Behavioral and neurosensory responses of the boll weevil, Anthonomus grandis Boh. (Coleoptera: Curculionidae), to fluorinated analogs of aldehyde components of its pheromone

Competitive field tests with alpha-fluorinated analogs of compounds III and IV (III-alpha-F and IV-alpha-F, respectively) of the boll weevil, Anthonomus grandis Boh., aggregation pheromone showed these compounds, when combined with the other pheromone components [(+/-)-I and II], to be as attractive as grandlure [(+/-)-I, II, and III + IV]. Dose-response curves constructed from electroantennograms of male boll weevils to serial stimulus loads of III, IV, III-alpha-F, IV-alpha-F, and the corresponding acyl fluorinated analogs (III-acyl-F and IV-acyl-F) showed the alpha-fluorinated analogs to be as active as the pheromone components (threshold = 0.1 micrograms), while the acyl fluorinated analogs had a 10-100 X higher threshold (= 1-10 micrograms). Single-neuron recordings showed that IV neurons and II neurons (Dickens, 1990) responded to IV-alpha-F and III-alpha-F, respectively, while IV-acyl-F and III-acyl-F were inactive. Since a previous study showed compounds I, II, and IV to be essential for behavioral responses in the field, it seems likely that the activity of the alpha-fluorinated analogs observed here is due to the stimulation of IV neurons by IV-alpha-F as indicated in single neuron recordings