This economic disease is affecting California farmers amid a historic drought that is threatening future harvests in the state.

"We're at the mercy of foreign shipping companies," said Roger Isom, president of the California Cotton Ginners and Growers Association and the Western Agricultural Processors Association.

California is one of the country's main agricultural regions. It is the nation's only supplier of tree nuts such as walnuts, pistachios and almonds. Most of the tree nuts grown here are exported to other countries. According to the California Department of Food and Agriculture, in 2019 the export of tree nuts alone netted the country more than $8.1 billion.

But the heavy congestion at the state's main ports is preventing farmers from being able to send out most of their agricultural products. (Related: Truck driver warns supply chain crisis will not end unless port congestion, labor shortage and other long-term issues are resolved.)