Volatile compounds as insect lures: factors affecting release from passive dispenser systems

Knowledge about the behaviour of passive dispensers used to release semiochemicals for insect pest management is essential to ensure the efficacy of monitoring and control methods based on the use of the semiochemicals. The release characteristics of different passive dispenser types (commercial sachet, altered commercial sachet, polyethylene bags and cotton rolls) were investigated in the laboratory under various conditions. Using the volatile compound methyl isonicotinate (MI), a known lure for western flower thrips Frankliniella occidentalis (Pergande) and two additional homologues ethyl and n-propyl isonicotinate the effect of loading amount (0.5, 1.0 or 2.5 ml), temperatures (15°C, 25°C or 35°C) and air flow (0.1–0.15 m/s or 0.25–0.3 m/s) were tested in a low-speed laminar-flow wind tunnel. The results showed zero-order release kinetics for all tested dispenser types. Release rate kinetics relies on the type of molecule, dispenser type, and the climatic conditions with temperature being a major determinant of release rate. The results of the release characteristics of the different dispensers are discussed in regards to their practical use under greenhouse and field conditions.