PRELIMINARY RESULTS ON THE ANALYSIS OF VOLATILE AND NON-VOLATILE PHEROMONES IN CHILOCORUS NIGRITUS BY GC/MS

This study presents preliminary results on the analysis of the volatile and non-volatile compounds present in the scale insect Aspidiotus nerii, a notorious pest problem in crops, and the ladybird Chilocorus nigritus, a natural predator which can be used to control Aspidiotus nerii infestation. Potato tubers were used to rear Aspidiotus nerii uniparental and biparental populations. GC/MS was used to analyse volatile compounds collected from various insect cultures, as well as from control samples. Most of the volatiles observed appeared to be common to all samples, with one exception, 1,2- diethylbenzene, which was found in all samples except the controls and uniparental Aspidiotus nerii group. To investigate the presence of non-volatile compounds which could act as contact pheromones, Solid Phase Micro Extraction (SPME) samples were collected and analysed using GC/MS. Samples obtained from the ladybirdsʹ cuticles showed no compounds of interest to pheromone research. However, direct extraction of Chilocorus nigritus haemolymph (tissue fluid) in acetone identified an alkaloid compound similar to (+-) hippodamine. Although the biological function of this compound in Chilocorus nigritus has yet to be established, examples of the function of hippodamine in similar species suggest it could serve as an alarm pheromone or as an attractant kairomone.