Controlled atmosphere treatment for control of grape mealybug, Pseudococcus maritimus (Ehrhorn) (Hemiptera: Pseudococcidae), on harvested table grapes

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 and <0.01μLL−1, 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 and ULO+CO2 treatments than nymphs and adults. A 14day ULO treatment with 30μLL−1 O2 at 2°C did not achieve 100% mortalities of any life stage. In the presence of 50% CO2, the 14d treatment achieved complete mortality of all life stages of the grape mealybug. A 3d ULO treatment with <0.01μLL−1 O2 at 2°C resulted in 93.3% mortality of nymphs and adults. The 3d 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 10d ULO+50% CO2 treatment with <0.01μLL−1 O2 at 2°C. Both the 14d CA treatment with 30μLL−1 O2 and 50% CO2 and the 10d CA treatment with <0.01μLL−1 O2 and 50% CO2 were tested on table grapes and grape quality was evaluated after two weeks of post-treatment storage. The CA treatments did not have a significant negative impact on grape quality and were safe for table grapes. The study indicated that CA treatments have potential to be developed for postharvest control of grape mealybug on harvested table grapes.