Combinatory effect of ethyl formate and phosphine fumigation on Pseudococcus longispinus and P. orchidicola (Hemiptera: Pseudococcidae) mortality and phytotoxicity to 13 foliage nursery plants

Abstract

Abstract Combinatory effect of ethyl formate (EF) and phosphine (PH3) fumigation against Pseudococcus longispinus and P. orchidicola was evaluated on 13 foliage nursery plants. Treatment with the combination of EF at 16 mg/L and PH3 at 0.1 mg/L for 4 h resulted in 100% fumigant activity against both adults and nymphs of P. longispinus and P. orchidicola in a 12 L desiccator. The combination treatment showed higher efficacy towards adults than towards nymphs for both mealybug species, although it was reversed for P. orchidicola when EF was treated alone. The combination treatment showed higher fumigant activity than the single EF or PH3 treatment. In larger fumigation chambers (0.65 m3 and 10 m3), 100% fumigant activity was observed with the combination of EF at 20 g/m3 and PH3 at 1 g/m3 against both mealybug species regardless of location inside chambers. The highest sorption rates for each fumigant were 24.4% for PH3-treated Hoya carnosa and 75.4% for EF-treated Philodendron selloum. Except P. selloum, all other species tested exhibited significant leaf damage one week after the combination treatment. Two species, Echeveria 'Perle von Nurnberg' and Heteropanax fragrans showed 100% leaf damage and died 5 months later without any new leaf formation. However, other 10 species were able to recover the treatment damage after 5 months. Treatment of these two plants with EF seems unfeasible. This study suggests that the combination of EF and PH3 can be used for controlling P. longispinus and P. orchidicola in some foliage nursery plants.