The effects of the horticultural oil Purespray Green on oviposition behaviour and egg development in the obliquebanded leafroller, Choristoneura rosaceana (Harris), were investigated through dual-choice and no-choice bioassays and topical applications of oil to developing eggs. A residual 2% (v/v) oil spray on wax-paper and apple-leaf substrates significantly reduced both the number of eggs laid and egg survival in no-choice assays; however, this effect diminished 3 days after treatment. In dual-choice assays, females laid significantly fewer eggs on oil-treated apple leaves than on control leaves, but laid equal numbers of eggs on the oil-treated wax paper and the untreated wax-paper controls. Topical application of oil caused significant dose-dependent mortality of both newly laid eggs and eggs just before hatch, and these two egg stages were equally susceptible to the oil. Topical application of 2% oil caused >99% egg mortality. Our data indicate that gravid female C. rosaceana can assess and reject oil-sprayed surfaces and that the oil can kill eggs through both contact toxicity and suffocation. These characteristics suggest that highly purified horticultural oils like Purespray Green could play a role in an integrated pest management program for this important pest species.

Flight tunnel and electrophysiological assays with male Choristoneura rosaceana Harris (Lepidoptera: Tortricidae) were conducted to investigate the non-competitive mechanisms of communication disruption caused by microencapsulated (MEC) (Z)-11-tetradecenyl acetate (3M MEC-LR) formulated with and without horticultural oil (Purespray Green). Male C. rosaceana were exposed for 1 h by resting on metal surfaces sprayed with either water, 2% oil in water, MEC-LR in water, or MEC-LR + 2% oil in water. In one experiment, sprayed surfaces were allowed to age up to 47 days in a laboratory fume hood prior to moth exposure to examine the effect of ageing on the disruptive efficacy of the formulations. In flight tunnel assays with calling females, males exposed to MEC or MEC + oil treatments for 1 h were significantly disrupted up to 1 h after exposure, and both treatments were effective for 47 days. Electroantennograms revealed no reduction in antennal sensitivity when measured 75 s after a 1-h exposure. Collectively, these results support habituation as a key mechanism of communication disruption for C. rosaceana exposed to the MEC formulations tested here. Male proximity to the pheromone-treated surfaces appears to be important in maintaining a disruptive effect as MEC treatments age and pheromone release rates decline. The addition of 2% oil increased the number of microcapsules deposited on sprayed surfaces and caused a moderate but significant increase in the disruptive effect of the MEC formulation. A better understanding of the mechanisms that underlie disruption by MEC formulations, and how an adjuvant like horticultural oil may enhance these mechanisms, may lead to improvements in this technology.

Sprayable, microencapsulated (MEC) sex pheromone formulations represent a promising tool for achieving mating disruption, yet often lack sustained effectiveness in the field, making repeated applications necessary. This study evaluated the impact of adding Purespray Green horticultural oil as an adjuvant to 3M MEC-LR, an MEC formulation of (Z)-11-tetradecenyl acetate, on disruption of mate-finding behavior in Choristoneura rosaceana (Harris) in small-plot trials in experimental apple orchards. Treatments consisting of MEC-LR in water, MEC-LR in water + 2% (vol:vol) Purespray Green, and a water control were applied to plots of apple using an airblast sprayer at a rate of 100 g of pheromone/ha. Disruption caused by foliar treatments was evaluated over a 7-wk period using mark-release recapture experiments in the field and concurrent bioassays in a flight tunnel. Disruption of orientation to 2-d-old, calling, virgin females was used as a measure of treatment effect in all experiments. Both pheromone alone and pheromone + oil treatments significantly disrupted male mate-finding behavior for a period of > or =21 d in flight tunnel assays and > or =42 d in mark-recapture field trials. The addition of oil did not significantly enhance the disruption activity nor increase the longevity of the MEC pheromone formulation. Our results show the compatibility of spraying MEC pheromone with a horticultural oil, and techniques for applying an oil-pheromone formulation to maximize the control impact of this combination are discussed.