Kenya Plant Health Inspectorate Service (KEPHIS) and stakeholders including the Kirinyaga county government are working round the clock to control the Golden apple snails. This invasive pest was first reported in February 2020, and has so far affected over 550 acres of rice in Mwea irrigation scheme, mainly in Ndekia and Tebere sections. It has also been noted to have a serious high risk of invading close to 1,500 acres of the bordering lower areas that receive water from upper units. The snails, considered as a major problem of rice, have been reported to cause up to 80% destruction of the newly transplanted rice.
Golden apple snails have muddy brown shells and golden pinkish or orange-yellow flesh. They are bigger and lighter in color compared to native snails. Its eggs are bright pink in color.
The snails have been observed in high populations especially in the canals and paddies. They have a high reproductive rate as evidenced by the many egg masses within the rice farms as well as on the edges along the canals. The snails are mainly spread through water canals and reported to cause damage on rice leading to a reduction in both rice and seed rice production. Golden apple snails spend most of their lives submerged in water or mud, emerging only to occasionally forage, mate and lay eggs. Even though they spend most of their lives in water, they still require to breathe and do this through extending specialized breathing tubes to the surface of the water.
When water is absent, they bury themselves in the mud and hibernate for up to six months and re-emerge once conditions become favorable.
Golden apple snails’ eggs are bright pink in color.
KEPHIS is working with stakeholders in the management of the snails that have the potential to create food insecurity in the country. The stakeholders include the Kirinyaga county government, Ministry of Agriculture, National Irrigation Authority, PCPB, KALRO, MIAD, NGAO, WARMA, NEMA, Department of Public Health, the Presidential Delivery Unit, CABI, ICIPE and the University of Nairobi; this forms the Multi-Institutional Technical Team (MITT).
Egg masses (pink in colour) are laid on vegetation above the waterline. Surveys have recorded numbers as high as 45,000 eggs in an area that is 5m2 (9,000 per m2). The very high multiplication rate indicates a potential for catastrophic damage to rice if left unmanaged.
KEPHIS and CABI have initiated the identification of the pest using morphological and molecular techniques to ensure accurate identification of the pest. This will help in ensuring that correct management is applied and in pest reporting.
Proposed Containment measures of Golden Apple Snails
1. Undertake training and awareness creation
The MITT will develop technical materials on this pest through literature review. The National Irrigation Authority with support of other county teams will undertake training and demonstrations on the management of the pest to farmers and stakeholders.
2.Prevent field entry using a mesh as physical barriers
Snails can invade fields from canals, rivers and reservoirs. Farmers are urged to place a barrier where water enters and exits the field. Place a wire/screen or mesh bag on the main irrigation water inlet and outlet to prevent snail entry and exit. The mesh to be used will be fabricated.
3. Handpick snails
Handpick snails and crush egg masses. This is best done in the morning and evening when snails are most active. Place bamboo stakes to provide sites for egg-laying that allows easy collection of snail eggs for destruction. One can also use attractants or plants that attract snails such as papaya and cassava leaves to make hand picking easier.
4. Community-based snail management
To best control the snail, communities should work together to reduce snail numbers in their area. Conduct mass snail and egg collection campaigns involving the whole community during land preparation, planting and crop establishment. Keep fields drained as much as possible during the vulnerable stages of the rice plant (below 30 days) or transplant 25−30 day old seedlings from low-density nursery beds.
5. Registration of Pesticide(s)
The Pest Control Products Board in collaboration with agrochemical industries and efficacy trials institutions are fast-tracking registration of safe products for use on the pest.
6. Introduce changes to the cropping system
The status of the current rice crop in the fields is at maximum tillering and harvesting is expected from the last week of November 2020. Farmers should be sensitized to avoid ratoon crop after harvesting to free fields to enable pesticide application to minimize the populations of this pest.
7. Change planting patterns
Transplanted rice is less vulnerable than direct seeded rice. Farmers are therefore encouraged to plant healthy and vigorous growing seedlings. Raise seedlings in low-density nursery beds, i.e. less than 100g seeds per m2 and delay transplanting (e.g transplant 25−30 day-old seedlings). To reduce missing hills from snail damage, multiple seedlings per hill can be planted.
8. Manage water in canals
Golden apple snails have difficulty moving in water which is less than 2 cm above the soil surface, therefore keep water level below 2cm during the vulnerable stages of the rice plant. Construct small canals or canalettes (e.g. 15−25 cm wide and 5 cm deep) after the final land preparation. Pull a sack containing a heavy object around the edges of rice paddies or at 10−15m intervals. Canalettes facilitate drainage and act as focal points for snails making manual collection or killing easier.
9. Desilting of canals
Desilting of canals will minimize the habitable areas where the snails are laying their eggs and this will enhance the reduction of the populations.
10. Emergency pesticide application
Watering of the fields to be withheld for some hours, then applied to trigger the snails to emerge and come into contact with the water containing the pesticide. This process is repeated for 3 to 4 rounds. This will be a blanket emergency application to all fields. The process will commence from the high-risk area.
11. Biological control
Some natural predators like Red ants feed on the snail eggs while ducks (and sometimes rats) will eat young snails. Domestic ducks can be put into fields during final land preparation or after crop establishment when plants are big enough (e.g., 30−35 DAT)
12. Use repellant plants
Place toxic plants such as tobacco leaves in strips across the field or in canalettes.
13. Identification of the pathway of entry
Undertake molecular analysis or studies to identify species of this snail
Snails are left exposed on the ground where it is hoped they will desiccate and die.
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