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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Research Project #439337

Research Project: Methyl Bromide Alternative Treatments for Perishable and Stored Products

Location: Crop Improvement and Protection Research

Project Number: 2038-22430-003-000-D
Project Type: In-House Appropriated

Start Date: Oct 1, 2020
End Date: Sep 30, 2025

The long-term objective of this project is the development of alternative postharvest treatments that are safe and effective for control of pests and microbes on fresh and stored products. This project builds upon our recent progress in developing nitric oxide (NO) fumigation treatments for control of pests and pathogens, and sulfur dioxide fumigation treatments for control of postharvest pests. Specifically, during the next five years we will focus on the following objective. Objective 1: Determine the effectiveness of nitric oxide and sulfur dioxide fumigation for postharvest control of pests and pathogens and evaluate the effectiveness of essential oils as alternative fumigants for postharvest pest control. Sub-objective 1A: Determine effectiveness of nitric oxide fumigation for control of microbes (pathogens) on stored products. Sub-objective 1B: Evaluate nitric oxide fumigation for control of insects and microbes (pathogens) in large-scale fumigation. Sub-objective 1C: Determine effective sulfur dioxide fumigation treatments against pests on fresh and stored products. Sub-objective 1D: Determine effective fumigation treatments with plant essential oils against postharvest pests.

Sub-objective 1A: Almonds, peanuts, and corn will be fumigated with nitrogen dioxide (NO2) in separate studies to determine microbial loads and effective treatments to control bacteria and fungi. Each product will also be disinfected with NO2 fumigation to kill bacteria and fungi and, then, artificially inoculated with spores of non-aflatoxin producing strain of Aspergillus flavus. Inoculated products will then be cultured and fumigated with NO2 to verify effective control of A. flavus. Sub-objective 1B: Large scale fumigation tests with NO + NO2 will be conducted in a 246 cm tall mini silo filled with corn to evaluate fumigant penetration and efficacy against rice weevil and Aspergillus flavus fungus. Rice weevil adults and A. flavus infected corn will be positioned at different depths in corn in the mini silo. An air pump will be used to circulate air in the mini silo. After injecting NO under specific ultralow oxygen conditions to have expected NO level for insect control and NO2 level for microbial control, NO and NO2 will be monitored at different heights of the mini silo. Efficacy against rice weevil and A. flavus will be evaluated at the end of fumigation treatment. Fumigations will be conducted with different combinations of NO and NO2 concentrations and treatment times to determine effective NO+NO2 fumigation for control rice weevil and the fungus. NO and NO2 levels will also be measured without air circulation to determine fumigant penetration in the mini silo. Sub-objective 1C: Small-scale SO2 fumigation tests will be conducted to determine effective combinations of SO2 concentrations and treatment times at different temperatures for control of rice weevil, confused flour beetle, naval orangeworm, and Pacific spider mite. Different life stages of insects/mites will be fumigated to determine the most tolerant life stages and effective treatments will be developed to control the most tolerant life stage for each pest. Once an effective treatment is identified, large-scale SO2 fumigation treatments will be conducted to control each pest on a selected product. Rice weevil, confused flour beetle, naval orangeworm, and Pacific spider mites will be fumigated together with corn, wheat, pistachio, and table grape, respectively, in large-scale SO2 fumigation treatments. The large-scale SO2 fumigation for controlling rice weevil will be conducted in the mini silo. Large-scale SO2 fumigation against other pests on respective products will be conducted in 26 l chambers modified from 7 gal plastic buckets. Sub-objective 1D: Rice weevil, navel orangeworm, and western flower thrips will be fumigated with plant essential oils (PEO) including anisole and methyl benzoate in glass jars. The pests at different life stages will be exposed to PEO at different doses for different durations at different temperatures to determine effective treatments. For each insect species, once an effective treatment is identified, it will be tested in larger scale fumigation tests with products to verify efficacy. For western flower thrips, effects of PEO fumigation on apple quality will also be evaluated in large-scale fumigation tests.