A feared crop pest which has wrought devastation in Africa is now quickly spreading in Asia, only six months after it was first seen in the continent.

The United Nations food and agriculture agency said Fall Armyworm has been confirmed in Bangladesh and Sri Lanka after being first detected in India in July.

Agricultural experts believe the pest which eats maize and other crops has also reached Nepal, Thailand and Myanmar, though there is no official confirmation.

The spread puts the caterpillars within easy reach of China, the world's second largest maize producer.

The moth pest, which devours crops during the caterpillar phase of its life, can spread at up to 60 miles a day. Maize is its preferred meal, but it can also eat rice, sorgum, millet, sugar cane and vegetables.