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 Crop Improvement and Protection Research: Salinas, CA
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ARS Home Pacific West Area Salinas, California Crop Improvement and Protection Research Research





- Liu, Yong Biao
- Leblanc, Nicholas
- 2023
- 2022
- 2021
- Publications
- Crop Protection & Quarantine (304)

Research Project: Methyl Bromide Alternative Treatments for Perishable and Stored Products **Location:
                            Crop Improvement and Protection Research** 2023 Annual Report **Objectives**
                                

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. **Approach**
                                

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. **Progress Report**
                                

Research on sulfur dioxide (SO2) fumigation for control of stored product insects is continuing. Effective 3 hour SO2 fumigation treatments were determined for control of rice weevil and confused flour beetle adults. Confused flour beetle adults were more susceptible to SO2 fumigation than rice weevil adults. Complete control of confused flour beetle adults was achieved in 3 hour fumigation with 1 percent (%) SO2, and 3 hour fumigation with 1.5% SO2 had 96.7% mortality of rice weevil adults. This research is continuing to determine susceptibility of other life stages to SO2 fumigation and effective SO2 fumigation treatments.

Research on SO2 fumigation for control of western flower thrips on fresh fruits is in progress. An effective treatment was identified, and the treatment is being tested on fresh fruits to determine potential impact on fruit quality.
 
Research on SO2 fumigation for control of spotted wing drosophila (SWD) on blueberries is in progress. Preliminary data indicates that SO2 is effective against SWD flies and larvae in infested blueberries. Effects of SO2 fumigation on blueberry quality will be investigated. These studies are directly related to Sub-objective 1C.

Research was also conducted to explore new essential oil fumigants for postharvest pest control. Nine compounds were selected and screened based on their molecular characteristics, vapor pressures, and past research to determine their potential effects on insect mortality. An effective candidate was identified and evaluated for postharvest control of different pests including rice weevil, confused flour beetle, spotted wing drosophila, western flower thrips, and eastern subterranean termites. Complete control of western flower thrips with fresh fruit was achieved in 3 hour fumigation at 5C. Preliminary tests were also conducted to determine effects of fumigation with the essential oil on postharvest quality of apples, navel oranges, broccoli, green beans, bell peppers, and asparagus, and no negative effects on product quality have been identified yet. This research is directly related to Sub-objective 1D. 

Research was also conducted on control of Verticillium pathogen in spinach seeds using nitrogen dioxide fumigation in collaboration with another scientist in Salinas, California. Preliminary experiments showed satisfactory control of the pathogen in three-day fumigations with 3% nitrogen dioxide (NO2). **Accomplishments**
                                

1. Sulfur dioxide fumigation for control of navel orangeworm on stored pistachios. Navel orangeworm (NOW) is a major pest of stored tree nuts including pistachios in California. Sulfur dioxide (SO2) fumigation was evaluated as an alternative treatment for postharvest control of NOW on stored pistachios. ARS scientists at Salinas, California, measured sorption of SO2 on pistachios at different temperatures, and pistachios were found to have high sorption of SO2 over time. Because of rapid sorption of SO2, 3-hour short fumigations were conducted to develop an effective SO2 fumigation treatment against NOW, and SO2 fumigation was effective against NOW at different life stages. Complete controls of eggs, larvae, and pupae were achieved in 3-hour fumigations with 0.2, 2.0, and 1.0% SO2, respectively, and large-scale 3-hour fumigations of pistachios with 1.6-1.8% SO2 had complete control of 6th instar larvae in infested pistachios. The results showed that SO2 fumigation has potential to control NOW on stored pistachios as well as to control other postharvest pests on stored products. 2. Compost suppresses a common soilborne plant pathogen of lettuce. Soilborne plant pathogens are a significant constraint on lettuce production in California, valued at $2 billion dollars a year. Soil fumigation is too expensive for lettuce growers and is incompatible with organic production standards. ARS researchers at Salinas, California, showed that adding compost to soil reduces the abundance of the soilborne lettuce pathogen Fusarium oxysporum. Results from this research provide growers with methods to reduce a common soilborne plant pathogen of lettuce. **Review Publications**
                            *Liu, Y.-B. 2023. Efficacy and sorption of sulfur dioxide as a fumigant for control of navel orangeworm (Amyelois transitella) on stored pistachios. Journal of Stored Products Research. 102. Article 102109. https://doi.org/10.1016/j.jspr.2023.102109.*
                                *LeBlanc, N.R., Salgado-Salazar, C. 2023. Genome sequence resources for Verticillium dahliae-inhibiting Streptomyces spp. isolated from agricultural soil. PhytoFrontiers. https://doi.org/10.1094/PHYTOFR-10-22-0116-A.*


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