A report has it that bacterial wilt disease is a threat to potato production in the African continent.
Global average potato yield is around 21 tons per hectare, while some farmers in Europe and North America can harvest more than 40.
But farmers in sub-Saharan Africa produce an average of about 8 tons of potatoes per hectare; the principal cause of that gap is a disease.
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According to a survey of potato experts in 10 sub-Saharan African countries in 2018, the most serious threat to the region’s potato crop is bacterial wilt disease.
Bacterial wilt disease
Caused by the soil- and seed-borne bacteria Ralstonia solanacearum, bacterial wilt is responsible for an estimated USD 1 billion of economic loss globally each year, largely because of eradication measures and restrictions imposed on contaminated farmland.
“Bacterial wilt is a difficult disease to manage,” says Kalpana Sharma, a scientist with the International Potato Center (CIP) who has led studies of its prevalence in several African countries that confirmed its considerable spread.
Sharma notes that whereas potato farmers commonly control other diseases (such as late blight) by spraying fungicides on their fields, there is no comparable agrochemical option for bacterial wilt management.
To reduce yield loss from seed-borne diseases, the International Potato Center promotes the establishment of formal systems that produce and disseminate disease-free seed.
However, most African farmers plant potatoes they purchase from informal markets or save from their own harvests, which perpetuates low yields.
To help government authorities and seed potato producers keep infected potatoes out of the seed supply, CIP is promoting the use of a technology called loop-mediated isothermal amplification (LAMP) to detect latent Ralstonia infections.
LAMP uses specifically designed primers to quickly diagnose an array of pathogens that affect plants, animals, or people – from sweet potato viruses to COVID-19. And because the technology is field deployable, it increases the efficiency and accessibility of diagnostics.
“There is a lack of cost-effective, reliable, and fast tools for bacterial wilt diagnosis in the government agencies of most potato producing countries in sub-Saharan Africa,” says Sharma.
“And they also lack the capacity and training to use them.”
She explains that CIP has published a manual on using LAMP to detect bacterial wilt and begun training people in government and the private sector on how to test potatoes, plants, or soil for the bacteria using LAMP and other diagnostic tools.
She adds that CIP is promoting the use of LAMP by private companies, which can offer diagnostic services to the government, seed companies, and large-scale farmers.
“There is no silver bullet for bacterial wilt,” observes Sharma. “Controlling it requires integrated strategies.”
She explains that those strategies include assessing the bacteria’s presence in potato producing areas and genetic analysis to determine which strains are prevalent since some strains are more virulent than others.
Understanding the distribution of those strains can contribute to more effective investments in regional management of the disease, and can help potato breeders develop resistant or tolerant varieties.
According to Sharma, educating farmers and decision makers about threat severity and management options is vital.
While it may be impossible to eliminate the bacteria once it has infested a field, various on-farm practices (e.g., removing or burning infected plants, crop rotation) can reduce the disease’s destruction and the risk of spread.
CIP has produced brochures and a video to educate farmers about the disease and best management practices.
“Contagious Ralstonia strains are likely being disseminated and exchanged across East African borders within informal potato trade channels among those countries,” warns Sharma.
“In the absence of potato seed certification and regional quarantine measures, bacterial wilt will become an increasingly serious problem and threaten the region’s rapidly expanding potato industry.”
The solution, Sharma says, is an integrated seed health strategy that combines resistant varieties and pathogen-free seed to safeguard potato production and food security for millions of smallholder families.