Invasive snail threatens rice fields - study

Rice farm in Mwea Tebere Irrigation Scheme, Kirinyaga county, June 6, 2021. [Mose Sammy, Standard]

A new study has revealed that the invasion of apple snails poses a threat to rice production and food security in the country.

The study, conducted by researchers from the Centre for Agriculture and Bioscience International (CABI), was published on Friday in the journal Pest Management Science.

It highlights the impact of the apple snail, an invasive species native to South America, within the Mwea Irrigation scheme, the country’s leading rice-producing scheme.

The study was carried out between November and December 2021 within the 8,903 ha under rice production within the scheme. It was found that the invasion of apple snails, which was first reported in the county in 2019, had reduced rice yields by up to 14 per cent and net rice income by up to 60 per cent.

Lead scientist Kate Constantine, a Project Scientist at CAB said that while rice farmers in Mwea face various challenges among them water shortages, rice blast attacks, high cost of input costs as well as low land productivity and a lack of resilient rice varieties, the entry of apple snail remains a challenge.

Rice farmers across the country face challenges including shortage of machinery, bird damage and poor infrastructure.

“The recent introduction of apple snail has added to these challenges, posing a serious threat to rice production in the region and potentially across Africa,” Constantine said.

But with the Ministry of Agriculture and Livestock Development’s prediction that rice consumption will reach 1,292,000 tons by 2030, the entry of the snail into Kenya, according to the researchers, could further spread to rice fields in neighbouring countries.

They say that in case the snails spread into the rice-production area of Ahero, at the edge of Lake Victoria, rice production in Tanzania and Uganda would be threatened, and from here, the inevitable further spread would occur.

“The negative impacts will only increase over time as apple snail continues to spread. It is a call for urgent action. There is a rapidly narrowing window of opportunity for potential containment, or possibly even eradication before apple snail becomes widespread in Kenya, and the only feasible option will become management, with its associated high economic, livelihood and environmental costs,” Mr Fernadis Makale, co-author of the report says.

Apple snails are a threat to an estimated 300,000 small-scale farmers across the country. [Mose Sammy, Standard]

Already, apple snails are a threat to an estimated 300,000 small-scale farmers across the country and now the scientists warn that the consequences could be disastrous if mitigation measures are not put in place.

Even with the report projecting that it could spread to other rice-growing areas, local researchers have confirmed the spread while warning that this could be devastating if not mitigated early.

John Kimani, a rice researcher from Kenya Agriculture and Livestock Research Organisation (Kalro), said that Kenya only produces 12.8 per cent of what we consume. Close to 88 per cent of the rice being consumed locally is imported.

Of the 910,000 metric tonnes consumed in the country, only 320,000 metric tonnes are produced locally.

The entry of apple snails, according to Mr Kimani, could further devastate local production of rice as the snails feed on young rice seedlings aged below 45 days. 

“The snail feeds on young seedlings and is a major threat to rice production in the country. Already, the snail has spread from Mwea to Bunyala. It is spread by machines like tractors that operate across rice fields located in different parts of the country,” Mr Kimani said.

The spread of the snails, he said, happens when tractors are not properly fumigated before they leave the farm. In such instances, the tractors leave the farms with mud that either carries eggs of young snails that will finally be deposited in the next destination farm.

At the moment, researchers are trying to manage the spread of the snail through collaborations with farmers in affected regions of Mwea and Bunyala. The most viable way employed is avoiding the flooding of rice paddies, a situation that creates a favourable environment for the breeding of the snails.

“Research has proved that rice production does not necessarily need flooded rice paddies. They only need moisture in the soil and we are advising farmers to avoid flooding their rice paddies. This way, the snails do not multiply,” he said.

He added that employing the tactics is also a move to avoid the use of chemicals which causes environmental and health hazards as the chemicals find their way into rivers and waterways.

“There is also a need for thorough fumigation and even inspection and regulation of these tractors and even lorries from affected areas to avoid the further spread of these snails into other farms,” he added.