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.

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.

The laboratory rearing of Neodiprion sertifer (Geoffroy) on Pinus sylvestris L. plants grown in vases was successfully achieved on a continuous basis. Larvae were seen to emerge on average after 106 days from egg clusters being kept on plants held at a temperature of 15±1°C and with a 10-h photophase until emergence. These larvae were then transferred to plastic containers and kept at a temperature of 20±1°C with a 12-h photophase where, under optimum hygiene conditions and being fed fresh pine branches, they completed their development on average in 30.6 days. Adults began emerging from the cocoons after about 30 days, continuing to do so for at least 7 months. Under these conditions the insect completes its life cycle in 179 days, thus permitting to obtain two generations a year in the laboratory. This staggered adult emergence pattern makes specimens available at all stages of development for experimental purposes throughout most of the year.

Juvenoids could be a useful tool for the control of psyllids. The 12 new juvenoids synthetized at the Institute of Organic Chemistry and Biochemistry in Prague were tested by dipping the feeding plants in the juvenoid solution and by indirect contact application on Cacopsylla (Psylla) pyri (L.). The tested compounds were mostly less active than the commercial juvenoid, methoprene. However, even the low doses of active juvenoids which evoked only small malformations on wings and external genitalia of the treated psyllids disabled them from flying and also from copulation. The most sensitive period for juvenoids in psyllids comprises the first 4 days of the last larval instar. Aside from this period, juvenoids failed to evoke any malformation. The investigated juvenoids were also tested on the main predator of psyllids, the pirate bug, Anthocoris nemoralis (Fabr.), using the indirect topical application. It was found that the sensitive period of these bugs to the tested juvenoids is restricted to the first 24 h of the last larval instar. Hence, the pirate bug revealed very low sensitivity to the tested juvenoids.