Catches of Euxoa tritici in pheromone traps for Anarsia lineatella are due to the presence of (Z)‐5‐decenyl acetate as an impurity.

Traps baited with the synthetic pheromone of Anarsia lineatella Zeller (Lepidoptera: Gelechiidae) frequently captured also Euxoa tritici L. males (Lepidoptera: Noctuidae) in field tests in Hungary. As (E)‐monounsaturated compounds are uncommon among sex attractants or pheromone components of Noctuidae, it was hypothesized that the Euxoa catches may have been due to impurities of the (Z) isomer in synthetic (E)‐5‐decenyl acetate, which is the major component in the pheromone lure of A. lineatella. Traps baited with synthetic (Z)‐5‐decenyl acetate captured large numbers of E. tritici, and the compound showed a clear dose–response effect. Reanalysis of the synthetic batch of (E)‐5‐decenyl acetate used in preparation of the A. lineatella lure showed the presence of 10% of the (Z) isomer. Traps baited with synthetic (Z)‐5‐decenyl acetate can be used in the future for detection and monitoring purposes of E. tritici, a widely distributed pest of cereals and other field crops. The compound also showed attraction of Euxoa seliginis Duponchel. [ABSTRACT FROM AUTHOR]