Mating Disruption of the Navel Orangeworm (Lepidoptera: Pyralidae) Using Widely Spaced, Aerosol Dispensers: Is the Pheromone Blend the Most Efficacious Disruptant?

The navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), is a key pest of almonds and pistachios and is sometimes controlled using mating disruption as part of a program of integrated management. The formulation used has a single, nonattractive compound [(11Z,13Z)-hexadecadienal] as the active ingredient that is emitted from timed aerosol dispensers. This study compared this nonattractive, single-compound formulation with two aerosol formulations also containing two additional compounds [(11Z,13Z)-hexadecadien-1-ol and (3Z,6Z,9Z,12Z,15Z)-tricosapentaene] that are found in the pheromone glands, and that in combination with the aldehyde are attractive in wind-tunnel and field-attraction trials. An experiment in pistachios found 97% to 99% suppression of males captured in female-baited traps and 82-93% suppression of mating in sentinel females. Both assays revealed a trend to greater suppression by the more complete pheromone formulations. In almonds, where the abundance of navel orangeworm was lower, all three formulations suppressed males captured in traps and mating in sentinel females by >99%. Each of the formulations significantly reduced damage to Nonpareil almonds. In almonds, there were no significant differences among the formulations in disruption of sexual communication or in damage. These findings suggest that it may be possible to make mating disruption more cost-effective and to achieve higher levels of mating disruption by using attractive aerosol formulations to reduce the number of dispenser per ha. Such a formulation, however, would be more expensive to register in the United States than pheromones meeting the definition of straight-chain lepidopteran pheromone, including the currently used aldehyde-only formulation.