Location: Crop Improvement and Protection Research2012 Annual Report
1a. Objectives (from AD-416):
1. Develop controlled atmosphere treatments for postharvest pest control on perishable commodities. A) Develop semi-commercial scale storage and ultralow oxygen combination treatment for control of western flower thrips on head lettuce. B) Develop semi-commercial scale storage and ultralow oxygen combination treatment for control of western flower thrips on broccoli. C) Develop controlled atmosphere treatment for control of mealybugs and black widow spiders on table grapes. D) Develop ultralow oxygen treatment for control of vine mealybug on grape rootstocks. 2. Develop pure phosphine funigant treatments for highly perishable commodities. A) Develop fumigation treatment with pure phosphine for control of western flower thrips on lettuce, broccoli, asparagus, and strawberries. B) Develop fumigation treatment with pure phosphine for control of lettuce aphid and leafminer on lettuce. C) Develop fumigation treatments with pure phosphine for control of mealybugs and spiders on table grapes.
1b. Approach (from AD-416):
The minimum duration of pre-treatment cold storage needs to be determined in order to reduce the overall duration for completing ULO treatment and make it possible for pre-export ULO treatments. Effectiveness of ULO treatments for thrips control and their effect on postharvest quality of lettuce needs to be determined in large-scale tests. Oxygen consumption rates and oxygen demands by lettuce need to be determined in large-scale trials for commercial application. Efficacy and safety of ULO treatment for control of western flower thrips on broccoli.
3. Progress Report:
This is the final report for the project 5305-43000-003-00D. This project includes two parts: controlled atmosphere treatments and low temperature phosphine fumigation treatments for postharvest pest control on perishable commodities under Objectives 1 and 2. Under Objective 1A, head lettuce was found to tolerate ultralow oxygen (ULO) treatment for control of western flower thrips after they were stored for two or more days after harvest. Under Objective 1B, western flower thrips were successfully controlled on broccoli in a pallet scale ULO treatment at a low temperature of 1C in 5 days without injury to product quality. Under Objective 1C, a one-day ULO treatment with 0.5% oxygen was found to be safe and effective in controlling black widow spiders on table grapes. Effective CA, treatment with ULO in combination with 50% CO2 was found to be safe and effective in controlling all life stages of grape mealybug on table grapes. Under Objective 1D, safe and effective ULO treatments were found to control all life stages of vine mealybug on grape rootstocks. The treatment can be an alternative to the current labor intensive hot water dipping treatment. Under Objective 2A, low temperature phosphine fumigation treatment for western flower thrips was developed and the treatment was safe to lettuce, broccoli, asparagus, and strawberries. A commercial scale refrigerated container fumigation trial was also conducted to determine feasibility of shipping container fumigation. Under Objective 2B, studies were conducted to determine effective treatments for controlling lettuce aphid and leafminer and safety to lettuce quality. Lettuce aphid was effectively controlled in a 3 day fumigation with phosphine at a high concentration. But the treatment also resulted in significant lettuce quality degradation. Under Objective 2C, studies were conducted to determine effective treatment to control mealybug eggs, and grape mealybug eggs were found to be very tolerant to low temperature phosphine fumigation. The most important accomplishment of this project, however, is the finding that oxygen enhances phosphine toxicity and development of oxygenated phosphine fumigation method. Oxygenated phosphine fumigation was found not only more effective against insects than regular phosphine fumigation but also less phytotoxic because of reduced treatment time and shorter treatment durations as compared with regular phosphine fumigation. We further demonstrated that some insects/life stages such as light brown apple moth eggs could not be controlled with regular phosphine fumigation but can be controlled with oxygenated phosphine fumigation.
1. Oxygenated phosphine fumigation for postharvest pest control. Phosphine is a practical alternative to methyl bromide, but it is not effective against some tolerant insects and phosphine fumigations can last over ten days to control some insects. Researchers at USDA-ARS in Salinas, California, found significant synergistic effects of oxygen in increasing toxicity of phosphine against all life stages of various insects and developed oxygenated phosphine fumigation method. Oxygenated phosphine fumigation was demonstrated to significantly reduce treatment time and phytotoxicity and achieve effective control of tolerant insects that cannot be controlled with regular phosphine fumigation. Oxygenated phosphine fumigation has potential to make significant impact on fumigation industry.
2. Responses of light brown apple moth to phosphine fumigation. Light brown apple moth (LBAM) has potential to severely disrupt U.S. export of fresh fruits and vegetables as it established and spreads in California and beyond. Researchers at United States Department of Agriculture/Agriculture Research Station in Salinas, California, found that oxygenated phosphine fumigation can effectively control LBAM eggs within three days while regular phosphine fumigation failed in achieving control of LBAM eggs in four days. This study further demonstrated the advantage of oxygenated phosphine fumigation over the regular phosphine fumigation. The study indicated that effective control of LBAM with oxygenated phosphine fumigation is feasible and the treatment has the potential to provide much needed solution for the control of LBAM on exported fresh products.
3. Low temperature phosphine fumigation to control western flower thrips on fresh vegetables and fruits. Fresh products for export to Taiwan often require fumigation treatments to control western flower thrips. To address this quarantine problem, researchers at United States Department of Agriculture/Agriculture Research Station in Salinas, California, conducted research to develop low temperature phosphine fumigation to control thrips on lettuce, broccoli, asparagus, and strawberries. Pure phosphine fumigation at a low temperature was demonstrated to be effective in controlling western flower thrips. It was safe on all of the commodities tested and provided a solution to thrips quarantine problem on exported fresh products for industry to use.
4. Ultralow oxygen treatment to control black widow spiders on harvested table grapes. Black widow spiders have been found hitchhiking on harvested table grape clusters and pose safety hazards to workers as well as consumers and require treatments on exported table grapes on some overseas markets. Researchers at USDA-ARS in Salinas, California, successfully developed a ultralow oxygen treatment for controlling of black widow spiders on table grapes without any negative effects on grape quality. Black widow spiders were found to be very susceptible to oxygen deficiency, and one day exposure to atmosphere with 0.5% oxygen or at low temperature was found to be adequate for successful control of the spiders. Because of short treatment time and low temperature and easily attainable oxygen level, the treatment has good prospect of being used commercially.
5. Ultralow oxygen treatment to control western flower thrips on lettuce. The lack of safe and effective postharvest control of western flower thrips is a major obstacle for export of U.S. fresh commodities including lettuce to Taiwan. Scientists at USDA-ARS in Salinas, California, conducted research to develop ultralow oxygen (ULO) treatment as a methyl bromide alternative to control the pest on harvested lettuce. Following the previous progress showing that fresh lettuce was susceptible to a 2-day ULO treatment but lettuce which has been stored for one week before ULO treatment tolerated ULO treatment, it was found that 3-day storage was sufficient to prevent injury by the ULO treatment for control of western flower thrips. Pallet scale ultralow oxygen (ULO) treatment was conducted with lettuce of different cultivars and complete control of thrips was achieved without negative effects on lettuce quality. The research reduced overall time needed to complete ULO treatment and thereby made the ULO treatment more practical for commercial adoption.
6. Controlled atmosphere treatment for postharvest insect control on harvested table grapes. Exported table grapes often face phytosanitary barriers on overseas markets as they harbor quarantined insects such as western flower thrips and grape mealybug. Researchers at United States Department of Agriculture/Agriculture Research Station in Salinas, California, conducted research to develop California treatments. A 3-day ultralow oxygen (ULO) treatment at 3°C was demonstrated to be effective in controlling the thrips and a California treatment with a combination of ultralow oxygen (<1 ppm) and elevated carbon dioxide (50%) was found to control grape mealybug eggs in 10 days at 2°C. Both treatments were safe to postharvest quality of harvested table grapes. The study demonstrated that it is feasible to control grape mealybug on table grapes using California treatment and table grapes had very high tolerance to California treatment. The ULO treatment for thrips control has potential to be used on exported organic table grapes.
7. Ultralow oxygen treatment to control vine mealybug on grape rootstocks. Vine mealybug, a major pest of vineyards, is difficult to control on grape rootstocks with foliar pesticide spray and is currently controlled with hot water dipping of dormant rootstocks after harvest which is labor intensive and expensive. Researcher at United States Department of Agriculture/Agriculture Research Station in Salinas, California, successfully developed an ultralow oxygen (ULO) treatment to solve the vine mealybug problem. The pest was controlled by storing rootstocks with vine mealybug under nitrogen with little or no oxygen for three or four days at 25 or 15°C respectively, which resulted in 100% mortality of all life stages. The treatments had no negative effects on rootstock germination and growth, and therefore provided a safe, effective, and economical alternative to the hot water immersion treatment for control of vine mealybug.
Liu, Y-B. 2012. Ultralow oxygen treatment for control of western flower thrips, frankliniella occidentalis (thysanoptera: thripidae), on harvested table grapes. Journal of Asia-Pacific Entomology. 15:269-271.