Mauritania and Mali have issued preliminary estimates of heavy crop damage as governments across West Africa struggle to control a plague of locusts that is growing larger by the day. Mohamed Abdallahi Ould Babah, the director of Mauritania's locust control campaign told IRIN on Tuesday that hopper bands - concentrations of young flightless locusts - were invading fields in the southeast of the mainly desert country, destroying young shoots of sorghum, millet and beans.