Structure-activity relationships for analogs of (+)-(E)-endo-beta-bergamoten-12-oic acid, an oviposition stimulant of Helicoverpa zea (Boddie)

beta-Bergamotenoic acid, a compound previously shown to stimulate oviposition in H. zea, was converted into a set of bicyclic analogs and tested with a set of acyclic side chain analogs to ascertain the molecular structure that maximizes insect behavioral response. While changes in the bicyclic ring elicited no variation in response, alteration in the side chain structure of beta-bergamotenoic acid resulted in significant changes in moth preference. Free rotation about the C-C bond proximal to the carboxylic acid group appears to be an important structural factor, since saturation of the side chain double bond significantly increased activity. The carboxylic acid group seems to be required for strong oviposition stimulation, since analogs lacking the carboxylic acid group exhibited no significant oviposition activity. Oviposition preference of H. zea was also influenced by the length of the hydrocarbon chain to which the carboxylic acid is attached. While hexanoic acid was found inactive, the ovipositional preference for the heptanoic and octanoic acids was greatest for the one 8-carbon tested. This and other work suggest that carboxylic acids of specific chain lengths influence the oviposition behavior of both Helicoverpa and Heliothis species and may be associated with host-plant selection. The potential use of this information in designing integrated pest management strategies for control of H. zea is discussed