PHOSPHINE FUMIGATION TREATMENT FOR POSTHARVEST INSECT CONTROL ON LETTUCE
Crop Improvement and Protection Research
2012 Annual Report
1a.Objectives (from AD-416):
Develop low temperature phosphine fumigation treatment for control of lettuce aphid, leafminer, and western flower thrips on exported lettuce.
1b.Approach (from AD-416):
Small scale fumigation treatments using different phosphine concentrations and durations at a low temperature will be conducted to determine effective treatment to control each insect species. Selected fumigation treatments will be tested on commercial iceberg and romaine lettuce determine effects on postharvest quality of lettuce. Large pallet-scale fumigation treatment will be conducted to verify efficacy and safety of selected low temperature phosphine fumigation. Additional research will be conducted to determine suitability of using a phosphine generator for fumigation at low temperature and to find an economical way to conduct low temperature phosphine fumigation to control western flower thrips on lettuce.
The agreement was established to support and expand objective 2 of the in-house project to develop phosphine fumigation treatments to control pests on fresh products. Research was conducted to compare efficacy and phytotoxicity of regular and oxygenated phosphine fumigations for lettuce aphid control. Complete control of lettuce aphid was achieved in a 3-day fumigation with 2200 ppm phosphine under the normal oxygen level and in a 2-day fumigation with 1000 ppm phosphine under 60% oxygen at 2C. Oxygenated fumigation was found to have the advantages of shorter treatment time and lower phosphine dose. The 3-day regular fumigation caused significantly more injury to lettuce as indicated by the higher percentage of lettuce with injuries and lower internal quality as compared with the 2-day oxygenated phosphine fumigation. Oxygenated phosphine fumigation was, therefore, less phytotoxic than regular phosphine fumigation to lettuce. Additionally, a phosphine generator was unsuitable for low temperature phosphine fumigation due to phytotoxicity in 1-day and 3-day treatments of harvested lettuce.