Pheromone released from polyvinyl chloride dispensers disrupts mate-finding and pheromone-source location by Rhopobota naevana (Lepidoptera: Tortricidae) in cranberries

Blackheaded fireworm (Rhopobota naevana (Hbn.)) mating can be disrupted by pheromone components released from spiral polyvinyl chloride (PVC) dispensers in large field plots on cranberry (Vaccinium macrocarpon (Aiton) (Ericaceae)) farms. The main pheromone component ((Z)-11-tetradecen-1-ol acetate (Z11-14:Ac)) or a blend similar to natural pheromone (Z11-14:Ac, (Z)-11-tetradecen-1-ol (Z11-14:OH), and (Z)-9-dodecen-1-ol acetate (Z9-12:Ac)) was released from PVC dispensers into 0.8-ha plots on cranberry farms. Regardless of the treatment, free-flying males in treatment plots located fewer than 5% of individually caged virgin females, whereas mate location in most control plots ranged from 14%–75%. Location of pheromone lures loaded with 1.0 mg of the three-component blend was reduced in both treatments, but not to the same extent as was location of females. The magnitude of mating disruption indicated by 0.01-mg lures was similar to that indicated by caged females. Estimated release rates from dispensers loaded with Z11-14:Ac alone were linear and similar in both years of the study, declining from 575–720 mg/ha per day to 175–220 mg/ha per day after 100 days. Three-component dispensers placed in the field in July 1994 showed a steeper decline in release rates of Z11-14:Ac and a change in component ratios from 6.2:2.5:1 to 8:2:1 (Z11-14:Ac: Z11-14:OH: Z9-12:Ac) over the 60-day release period. After one season of mating disruption, the number of eggs and the number of foliar samples with larval feeding shelters were not consistently reduced in treatment plots. Mated females may have dispersed into the plots and oviposited. PVC dispensers effectively disseminate pheromone for mating disruption but are labor-intensive to use. In the cranberry system, their use might be limited to research plots and isolated farms of <8 ha.