Wen made the call during his inspection tour of Henan Province, a major wheat-producing area in central China, from June 9 to 10.
He asked local governments to harvest crops as soon as possible, strengthen field management, intensify pest- and disease-prevention efforts, and ensure adequate supplies of fertilizers, pesticides and seeds.
Wen said a good summer harvest and stable farm produce prices are crucial for managing inflation expectations and for realizing the nation's macro-economic targets this year.
A bumper summer harvest will lay a solid foundation for the full-year harvest as summer grain output accounts for a quarter of annual grain output, he added.
Agriculture is a cornerstone for the national economy and the nation must always attach great importance to agricultural production, he said.