(3<i>Z</i>,6<i>Z</i>,9<i>Z</i>,12<i>Z</i>,15<i>Z</i>)‐pentacosapentaene and (9<i>Z</i>,11<i>E</i>)‐tetradecadienyl acetate: sex pheromone of the spruce coneworm <i>Dioryctria abietella</i> (Lepidoptera: Pyralidae)

Abstract

Abstract The spruce coneworm, Dioryctria abietella Denis &amp; Schiffermüller (Lepidoptera: Pyralidae), is a major pest in spruce seed orchards in Europe. Initial work on its pheromone ecology reported significant attraction of males to (9 Z ,11 E )‐tetradecadienyl acetate (9 Z ,11 E ‐14:OAc), but this compound appeared to be a very weak attractant in field trials. In this study, we show that a second female‐produced compound, the polyunsaturated long‐chain hydrocarbon (3 Z ,6 Z ,9 Z ,12 Z ,15 Z )‐pentacosapentaene (C25 pentaene), is a strong synergist to 9 Z ,11 E ‐14:OAc, and that both compounds are needed for significant attraction of males. In field‐trapping experiments, the highest catches were obtained with high amounts of pentaene added to the acetate (acetate:pentaene ratio from 1 : 10 to 1 : 30) and the highest doses (1–3 mg per rubber septum dispenser) were the most attractive. Two potential behavioural synergists, ( Z )‐9‐tetradecenyl acetate and (9 Z ,12 E )‐tetradecadienyl acetate, turned out to be behavioural antagonists and both reduced trap catch of D. abietella in a dose‐dependent way when added individually to the binary blend. The recent discovery of the C25 pentaene as a pheromone component of D. abietella , as well as of three North American congeners, suggests that the use of a mixture of so‐called type I and type II pheromone compounds is a widespread motif of sexual communication within the genus. The identification of a highly attractive sex pheromone will help in developing efficient strategies for monitoring and control of D. abietella populations in European spruce seed orchards.