Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/16/2012
Publication Date: 4/1/2012
Citation: Higbee, B., Siegel, J.P. 2012. Field Efficacy and application timing of methoxyfenozide, a reduced risk treatment for control of navel orangeworm (Lepidpotera: Pyralidae) in almonds. Journal of Economic Entomology. 105(5):1702-1711. Interpretive Summary: The navel orangeworm, Amyelois transitella, is the primary lepidopteran moth pest of almonds, although there are other moths, such as Peach twig borer, Anarisia lineatella and Oriental fruit moth, Grapholita molesta, that can also be important pests of almonds. In our two year field study navel orangeworm accounted for more than 60% of the moth damage. We evaluated the impact of a new reduced risk insecticide that interferes with proper molting, Intrepid (methoxyfenozide), on navel orangeworm and these other moth pests and contrasted its efficacy with the efficacy of broad spectrum insecticides belonging to the organophosphate (Phosmet) and pyrethroid (permethrin) classes. This study also investigated several treatment timings, a single hull split spray, spring spray and hull split spray, and pre and post hull split sprays in order to determine if one was more effective than the others. In our study Intrepid was as effective or in some cases more effective than the broad spectrum insecticides, thereby validating its use in almonds. Several sprays of Intrepid were more effective at reducing damage than a single spray. The greatest reduction in damage occurred when the spring spray was combined with sprays bracketing hull split in almonds. Springtime is the traditional time to spray almonds to reduce damage from peach twig borer, and since Intrepid also is effective against peach twig borer a spring spray has the potential to reduce the population of both pests. We conducted additional studies demonstrating that Intrepid is very toxic to navel orangeworm eggs, and the susceptibility of these eggs has implications for control. Early application of Intrepid at the initiation of hull split will produce the greatest control because the eggs will be killed before the larvae enter the nut. Continued research is necessary to optimize insecticide timing and maximize damage reduction.
Technical Abstract: 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’ variety almonds located in Kern County, California. Methoxyfenozide applied one to three times, and the organophosphate phosmet (Imidan®), alone or in combination with the pyrethroid permethrin (Perm-Up®), were tested for efficacy against the primary lepidopteran pest, navel orangeworm Amyelois transitella (Walker) and three other lepidopteran pests of almond, oriental fruit moth Grapholita molesta (Busck), obliquebanded 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 post-hull split application was as effective as the applications bracketing hull split. Navel orangeworm accounted for more than 60% of the total damage, while 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.