LAUSR

The navel orangeworm (NOW), Amyelois transitella (Walker), is a major post‐harvest pest of tree nuts including walnut, almonds and pistachios. Nitric oxide (NO) was recently discovered to be a potential fumigant under ultralow oxygen conditions for post‐harvest pest control. In this study, NO fumigation was evaluated for efficacy against eggs, larvae and pupae of NOW. NO fumigation was found to be similarly effective against NOW on artificial diet and in infested walnuts. Fumigations of 4, 8 and 16 hr with 2.0, 1.0 and 0.5% NO, respectively, achieved complete control of small and large larvae in artificial diet. Complete control of pupae on artificial diet was achieved in 8, 16 and 24 hr fumigations with 2.0, 1.0 and 0.5% NO, respectively. For NOW in infested walnuts, complete control was achieved in 6, 8 and 16 hr fumigations with 1.5, 1.0 and 0.5% NO, respectively, for small larvae; in 4‐, 8‐ and 24‐hr fumigations with 2.0, 1.0 and 0.5% NO, respectively, for large larvae; and in 8‐, 16‐ and 24‐hr fumigations with 2.0, 1.0 and 0.5% NO, respectively, for pupae. Eggs were more tolerant to NO fumigation than larvae and pupae, and complete control of NOW eggs was achieved in 8‐ and 16‐hr fumigation with 3.0 and 2.0% NO, respectively. This study demonstrated the efficacy of NO fumigation against NOW on walnut and its potential as an alternative post‐harvest treatment for the pest.