Postharvest methyl bromide fumigation of Japanese plums to control codling moth (Lepidoptera: Tortricidae)

Postharvest chamber fumigation with 48 mgL−1 (3.0 lbs./1000 ft3) methyl bromide (MB) for 2 h at pulp temperature (T) ≥ 21 °C and chamber load ≤50% is used to control codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in fresh nectarine, Prunus persica (L.) var. nucipersica, and French plum, P. domestica (L.), exports from California USA to Japan. Fumigations were conducted to verify that control of C. pomonella is expected following an analogous fumigation of fresh Japanese plums, P. salicina (Lindl.). A kinetic model, based on temporal measurement of MB levels in chamber headspace and how calculated exposures varied across the fumigation trials, showed that fresh Japanese plums and French plums sorb MB at a statistically equivalent rate, which resulted in an MB exposure ca. 20% higher than that observed for fresh nectarines. Importantly, results from commercial-scale fumigations indicate that pallet shrouds do not influence the efficacy of MB toward C. pomonella eggs, as their presence did not affect the rate of MB sorption, evidence that supports the use of pallet shrouds to safeguard against the potential for post-fumigation infestation in this export scenario, and beyond. Results are discussed in the context of graduation toward optimized quarantine fumigation schedules, which will promote more strategic technical and economic Quarantine Pre-shipment (QPS) uses of MB. [Display omitted] •Postharvest fumigation with methyl bromide (MB) controls eggs of Cydia pomonella•A schedule (48 mgL1 MB, 2 h, T ≥ 21 °C) was approved for P. domestica and P. persica.•Findings support MB fumigation for control of C. pomonella eggs on P. salicina.•Results identify how to evaluate relative treatment efficacy across all Prunus sp.•The pallet shrouds used in this study did not influence MB sorption or efficacy.