Evaluation of mating disruption systems for navel orangeworm in California almonds

Abstract: Mating disruption is a key element of integrated pest management programs for
navel orangeworm in California almonds. Between 2019 and 2021 we used 88 unique 16-ha
almond orchards to evaluate six different mating disruption systems that disseminate
pheromone using pressurized aerosol cans, passive meso dispensers, and applications of
microencapsulated formulations to the foliage. Aerosol-based products caused significant
pheromone trap shutdown of > 95 %, reduced egg trap captures by 69-72 % across the four
navel orangeworm flights, and reduced damage to the varieties Nonpareil and Monterey by
58.4 % and 51.8 %, respectively. Meso emitters likewise reduced pheromone trap captures by
a season-long average of 88 %, reduced egg captures by 34 % to 58 % across the four flights,
and reduced damage by 22.0 % in Nonpareil and 31.8 % in Monterey. Applications of sprayable formulations of pheromone, regardless of whether they were applied four or two times during the season, failed to reduce pheromone trap captures by more than 60 % and had no impact on the number of eggs or damage levels at harvest. The dissemination of these results to nut crop producers in California has helped contribute to more than 160,000 ha of mating disruption adoption by almond, pistachio and walnut growers statewide.