The Bolivian government has declared a state of emergency in a vast agricultural area affected by a plague of locusts.
The swarm first appeared over a week ago near the low-lying eastern city of Santa Cruz, where most of Bolivia's food and meat is produced.
It has spread quickly, destroying pasture and fields of corn and sorghum.
The authorities estimate more than 1,000 hectares of agricultural land have been devastated by the locusts.
The government says fumigation must begin straight away.
"We will create a 500-metre-wide ring around the area affected and fumigate inside, working alongside the local authorities," said Bolivia's Agriculture Secretary, Mauricio Ordonez.
Morales is due to visit Santa Cruz province on Friday.