Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 14, 2013
Publication Date: July 15, 2013
Citation: Liu, Y.-B. 2013. Controlled atmosphere treatment for control of grape mealybug, Pseudococcus maritimus (Ehrhorn) (Hemiptera: Pseudococcidae), on harvested table grapes. Postharvest Biology and Technology. 86:113-117. Interpretive Summary: Grape mealybug is a major pest on table grapes in U.S. and exported table grapes to overseas markets such as Australia requires quarantine treatments to control grape mealybug. The current treatment with methyl bromide fumigation impacts grape quality negatively as temperature of grapes needs to be raised well above the storage temperature. Methyl bromide fumigation is also unsustainable because its production is being phased out globally. In this study, two controlled atmosphere (CA) treatments with two ultralow oxygen (ULO) levels and 50% carbon dioxide were demonstrated to be effective in controlling all life stages of grapes mealybug and safe to postharvest quality of table grapes. CA treatments with only ULO without 50% carbon dioxide were less effective against grape mealybug. The ultralow oxygen levels were 30 ppm and <1 ppm and the lower oxygen level was more effective than the higher oxygen against grape mealybug. Grape mealybug eggs were more tolerant than nymphs and adults. This study indicates that it is feasible to develop safe and effective CA treatment to control grape mealybug on harvested table grapes.
Technical Abstract: Controlled atmosphere (CA) treatments with ultralow oxygen (ULO) alone and in combinations with 50% carbon dioxide were studied to control grape mealybug, Pseudococcus maritimus (Ehrhorn) on harvested table grapes. Two ultralow oxygen levels, ˜30 ppm and <1 ppm, were tested in both ULO and ULO+50% CO2 treatments. The ULO treatments with the lower oxygen level were more effective than the ULO treatments at the higher oxygen level. The ULO+50% CO2 treatments were more effective than the ULO treatments. Grape mealybug eggs were significantly more tolerant of ULO or ULO+CO2 treatments than nymphs and adults. A 14 day ULO treatment with ˜30 ppm O2 at 2°C did not achieve 100% mortalities of any life stage. In the presence of 50% CO2, the 14 d treatment achieved complete mortality of all life stages of the grape mealybug. A 3 day ULO treatment with <1 ppm O2 at 2°C resulted in 93.3% mortality of nymphs and adults. The 3 day ULO treatment in combination with 50% CO2 treatments, however, achieved complete control of grape mealybug nymphs and adults and caused 70.5% relative egg mortality. Complete egg mortality was achieved in a 10 day ULO+50% CO2 with <1ppm O2 at 2°C. Both the 14 d CA treatment with about 30 ppm O2 and 50% CO2 and the 10 d CA treatment with <1 ppm O2 and 50% CO2 were tested on table grapes and grape quality was evaluated after 2 wk of post-treatment storage. There was no significant negative impact on grape quality by the CA treatments and therefore, both treatments were safe to table grapes. The study indicated that CA treatment has a potential to be developed for postharvest control of grape mealybug on harvested table grapes.