The chemistry of multitrophic interactions in phytoplasma disease systems and advances in control of psyllid vectors with semiochemicals

Phytoplasmas associated with the three most important diseases on fruit crops, ‘Candidatus Phytoplasma mali’ (apple proliferation), ‘Ca. P. pyri’ (pear decline), and ‘Ca. P. prunorum’ (European stone fruit yellows, ESFY), have been investigated for the chemistry of their interactions in a multitrophic context. The chemically mediated ecological interactions of the phytoplasmas with insect vectors (psyllids), their (alternate) host plants, pollinators and insect antagonists (entomopathogenic fungi) were studied. Attractive and repellent compounds were identified and tested in laboratory studies and field surveys. Additionally, a new entomopathogenic fungus was isolated from psyllid host. The identified new chemical compounds, blends and antagonists are used for the development of control strategies employing the complete spectrum of available methods and materials. Traps and dispensers, microencapsulated volatiles, and also nanofibers are used for the development of appropriate formulations for field applications of semiochemicals for phytoplasma vector control.