Nadia Baldassari

Geographic variation in the field response of male European pine sawflies, Neodiprion sertifer, to different pheromone stereoisomers and esters.

The European pine sawfly, Neodiprion sertifer (Geoffroy) (Hymenoptera: Diprionidae), is a widespread and economically important forest insect. The sex pheromone communication system of this species has been previously investigated in North America, Japan and Europe, with the acetate or propionate of the alcohol (2S,3S,7S)‐3,7‐dimethyl‐2‐pentadecanol (diprionol) shown to be the main pheromone component. In some locations, male attraction either increased or decreased by the addition of the (2S,3R,7R)‐diprionyl acetate isomer. However, these studies were made with different batches of synthetic pheromones, with different types of traps and according to different procedures, so the observed differences might not reflect true geographic variation. Here we investigate the geographic pattern of male sawfly response by using identical chemicals, traps and experimental procedures at eight field sites ranging from Japan in the east to Canada in the west. We found an increased inhibitory effect of the (2S,3R,7R)‐isomer from Japan and Siberia to Europe. At the eastern sites, increasing amounts of the (2S,3R,7R)‐isomer up to and equal to the amount of the (2S,3S,7S )‐isomer, did not influence the trap catch, whereas at sites in Europe, as little as 1% of the (2S,3R,7R)‐isomer almost completely inhibited the attraction. The response of the North American population was intermediate. The only site in which the (2S,3R,7R)‐isomer was essential for the attraction of males was in Siberia. A similar pattern was found for the (2S,3R,7S)‐isomer. Both the acetate and the propionate form of the (2S,3S,7S)‐isomer were attractive by themselves in Japan, Europe and North America, and neither the (2S,3R,7S)‐isomer nor the (2S,3R,7R)‐isomer alone were attractive, in the acetate or propionate form. We discuss the significance of our findings for the development of more efficient monitoring schemes and for the causes of population divergence and speciation in the European pine sawfly.

Mating disruption of the pine sawfly Neodiprion sertifer (Hymenoptera: Diprionidae) in isolated pine stands

1  Previous applications of the mating disruption technique to Neodiprion sertifer resulted in decreased numbers of males caught in the treated area but no effect on sex ratio or overall population density. 2  The present study assessed the efficacy of mating disruption against N. sertifer outbreaks in pine stands surrounded by agricultural areas or pasture, and therefore isolated from other infested areas. 3  Pine stands were treated by placing dispensers with an erythro‐mixture of the acetate ester of 3,7‐dimethyl‐2‐pentadecanol every 10 m in a grid. 4  The efficacy of this technique was evaluated by comparing the number of males caught in sticky traps baited with synthetic pheromone, and by comparing the sex ratio and the population density of the sawfly in the subsequent generation between treated and control pine stands. 5  The number of males caught within treated areas was significantly lower than in the control area. 6  In the treated pine stands 46% of the egg clusters resulted in male cocoons only, compared to 3% of the clusters in the control stand. 7  A significant reduction of the sawfly population was observed in the treated pine stands. The results contrast to the earlier mating disruption attempts with N. sertifer and can probably be ascribed to the isolation of the experimental stands.