The electrophysiological and behavioural responses of the aphidophagous hoverfly
Episyrphus balteatus Degear, and polyphagous ground beetles Pterostichus
melanarius Illeger and Nebria brevicollis Linneaus, to a range of volatile
semiochemicals were studied. Phacelia tanacetifolia flower extract, Nepeta catarici
whole plant extract, (E)-P-farnesene, and food supplement sprays where found to be
attractive to the predators in laboratory and wind tunnel assays.
Field trials demonstrated that the attractive semiochemicals could be placed in
dispensers in arable crops to increase the amount of predators present throughout the
field system. There was also a corresponding decrease in the number of pest species
present in the treated field plots relative to the control plots. Phacelia flower extract
was found to have the greatest effects on predator and prey numbers.
The mechanisms of the reduction in prey numbers were studied using exclusion
experiments in the field and Enzyme linked immunosorbant assays. There was found
to be a link between the increased rates of predation in the field and the decline in