POSTHARVEST CONTROL OF Pseudococcus viburni (HEMIPTERA: PSEUDOCOCCIDAE) IN POMEGRANATES (Punica granatum) BY IMMERSION IN WARM DETERGENT SOLUTIONS

Abstract

The obscure mealybug Pseudococcus viburni is a major quarantine pest of pomegranates (Punica granatum) in Chile, causing significant rejections during postharvest fruit inspections. To develop alternative control measures, infested pomegranates were immersed in one of the sixteen post-harvest treatments, combining the following four factors in a completely randomized block design with a factorial structure: detergent concentration (0 and 1%), water temperature (15 or 47°C), pH (5.5 and 8.5), and exposure time (6 and 15 min). After immersions, pomegranates were stored for one month at cold storage (5°C) and followed by 24 h at room temperature. The number of total live mealybugs (survivorship) at different developmental stages (I, II, and III nymphal instars, and adult females) was counted. Water temperature had a significant effect in reducing total mealybug survival, but there were no significant interactions with remaining factors. Individually, detergent concentration, pH, and exposure time did not have statistically significant effects, but the interaction detergent x pH x exposure time (for all mealybugs) and detergent x pH (for II and III instar nymphs) reduced significantly mealybug infestation. While some treatments significantly reduced the population of P. viburni, with some treatment combinations reducing infestation up to 98%, there were always some survivors from all stages; therefore, no treatment satisfied international quarantine criteria for postharvest. It is important to note that the treatments did not affect fruit quality, suggesting that further evaluations of these factors at higher levels could be a promising avenue for pest control.