The locusts began crossing into Kenya around Dec. 28, initially destroying pastures in semi-arid counties mainly occupied by herder communities.

They have since spread to the counties of Garissa, Isiolo and Samburu to the south and west, Agriculture Minister Mwangi Kiunjuri said.

“We recognise that the pest invasion, and the potential to spread rapidly to other counties pose unprecedented threat to food security and livelihood in the country,” he said.

The Food and Agriculture Organisation (FAO) said in a Jan. 6 update that while swarms of locusts in Somalia are expected to mature and breed there this month, there is a low risk that those in Kenya would breed.

FAO said there is also a risk that swarms could move into Kenya’s neighbours Uganda and South Sudan.

Last month, the FAO said locusts had already destroyed over 70,000 hectares (175,000 acres) of farmland in Somalia and Ethiopia, also threatening food supplies in both countries in the worst locust invasion in 70 years.

Conflict and chaos in much of Somalia make spraying pesticide by airplane – which the FAO called the “ideal control measure” – impossible, the agency said last month. (Reporting by George Obulutsa; Additional reporting by Noor Ali in Isiolo and Giulia Paravicini in Addis Ababa Editing by Maggie Fick and Toby Chopra)