Sulfur dioxide (SO2) has a long history of being used in agriculture including food preservation, microbial control, and pest control. However, there is very little commercial use of SO2 for postharvest pest control. As methyl bromide has been phased out, alternative fumigants are urgently needed to meet the need of postharvest pest control. We studied SO2 fumigation for postharvest pest control in last several years and found that SO2 fumigation has good potential to be used for postharvest pest control on fresh and stored products. We successfully controlled mealybugs on table grapes and navel orangeworm on stored pistachios with SO2 fumigation. All life stages of vine mealybug and grape mealybug were completely controlled in 4-day fumigations with 100 ppm SO2 at 2°C. One-day fumigation treatments with 400 and 500 ppm SO2 achieved 89.8% and 95.8% mortality of grape mealybug eggs, respectively, and achieved 100% mortality of grape mealybug nymphs and adults. All treatments were safe to postharvest quality of table grapes. For navel orangeworm, there are considerable variation in susceptibility to SO2 fumigation among different life stages. Three-hour fumigations with 0.2, 2, and 1% SO2 achieved complete controls of eggs, larvae, and pupae respectively at 20°C. Complete control of large larvae in infested pistachios was also achieved in 3 h fumigation with 1.6 – 1.8% SO2 of pistachios. These studies showed that SO2 has potential to be an effective alternative fumigant for postharvest pest control on fresh and stored products.
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