A box of Chinese cabbage carrying a tiny but formidable threat to California agriculture was stopped at the Otay Mesa Port of Entry Thursday, federal officials said.
A non-native snail known to be destructive to farmers was found in the package of false pak choi during the inspection process.
The snail was found inside a cargo truck carrying a shipment of mixed produce from Mexico, agents said.
An agriculture specialist working with the U.S. Customs and Border Protection sent the snail off to the U.S. Department of Agriculture.
Experts said it was a Calcisuccinea aff. luteola (Gould), a mollusk that has been stopped at U.S. borders before but only a handful of times.
Agents denied the cargo truck entry and sent the shipment of produce back to Mexico.
Slugs and snails can attack a crop by eating seeds, stems or leaves and could create a large economic hardship for farmers across the state.
The University of California lists the native and non-native snails at nearly 300 and estimates the most damaging among them have arrived into to the U.S. through imports.