WASCO, Calif.—Residents of the agriculture-rich Central Valley are falling victim to Covid-19 at the highest rates in California, endangering a largely immigrant workforce during harvest season and helping drive the state’s persistently high infection rate.

As America’s most populous state struggles to contain the spread of the coronavirus, Gov. Gavin Newsom has identified the Central Valley as a key area of concern, sending $52 million in additional aid.

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