Long-lasting repellent activities of eco-friendly polyurethane system for controlled citral against melon fly

Using plant essential oil instead of chemical pesticides to control melon fly ( Bactrocera cucurbitae (Coquillett)) is still a great challenge in agricultural practices, which must effectively slow down the volatility rate of plant essential oil. In this study, citral as a natural plant essential oil was blended with environmentally friendly castor oil based waterborne polyurethane (PU). The interaction, chemical resistance, adhesion property and sustained release behavior of the composites with different citral content were clarified, and the efficacies against the melon fly under field conditions were explored. The results indicated that the composites prepared exhibited excellent adhesion behavior on bitter gourds ( Momordica charantia L.) even under rainfall washing, meanwhile the chemical resistance of composites could be tailored via controlling citral content. Low citral content composite films could be washed off by alcohol without worrying about the safety of that on crops. The composite prepared exhibited long-lasting repellent behavior against melon fly. The composite can be prepared via a simple technology and low cost, which has great value for plant essential oil applied in agriculture and can provide a new approach for melon fly control.