Synergism of pheromone and host-plant volatile blends in the attraction of Grapholita molesta males (original) (raw)

2011, Entomologia Experimentalis et Applicata

Control of Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a major pest of stone and 2 pome fruits, is successfully achieved by mating disruption. Under these conditions, tools other 3 than conventional pheromone dispensers are needed for flight monitoring. The objective of 4 the present work was to determine whether plant volatiles synergize male G. molesta 5 attraction to a suboptimal dose of synthetic sex pheromone. The plant blend (5VB), a mixture 6 of three green leaf volatiles ((Z)-3-hexenyl acetate, (Z)-3-hexenol and (E)-2-hexenal), and two 7 aromatics (benzaldehyde and benzonitrile), was added to the suboptimal pheromone dose (2 8 ng on filter paper) in log steps (up to 10,000x the pheromone dose) to test synergism of 9 pheromone and plant blends. In addition, the effect of individual plant volatiles on male 10 responses was investigated by adding to the suboptimal pheromone dose each of the four-11 compound plant-volatile blends resulting from eliminating a different plant volatile from the 12 5VB at a time, or each plant volatile alone. Flight behaviour and the time to reach the source 13 were recorded. The 5VB alone was not attractive to G. molesta males, but at a ratio of 1:1000 14 (Ph:5VB) or higher increased the attractiveness of the suboptimal pheromone dose, to a level 15 similar to that of the optimal pheromone dose (10 ng). All tested plant volatiles, except 16 benzaldehyde, synergized the response to the pheromone when added individually, but only 17 (Z)-3-hexenol and benzonitrile did so to a level not significantly different from the Ph:5VB 18 blend. Aromatics had a stronger effect than GLVs, because their removal, but not the removal 19 of GLVs, decreased landing responses. The addition of the 5VB decreased significantly the 20 time males needed to reach the odour source. The observed enhanced male attraction to 21 mixtures of pheromone and plant volatiles will facilitate the development of lures for G. 22 molesta adult flight monitoring.