Phosphine and phosphine plus ethyl formate for controlling papaya mealybug (Hemiptera: Pseudococcidae) on succulents

The papaya mealybug, Paracoccus marginatus (Hemiptera: Pseudococcidae), poses a serious threat to global trade and is classified as a quarantine pest in some countries. Phosphine (PH3) is considered an alternative to methyl bromide for postharvest control of P. marginatus. However, reports addressing the impact of PH3 treatment to control P. marginatus on succulent plants are lacking. This study aims to investigate the effects of PH3 fumigation alone and in combination with ethyl formate (EF) on insecticidal activity across all developmental stages of P. marginatus and its influence on the quality of plant products. Tolerance tests showed that among all developmental stages, the egg stage of P. marginatus is the most tolerant to PH3 treatment. A concentration of 1 g m-3 PH3 for 8 h exposure at 25 °C achieved a 99.9968% (Probit-9) mortality rate for the eggs. Additionally, we examined the synergistic effects of combining EF with PH3. Combined fumigation with 0.5 g m-3 PH3 and 2 g m-3 EF for 8 h at 25 °C did not adversely affect the lifespan and quality of three succulent plant species, achieving an effective dose of 0.99991. These findings suggest that PH3 fumigation, with or without EF, are effective treatments for postharvest control of P. marginatus in succulent plants.