Mechanisms of pheromone communication disruption in Choristoneura rosaceana exposed to microencapsulated (Z)-11-tetradecenyl acetate formulated with and without horticultural oil.

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.