Measurement of semiochemical release rates with a dedicated environmental control system

• Environment control system developed to measure semiochemical release rates.
• Semiochemical release rate increases exponentially with ambient temperature.
• Release rate not apparently affected by relative humidity.
• System can predict lifetime of semiochemical devices in agriculture and forestry.

Insect semiochemical dispensers are commonly deployed under variable environmental conditions over a specified period. Predictions of their longevity are hampered by a lack of methods to accurately monitor and predict how primary variables affect semiochemical release rate. A system was constructed to precisely determine semiochemical release rates under environmentally-controlled conditions. Three dissimilar types of solid matrix, passive emission semiochemical dispensers (P339 Sirex, Beetleblock-MCH, W230 terpinolene) were selected to verify the system capabilities. The rate of mass loss for each semiochemical was measured inside a 0.11 m3 air sealed reservoir. Each product was tested at five ambient temperatures and three values of relative humidity. Temperatures were maintained at their set points within ±1.0 °C and relative humidity within ±0.4%. Mass losses for the relatively large P339 Sirex dispensers were linear over the test period; losses for the smaller Beetleblock-MCH and W230 terpinolene dispensers fell sharply over the first 10 h of exposure and then fell linearly with exposure time. Test results demonstrated that release rates of the three semiochemicals at the linear fall stage increased exponentially as ambient temperature increased, and those rates were not apparently affected by relative humidity. Compared to release rates measured under field conditions, determination of semiochemical release rates was more precise and consistent with this dedicated, controlled environmental system. Semiochemical release rates measured with this system should provide a baseline for predicting performance and useful lifetime of semiochemical devices deployed for pest management in agriculture and forestry.