Field Electroantennogram and Behavioral Responses of Epiphyas postvittana (Lepidoptera: Tortricidae) Under Low Pheromone and Inhibitor Concentrations

Abstract

Mating disruption of Epiphyas postvittana (Walker) was studied in two O.l-ha plots at a 10.6-ha apple orchard each with either 0, 100,200, or 400 dispensers per hectare; the dispensers released an attractive blend of pheromone (54.9 mg [E]-ll-tetradecenyl acetate and 2.5 mg of [E, EI-9, 11-tetradecadienyl acetate) and inhibitor (19.7 mg of [Z]-ll-tetradecenyl acetate). The incidence of mating of tethered females placed in treated or untreated plots Significantly increased with the increased numbers of males released. Mating was reduced with estimated pheromone release rates at dusk from 1.1-4.4 mg/ha/h. In the control plots, trap catch (mean ± SEM) over 173 d was 0.207 ± 0.074 males per trap per day. In the pheromone and inhibitor treatments, 0.004 ± 0.003 males per trap per day were caught in the 100-dispensers-per-hectare plots and 0.001 ± 0.001 males per trap per day in the 200-dispensers-per-hectare plots. No moths were caught at 400-dispensersperha level. Mating frequency averaged 12.9% of the control level at 173 d after treatment, with release rates from 0.15-0.51 mg/ha/h. Electroantennogram signals recorded in treated apple-orchard plots showed a significant effect from increasing the rate of dispenser application after 83 d. Pheromone and inhibitor levels had higher variance in the grass between rows of trees than within the tree rows. By 140 d after treatment, no electroantennogram response to pheromone and inhibitor was distinguishable above the orchard background volatiles. However, the standard error of electroantennogram responses was negatively correlated with release rate. Time series of continuous electroantennogram recordings over 30-60 s also showed significant differences in root mean square of the signal between treated and untreated plots after 4 mo, with higher variance in the samples taken above grass rows.