Sulfur dioxide fumigation for postharvest control of mealybugs on harvested table grapes

Authors: Liu, Yong Biao

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/2/2018
Publication Date: 3/1/2019
Citation: Liu, Y. 2019. Sulfur dioxide fumigation for postharvest control of mealybugs on harvested table grapes. Journal of Economic Entomology. 112:597-602. https://doi.org/10.1093/jee/toy373.
DOI: https://doi.org/10.1093/jee/toy373

Interpretive Summary: Sulfur dioxide (SO2) fumigation treatments were conducted in ultralow oxygen conditions and in normal air to determine their effects on mortality of grape mealybug and vine mealybug, and on postharvest quality of table grapes in laboratory experiments. Effective control of all life stages was achieved in three and four-day fumigations with 100 parts per million (ppm) SO2, and in twenty-four hour fumigations with 300-500 ppm SO2 at 2°C. Nymph and adult stages of growth were more susceptible to SO2 fumigation treatments than eggs. Mortalities of vine mealybug eggs and nymphs/adults reached 100% in three and four-day fumigations with 100 ppm SO2 under ultralow oxygen conditions and in 24 h fumigation with 400 ppm SO2 in normal air. Egg mortality for grape mealybug ranged from 85.8 to 100%. None of the fumigation treatments had a negative effect on grape quality or percentage of marketable fruit. These results suggest that SO2 fumigation has potential to replace methyl bromide for postharvest pest control of harvested table grapes.

Technical Abstract: Laboratory fumigations with sulfur dioxide (SO2) were conducted under ultralow oxygen (ULO) conditions and normal atmosphere to determine their effects on mortality of grape mealybug, Pseudococcus maritimus (Ehrhorn), and vine mealybug, Planococcus ficus Signoret, and postharvest quality of table grapes. Three and four-day fumigation treatments with 100 ppm SO2 under 30 ppm ULO condition resulted in 100% mortality of eggs and nymphs/adults of the two insects. SO2 fumigations for the same durations in a normal atmosphere were also effective against grape mealybug with egg mortalities of 85.8% and 98.8% and nymph/adult mortalities of 99.0% and 100%, respectively. Twenty-four hour fumigation treatments with 400 and 500 ppm SO2 achieved 95% mortality of grape mealybug eggs and nymphs/adults, and =95% egg and 100% nymph/adult mortality for grape mealybug. None of the treatments used in this study adversely affected quality of the six different table grape cultivars used in the studies. SO2 fumigation under either ULO or normal atmosphere is potentially a useful means for postharvest control of these two mealybug species on table grapes.