Field efficacy and application timing of methoxyfenozide, a reduced-risk treatment for control of navel orangeworm (Lepidoptera: Pyralidae) in almond.

Large-scale field efficacy trials of methoxyfenozide (Intrepid), a reduced-risk molting agonist insecticide, were conducted in 2004 and 2005 in an orchard containing 'Nonpareil' and 'Sonora almonds [Prunus dulcis (Mill.) D.A. Webb] located in Kern County, CA. Methoxyfenozide applied one to three times, the organophosphate phosmet (Imidan) alone or in combination with methoxyfenozide, or the pyrethroid permethrin (Perm-Up) were tested for efficacy against the primary lepidopteran pest navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), and three other lepidopteran pests of almond: oriental fruit moth, Grapholita molesta (Busck); oblique-banded leafroller, Choristoneura rosaceana (Harris); and peach twig borer, Anarsia lineatella Zeller. Two or three applications of methoxyfenozide (bracketing hull split or spring plus bracketing hull split) were more effective than a single hull split application of phosmet, phosmet combined with permethrin, or methoxyfenozide. In these trials, a spring application followed by a posthull split application was as effective as the applications bracketing hull split. Navel orangeworm accounted for > 60% of the total damage, whereas oriental fruit moth and peach twig borer were the dominant secondary pests. In experiments conducted in 2010 to assess the direct toxicity of methoxyfenozide to navel orangeworm eggs under field conditions, exposure to methoxyfenozide reduced survival by 96-99%. We conclude that this reduced-risk insecticide is effective, although its efficacy is maximized with more than one well-timed application.