata said Kalro produces disease-free quality seedlings, which farmers can access from Kalro centres and Mkulima shops at places including Thika, Kabete and Muguga.
Dr Bob Fullerton from the New Zealand Institute for Planet Food Research said if a farm is contaminated with the Phytophthora root rot disease, it would be very hard to get rid of it.
Spraying can take as long as five years before the risk goes down, he said.
“It is hard to get rid of the disease once it's on either the ornamentals, weeds and also the plants,” he said.
“It will never go away and that is why particularly for the developed country, it is important to ensure you get seeds that are disease-free and from recommended nurseries.”
Fullerton, the principal investigator of the project, said they have introduced testing services to detect the pests through a partnership with Kalro.
He said they have also been working towards developing and introducing new and improved technologies to support the growth of avocado industry in Kenya and also ensure a sustainable future for the industry.