FIELD ELECTROANTENNOGRAM AND BEHAVIORAL-RESPONSES OF EPIPHYAS-POSTVITTANA (LEPIDOPTERA, TORTRICIDAE) UNDER LOW PHEROMONE AND INHIBITOR CONCENTRATIONS

Mating disruption of Epiphyas postvittana (Walker) was studied in two 0.1-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 b lend of pheromone (54.9 mg [E]-11-tetradecenyl acetate and 2.5 mg of [ E,B]-9,11-tetradecadienyl acetate) and inhibitor (19.7 mg of [Z]-11-te tradecenyl acetate). The incidence of mating of tethered females place d in treated or untreated plots significantly increased with the incre ased numbers of males released. Mating was reduced with estimated pher omone release rates from dusk from 1.1-4.4 mg/ha/h. In the control plo ts, trap catch (mean+/-SEM) over 173 d was 0.207+/-0.074 males per tra p 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 p lots and 0.001 + 0.001 males per trap per day in the 200-dispensers-pe r-hectare plots. No moths were caught at 400-dispensers-per-ha level. Mating frequency averaged 12.9% of the control level at 173 d after tr eatment, 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. P heromone 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 distinguis hable above the orchard background volatiles. However, the standard er ror of electroantennogram responses was negatively correlated with rel ease rate. Time series of continuous electroantennogram recordings ove r 30-60 s also showed significant differences in root mean square of t he signal between treated and untreated plots after 4 mo, with higher variance in the samples taken above grass rows.