3.6 Behavioral bioassays
Male ECB moths responded with approach and landing to 50 μg of the pheromone blend corresponding to the Z -race (Figure 5B). As BioPhe contains just 7.2% Z 11-14:OAc, a 700 μg stimulus of BioPhe was tested in lab bioassays (containing approx. 50 μgZ 11-14:OAc). Significantly fewer source-oriented approaches and fewer landings were observed compared to the response elicited by the optimal Z-race pheromone, indicating the presence of compound(s) interfering with the insects’ anticipated behavior.
In the BioPhe sample 14:OAc comprises almost 50% of the total amount. To emulate a BioPhe sample, 350 μg 14:OAc were added to the 50 μg pheromone blend (97:3). In this case, males scored significantly lower in both approach and landing. This is an indication that 14:OAc at this dose interferes with the precopulatory behavior of O. nubilalis.
Similarly, when 4.5 μg of Z 9-16:OAc was added to the 50 μg pheromone blend (97:3), significantly fewer landings were recorded, but the frequency of approaches did not differ significantly from what was observed in response to the native pheromone .