Field observations quantifying attraction of four tortricid moths to high-dosage pheromone dispensers in untreated and pheromone-treated orchards

Orientational responses of four species of feral tortricid moths (Lepidoptera: Tortricidae) to polyethylene tube dispensers of pheromone were observed in a 0.8 ha apple orchard treated with such pheromone dispensers and in an untreated 0.8 ha orchard. Male oblique-banded leafrollers, Choristoneura rosaceana (Walker) (mean 7.2 +/- 0.4 moths/night during 21 nights), Oriental fruit moths, Grapholita molesta (Busck) (mean 10.5 +/- 2.1 during 20 evenings), and the redbanded leafrollers, Argyrotaenia velutinana (Walker) (mean 2.0 +/- 1.1 during 14 nights) were observed approaching within 100 cm of their respective polyethylene-tube pheromone dispensers in the untreated orchard. Furthermore, C. rosaceana (mean 2.0 +/- 0.7 during 17 nights) and G. molesta (mean 1.5 +/- 0.4 over 20 evenings) came within 100 cm of their respective polyethylene-tube pheromone dispensers in the pheromone-treated orchard. Most visits lasted less than 10 s, after which the majority of moths departed by flying upwind. In the untreated orchard, the number of C. rosaceana observed orienting to polyethylene tube dispensers was greater than the number captured in optimized monitoring traps (1.9 +/- 0.4) per night of observation. The numbers of A. velutinana (2.0 +/- 1.1) or G. molesta (10.5 +/- 2.1) attracted to polyethylene-tube dispensers in the untreated orchard did not differ statistically from the numbers captured in optimized monitoring traps per night of observation. In the pheromone-treated orchard, the number of C. rosaceana (2.0 +/- 0.4) or G. molesta (1.2 +/- 0.2) observed orienting to polyethylene-tube dispensers did not differ statistically from the numbers of male moths of these species captured in optimized monitoring traps per night of observation. No codling moths, Cydia pomonella L. were observed orienting to, or landing near, their respective polyethylene-tube dispensers in either the untreated or pheromone-treated orchards, although substantial numbers were captured in monitoring traps per night of observation (6.0 +/- 1.7) in the untreated orchard. The attraction of male moths to polyethylene tube dispensers thus occurred in three of the four species observed. These results provide support for the idea that false-plume-following is an important component of the mechanisms mediating communicational disruption in moths by polyethylene-tube dispensers.