Development of innovative methods for trapping of phytoplasma vectors by attractive infochemicals

Some examples of attempts to develop biotechnical control methods for psyllids vectoring fruit tree phytoplasmas by sticky traps lured with newly detected infochemicals are reported. The apple psyllid Cacopsylla picta is the main vector of 'Candidatus Phytoplasma mali', the agent associated with apple proliferation disease in Germany and most neighbouring countries. Complex interactions between Malus domestica, the psyllid C. picta, and the phytoplasma were investigated in laboratory and field experiments. Results showed that emigrants of C. picta are able to distinguish the odours of healthy and infected apple trees and preferred the odours of infected trees. This means that the phytoplasma directly manipulates both the plant physiology by producing an attractive compound, and the psyllid behaviour, resulting in a better spread within its host plant population. The compound responsible for the attraction of the vector was collected from the headspace of infected apple plants and identified by gas chromatography coupled with mass spectrometry. It attracted both genders of C. picta and will be used for the development of traps for monitoring or mass trapping.