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

Authors: Walse, Spencer; Tebbets, John; LEESCH, JAMES - Former ARS Employee

Submitted to: Journal of Asia Pacific Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/29/2019
Publication Date: 5/23/2019
Citation: Walse, S.S., Tebbets, J.S., Leesch, J.G. 2019. Postharvest methyl bromide fumigation of Japanese plums to control codling moth (Lepidoptera: Tortricidae). Journal of Asia Pacific Entomology. 22(3):807-815. https://doi.org/10.1016/j.aspen.2019.04.011.
DOI: https://doi.org/10.1016/j.aspen.2019.04.011

Interpretive Summary: Codling moth is an insect pest that has impacted the export of key fruit crops, including fresh Japanese plums, from the United States to Japan. Postharvest fumigation provides a biological safeguard against insect and microbiological pests and, in many scenarios, is the only available tool for government and industry to guarantee pest-free security. This work addresses the need to develop a postharvest methyl bromide fumigation treatment to control this pest in multiple varieties of fresh Japanese plums that are of export interest to California growers. This work describes the fumigation parameters required for control and, importantly, also demonstrates that palletized cartons of fresh fruit can be shrouded with screen mesh prior to the fumigation to safeguard from further infestation. Moreover, the results of this research will promote more strategic technical and economic Quarantine Pre-shipment (QPS) uses of MB, a critical need for the United States per the international regulatory requirements of the Montreal Protocol.

Technical Abstract: Postharvest chamber fumigation with 48 mg/L(3.0 lbs/1000 ft3) methyl bromide (MB) for 2 hr 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. A series of pilot-scale exploratory 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 results in an MB exposure ca. 20% higher than that observed for fresh nectarines. Importantly, results from commercial-scale fumigations indicate that pallet shrouds will 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.