No abstract

Insect antennae are among the most sensitive and selective chemical-sensing organs in the animal kingdom. Insects can perceive picograms of specific volatile organic compounds per cubic meter of air in milliseconds, which is far below the detection thresholds of current analytical devices. These exceptional sensing abilities have many uses in the context of insect biotechnology. Living specimens or parts of them, such as isolated antennae or individual proteins, can serve as biosensors in the field. As volatiles occur in a crude mixture in the environment, knowing which trigger-volatiles are crucial for the insects' perception of specific incidents is of great value. This knowledge promotes the development of selective sensors for applications, such as fire detection. In this chapter, we discuss the different technical procedures for the preparation and use of insect-based biosensors for the detection of organic volatiles, including those based on insect behavior, insect olfactory proteins, and biomimetic sensing units. We also consider the use of these applications in portable devices outside the laboratory under field conditions.

Pheromones and other semiochemicals play an important role in the natural world by influencing the behavior of plants, mammals, and insects. In the latter case, species-dependent pheromone communication has numerous applications, including the detection, trapping, monitoring and guiding of insects, as well as pest management in agriculture. On-site sensors are desirable when volatile organic compounds (VOCs) are used as semiochemicals. Insects have evolved highly selective sensors for such compounds, so biosensors comprising complete insects, isolated organs or individual proteins can be highly effective. However, isolated insect organs have a limited lifetime as biosensor, so biomimetic approaches are needed for prolonged monitoring, novel applications, or measurements in challenging environments. We discuss the development of on-site biosensors and biomimetic approaches for airborne-pheromone sensing, together with biomimetic VOC sensor systems. Furthermore, the infochemical effect describing the anthropogenic contamination of the ecosystem through semiochemicals, will be considered in the context of novel on-site pheromone sensing-systems.

Mating disruption is a sustainable method for the control of insect pests, involving the release of synthetic sex pheromones that disrupt the olfactory localization of females by males. However, the development and refinement of this strategy is hampered because current instruments lack the sensitivity to detect volatile organic chemicals in the field, and portable electroantennograms produce non-comparable relative units and distorted results in the presence of plant volatiles. To address the demand for more sensitive instruments that are suitable for the rapid in situ detection of airborne pheromones, we have developed a portable, automated needle trap device connected to a gas chromatograph, mass spectrometer, and electroantennographic detector (NTD-GC-MS/EAD) suitable for field applications. We tested the instrument by measuring the concentration of the sex pheromone (E,Z)-7,9-dodecadienyl acetate, which is used to disrupt the mating of the European grapevine moth Lobesia botrana (Lepidoptera: Tortricidae). Our data confirm that the instrument generates highly reproducible results and is highly sensitive, with a detection threshold of 3 ng/m(3) (E,Z)-7,9-dodecadienyl acetate in outside air.

We present pheromone measurements of metal-oxide gas sensors in a laboratory setup using a 'selective odorant measurement of a multi-sensor array'. The array was equipped with commercial gas sensors and measured with constant temperatures and a temperature cycle to increase the sensitivity. To compare and to calibrate the measurement of insect pheromones, we used a portable GC-MS with an electro-antennographic detection system for insect antennae. In order to reach a proof of principles for the intended use of the system for in situ analyses in viticulture and the development of a portable biosensor, we tested the sensors with the main component E7,Z9-Dodecadien-1-yl acetate of the pheromone of the grapevine moth (Lobesia botrana).