Development of an attractant for the scarab pest Macrodactylus subspinosus (Coleoptera: Scarabaeidae).

Field trials were conducted over several seasons to determine the attractant most successful in luring adult rose chafers, Macrodactylus subspinosus (F.), to traps. During the first season, 20 compounds were compared with the standard lure, valeric acid + hexanoic acid + octyl butyrate (1:1:1). The two new standards establishedthat season were: valeric acid + 1-nonanol (1:1); and valeric acid + hexanoic acid + octyl butyrate + 1-nonanol (1:1:1:1). The following season, 36 compounds were evaluated, comparing them to the new standards. The performance of the standard binary lure valeric acid + 1-nonanol was improved when the alcohol 1-nonanol was replaced by its analog trans-2-nonenol and this was confirmed during the third season. At the same time, a second test was conducted with 29 new candidates, which were combined with valeric acid and compared with the standard: valeric acid + hexanoic acid + octyl butyrate + 1-nonanol (1:1:1:1). A control and the single compound alpha-ionone were included, resulting in the discovery of a new more powerful attractant, alpha-ionone. Testing of alpha-ionone continued the following season, at which time the initial leading candidate and new ones containing trans-2-nonenol were tested against the single attractant alpha-ionone and various combinations of it. A new five-component mixture of valeric acid, hexanoic acid, octyl butyrate, trans-2-nonenol, and alpha-ionone out performed all other lure combinations.