Kenya has been flagged as the entry point for the Apple Snail pest which could halve wet-rice production in East and South Africa and increase pest control costs by US155 dollars per hectare in the next six years.
According to research done by CABI and the Kenya Plant Health Inspectorate Services (KEPHIS), little time is left to contain the cureless Apple Snail pest which was first recorded in Kenya in 2020 and already affects 80 per cent of the Mwea Irrigation Scheme in Kirinyaga County causing yield losses of up to 50 per cent. Ahero and West Kano (Kisumu County), Bura and Hola (Tana River County) irrigation schemes which share water with Mwea are most at risk of invasion. The researchers further pointed out that once the snail gets to the Ahero scheme which shares waters with Lake Victoria it can be rapidly spread into rice schemes in Uganda and Tanzania. Lake Victoria’s waters also empty into major river systems like the Nile. Its spread into this major waterway would be disastrous as it provides irrigation water for 11 African countries. Ethiopia, Mozambique, Malawi, and Madagascar are all wet rice producers and have a suitable environment for the snail and risk it being carried to their farms through floods which have doubled in Africa since 1990, and the use of tractors, tractor ploughs, and harvesters from Mwea.
In real shillings and cents, Tanzanian rice farmers are projected to lose 0.5 tonnes of their rice production valued at US$100,764,157 in ten years without controlling the snail. If they control the snail, they are projected to lose half as much in the best-case scenario. Ethiopian rice farmers for their part will lose US$568,086 in 10 years and a minimum of US$312,447. Uganda is projected to lose at least US$6,022,968 to the apple snail.
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CABI has advised countries and counties outside Kenya where the snail hasn’t arrived yet to carry out strict quarantine to avoid it entering their farms. These include carrying out training to build awareness amongst farmers on the apple snail, avoiding or inspecting for egg masses disinfecting farm tools, machinery, and planting material from Mwea, and using physical barriers to avoid entry of flooding water in their farms.
To a lesser degree, waterbirds can also assist in spreading the snail by eating it and passing their eggs through their digestive system and carrying eggs attached to their bodies.
According to Fernadis Makale CABI’s lead researcher for the study, most attempts at curbing the pest through management have been too laborious, expensive, or proven to not be ineffective.
“The best way to manage the invasive snail is to stop it before it gets to your country, county, or farm through early warning and preemptive planning,” he explained.
Francis Migwi who has been losing more rice every year due to the snail culminating in a 1.35-ton loss from an acre of rice last year, explained that no pesticide has worked with Apple Snails by only collecting them by hand and then letting them burn out in the sun proving the to be the only sure way of killing them.
“This costs us an extra Sh4,400 every season, a fraction of what it would have cost us to buy pesticides to get rid of them,” Migwi said.
When farmers hand-pick the snails, spray them with pesticides, and replant destroyed rice fields, losses were reduced by up to eight per cent. This was however estimated to cost farmers six to 11 per cent more.
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CABI recommends that farmers hand-pick the nails and crush the eggs or dunk them in water to get rid of them. Farmers are also advised to avoid ratoon rice–regrowing new rice from the stubble left after harvesting the main crop. Alternate wetting and drying rice paddies create shallow ponds in the fields where the snails go and they can be easily collected to be killed. Avoiding direct seeding and instead using transplanted rice prevents the snails from eating the soft and weak rice seedlings. Limiting water paddy levels to below two centimeters reduces the spread of the snail and conserves water. Removing silt in canals reduces the snail’s preferred egg-laying area and their numbers.