The science of entomology (Insect Science)

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By Dr MC Bouwer
Insect Science

A new chemical ecology laboratory was built at Insect Science. This laboratory enables Insect Science to supply the agricultural sector with effective semiochemical-based management products.

Semiochemicals such as pheromones and allelochemicals are chemical messages that are produced in nature. These secret mes- sages are useful for behavioural manipulation of insect pest species, but it requires that the chemistry of the message is known before it can be mimicked artificially.

Semiochemical messages are encoded, not only in the identity of the chemical molecules that they are made of, but also in the relative blend ratios of the compounds that are re- leased into the atmosphere. It is thus neces- sary to mimic the natural messages accurately if these chemicals are implemented for insect pest control.

This is why Insect Science needed to invest in a chemical ecology laboratory. The chemi- cal ecology laboratory is equipped to enable researchers to find, identify and synthesise pheromone messages for those pest species that have not been thoroughly studied before. New insect pest species appear continuously in the agricultural sector both due to host range expansion of native insects and through the introduction of species that are not native to Southern Africa. Such insects are collect- ed from the field and brought back to the laboratory where a breeding colony is then established. The insect colony provides insects that can be studied in detail to identify their pheromone compounds.

Figure 1: Laboratory setup for sampling pheromones from insects. Here insects are sampled together with their food.

Figure 2: The electro antennogram detector with an insect antenna. This system allows researchers to know what insects smell.

A typical experiment starts when individuals of the insects are placed inside dynamic headspace sampling chambers where the volatile pheromones that they produce are sampled (Figure 1).

These samples are then screened for the presence of the pheromone compounds on the electro-antennogram detector (EAD) system (Figure 2). The electro-antennogram system allows researchers to know what insects can smell. The EAD uses the antenna of an insect as a chemical detector that can tell researchers which compounds, in complex blends, are the pheromones present in the samples. The identity of these compounds can then be elucidated and confirmed on the gas chromatography system linked to a mass spectrometer (GC-MS) (Figure 3) and nuclear magnetic resonance (NMR) systems.

Once the pheromone is known it can be synthesised and incorporated in new management products such as mating disruption devices or pheromone lures.

The quality of the products that are manu- factured at Insect Science is also assured through analysis in the newly built laboratory. Each batch of pheromone that is used in the products that are sold is tested for the chemical identity and purity of the active pheromone com- pound. The release rates of the pheromones from lures and other release devices are verified through gravimetrical and chromatographic methods (Figure 4).

Insect Science has also now recently obtained ISO 9001:2015 SANAS accreditation for the manufacture of pest management products. In this way, Insect Science can assure farmers that the products that are sold release their active compounds effectively in the field. These developments place Insect Science in a leading position for all chemical ecology-based pest management solutions in Southern Africa.

Figure 3: Gas chromatography-mass spectrometry (GC-MS) system at the Insect Science laboratory.

Figure 4: Sampling of volatiles from pheromone lures to estimate pheromone release rate from lure devices.

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