LOS ANGELES (WCMH) — The debate on immigration has been hitting America’s farms, which are now losing millions in lost crops due to a shortage of agricultural migrant workers.

Nine in 10 farm workers in California are foreign-born, with many of them coming from Mexico. But according to the PEW Research Center, more Mexican immigrants are now leaving the U.S. than arriving.

Farmers tell NBC News the labor shortage is so severe, they’ve had to leave entire fields of vegetables unharvested. In just two counties in California, that’s led to a loss of more than $13 million.

Now, farmers are paying well above minimum wage, offering 401K plans, paid time off, and other incentives to try to lure workers back to the fields. They are also calling on politicians to pass laws to allow guest visa programs during harvest times.