No effective spray program against the navel orangeworm—Pararnyehis transitella (Walker)—has been perfected. Therefore, control is dependent on orchard and plant management because the insect, primarily a scavenger, is capable of attacking sound walnuts after the husks have cracked.

The insect fungus—Beauveria bassiana—was identified by Edward A. Steinhaus, Professor of Insect Pathology, University of California, Berkeley.