D3347: Comparison phosphine efficacy to the citrus mealybug, Planococcus citri, depending on the various temperature conditions

In 1989, Methyl bromide (MB) has been designated as an ozone-depleting substance in the Montreal Protocol and has only been available for use in quarantine. Phosphine, one of the MB alternative fumigants, has the advantage of being safe for fresh food due to its low phytotoxicity at low concentrations compared to other fumigants, but it has the disadvantage of long fumigation time. In this study, the efficacy of phosphine was compared when eggs, nymphs and adults of Planococcus citri were treated at various temperature conditions, 5, 10, 13, and 20 °C. In addition, its phytotoxicity on orange treated at 5 °C was investigated. When oranges treated 0.05-2.00 mg/L phosphine at 5 ℃ for 20 hours, phosphine had a effect on the orange color after 30 days of treatment. However, other indices, such as sugar content, decay rate, and weight loss rate, were not significantly different. In the comparison of phosphine efficacy in the various temperature, the highest toxicity was exhibited in all stages of P. citri at 20 ℃ for 20 hours compared to other temperature. Among different stages of P. citri, egg, nymph, and adult, eggs showed the highest resistance. In the present study, efficacy of phosphine to P. citri in the various temperature treatment conditions was compared, but further studies on treatment time for application of phosphine in the quarantine fields are needed.