Location: Crop Improvement and Protection Research
2018 Annual Report
Objectives
The long-term goal of this project is to develop alternative postharvest pest control treatments that are effective and safe for control of quarantine pests on a wide range of perishable agricultural commodities. This project builds upon our previous success with nitric oxide (NO) and oxygenated phoshine (PH3) fumigations as potential alternatives to methyl bromide fumigation for postharvest pest control on fresh fruits and vegetables. Nitric oxide was found to have higher efficacy than regular PH3 and may also enhance postharvest quality of fresh products. Oxygenated PH3 fumigation was found to control external pests with greater efficacy than regular PH3 fumigation. Successful completion of the project will result in specific NO fumigation and oxygenated PH3 fumigation treatments against four insect species on fresh fruit and vegetables including western flower thrips, light brown apple moth, codling moth, and the fruit fly spotted wing drosophila. Specific objectives are listed below:
Objective 1. Develop nitric oxide fumigation treatments for postharvest pest control.
Sub-objective 1.A. Develop an effective nitric oxide fumigation treatment to control western flower thrips on fresh fruit and vegetables.
Sub-objective 1.B. Develop an effective nitric oxide fumigation treatment to control light brown apple moth on fruit.
Sub-objective 1.C. Develop an effective nitric oxide fumigation treatment to control codling moth in apples.
Sub-objective 1.D. Develop an effective nitric oxide fumigation treatment to control spotted wing drosophila in sweet cherries and strawberries.
Objective 2. Develop oxygenated phosphine fumigation treatments for postharvest pest control.
Sub-objective 2.A. Determine feasibility of oxygenated phosphine fumigation to control codling moth in apples.
Sub-objective 2.B. Determine feasibility of oxygenated phosphine fumigation to control spotted wing drosophila in strawberries.
Approach
Objective 1. Nitric oxide fumigation under ultralow oxygen conditions will be studied for controlling insect pests including western flower thrips, light brown apple moth, codling moth, and spotted wing drosophila on harvested fresh commodities for their exports. Small scale laboratory fumigations will be conducted to determine effective treatments (concentration, time, and temperature) for different insects. Selected treatments will then be tested on specific fresh products to evaluate the impact of the treatments on postharvest quality.
Objective 2. Oxygenated phosphine fumigation under high oxygen conditions will be studied for controlling codling moth larvae in apples and spotted wing drosophila in sweet cherries and strawberries. Small scale laboratory fumigations will be conducted to determine effective treatments to control the most tolerant life stages of the pests in the fruits. Selected effective treatments will then be tested on fresh products to verify their efficacies and impact of postharvest quality of the fresh products.
Progress Report
Scientists are continuing to determine residues of nitric oxide fumigation in stored products to provide necessary data for eventual registration of nitric oxide as a pesticide for postharvest pest control. Understanding residues of nitric oxide fumigation is important to determine the potential impact of nitric oxide fumigation on food safety and registration of nitric oxide with the U.S. Environmental Protection Agency (EPA) for postharvest pest control. Over 10 stored products including beans, nuts, rice, and wheat have been analyzed for nitrate and nitrite residues from nitric oxide fumigation treatments.
Research was conducted to determine effectiveness of nitric oxide fumigation in controlling microbials on fresh and stored products. When nitric oxide fumigation is conducted under ultralow oxygen conditions, some nitric oxide reacts with oxygen in the fumigation chamber to produce nitrogen dioxide. By controlling ultralow oxygen levels in nitric oxide fumigation, different levels of nitrogen dioxide can be produced for microbial control. Preliminary results showed that nitric oxide fumigation was effective against spores of the fungus Aspergillus flavus and reduced the overall microbial load on strawberries. The research is continuing to develop nitric oxide fumigation treatments that control both target pests and pathogens on fresh and stored products, thus expanding applications of nitric oxide fumigation.
Research was also conducted to evaluate methyl benzoate as an alternative fumigant for postharvest pest control on fresh products. A preliminary study determined efficacy of methyl benzoate fumigation against western flower thrips on apples. Complete control of thrips was achieved and the fumigation treatment did not affect apple quality. More research efforts will be focused on this chemical to determine its potential as an alternative fumigant for postharvest pest control.
Accomplishments
1. Nitric oxide fumigation treatment to control spotted wing drosophila in strawberries. Spotted wing drosophila is an important pest in harvested small fruits, requiring treatment for export markets. Working with a newly discovered fumigant, nitric oxide, an ARS researcher at Salinas, California, in collaboration with an entomologist at the University of California developed a safe and effective nitric oxide fumigation to control the pest in strawberries. In a laboratory study, 8 hours of nitric oxide fumigation at 3% under ultralow oxygen conditions had effective control of spotted wing drosophila with 100% mortality of eggs and larvae and 98.8% mortality of pupae at a low storage temperature of 2° Celsius. A 16-hour fumigation with 3% nitric oxide had no negative effects on strawberry quality and reduced mold on strawberries. The study showed that nitric oxide fumigation has the potential for controlling spotted wing drosophila in strawberries as well as extending strawberry storage and shelf-life.
2. Nitric oxide fumigation treatment to control lettuce aphid and western flower thrips on lettuce. An alternative treatment to methyl bromide is needed to control quarantine pests, including lettuce aphid and western flower thrips, on lettuce exported to Asian markets. An ARS researcher in Salinas, California, in collaboration with an entomologist from the University of California at Davis, successfully demonstrated that nitric oxide fumigation was effective and safe to control both pests on commercial packed lettuce. Nitric oxide fumigation needs to be conducted under ultralow oxygen conditions and fumigation chambers must be flushed with nitrogen to dilute nitric oxide before terminating the fumigation in order to prevent injuries to sensitive products because nitric oxide reacts with oxygen to produce nitrogen dioxide, which is injurious to lettuce. Commercial packaging of fresh products restrict ventilation and may affect the process of establishing ultralow oxygen at the start and diluting nitric oxide at the end. In this study, 16 hours of fumigation with 0.5% nitric oxide was identified to be effective and safe in controlling both insect species on commercial packed lettuce in a large-scale laboratory experiment. These results suggest that nitric oxide fumigation has potential to be used to control both insects on harvested lettuce.
3. Sulfur dioxide fumigation treatment to control mealybugs on harvested table grapes. Grape mealybug and vine mealybug are important vineyard pests and require treatment on harvested table grapes. ARS researchers in Salinas, California, found that sulfur dioxide (SO2) fumigation was safe and effective in controlling both mealybugs on harvested table grapes. Sulfur dioxide has not been used traditionally as a fumigant for pest control. In this laboratory study, three- and four-day fumigations with 100 parts per million (ppm) SO2 and 24 hour fumigations with 400-500 ppm SO2 were effective against all life stages of the two mealybugs with over 95% mortality for eggs and 100% mortality for nymphs and adults. None of the effective treatments had any negative impacts on table grape quality. These results suggest that sulfur dioxide has potential for postharvest pest control on harvested table grapes.
Review Publications
Liu, Y. 2017. Nitric oxide fumigation for control of bulb mites on flower bulbs. Journal of Economic Entomology. 110(5):2046-2051. https://doi.org/10.1093/jee/tox187.
Liu, Y.-B., Yang, X., Masuda, T. 2017. Procedures of laboratory fumigation for pest control with nitric oxide gas. Journal of Visualized Experiments. 129:e56309. https://doi.org/10.3791/56309.
Liu, Y. 2018. Low temperature fumigation of harvested lettuce using a phosphine generator. Journal of Economic Entomology. 111(3):1171-1176. https://doi.org/10.1093/jee/toy038.
Yang, X., Liu, Y. 2018. Nitric oxide fumigation for control of spotted wing drosophila (Diptera: Drosophilidae) in strawberries. Journal of Economic Entomology. 111(3):1180-1184. https://doi.org/10.1093/jee/toy074.
Yang, X., Liu, Y.-B. 2018. Nitric oxide fumigation for postharvest pest control on lettuce. Pest Management Science. https://doi.org/10.1002/ps.5123.
