Donors are belatedly coughing up cash to fight locusts in West Africa, but agricultural experts warned on Monday that it will take two or three years to reduce the number of insects to the point where they no longer present a significant threat to agriculture. Nearly half the crop-spraying aircrafts in West Africa have been sent to Senegal. FAO officials and the representatives of European donors admitted on Monday that not enough has been done to control the largest locust invasion to hit West Africa for 15 years.