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Are you Getting
Residual Control of Fall Armyworms
from your Insecticide Applications? By Elijah Carroll, Kendra Carson and Dr. David Held
Al ab ama Tu rf Tim e s > >> Su mmer 201 9
T
he fall armyworm (Spodoptera frugiperda), is a significant pest of all turf and pasture grasses throughout the eastern United States. There are several species of armyworms in our area, but this species develops faster (21 days from egg to adult) than the others and has 4–5 generations a year in Alabama. Fall armyworms have a white wishbone on the head and four distinct dots on the end abdominal segment. They do not overwinter in Alabama; however, moths arrive every spring from southern TX and FL and have continuous generations through fall. Outbreaks of fall armyworms are most common in mid to late summer. By then, multiple generations are overlapping leading to large populations that cause significant damage. Fall armyworms feed in large numbers and, in urban lawns, these masses of larvae can easily scalp a lawn in a day. Despite their small size, they can move between lawns in a typical subdivision, between fields, or from rough to fairway in a short time. The fast generation time, movement and feeding behavior of fall armyworms means that once or twice a year, turf managers must decide how best to respond to fall armyworm damage. For example, do I use a short residual (and less expensive) insecticide, or do I treat with longer residual insecticides as ‘insurance’ against future outbreaks? Newer insecticides have been marketed for extended residual control. Two anthranilic diamides, chlorantraniliprole (Acelepryn) and cyantraniliprole (Ference), are noted for having longer residuals in turfgrass relative to synthetic pyrethroids. Anthranilic diamides are effective by contact and ingestion.
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However, our literature review only found two papers concerning residual control of turf-infesting caterpillars with either of these products. One study (Williamson et al. 2013, Int. Turf. Res. Soc. J, 12:1-5) found significant mortality of caged black cutworm larvae on creeping bentgrass treated 88 days prior to exposure with chlorantraniliprole. Another study reported significant mortality of tropical sod webworms on a St. Augustine grass lawn treated 5 weeks prior to exposure with chlorantraniliprole (Tofangsazi et al. 2015, J. Econ Entomol, 108:730735). These studies support the claims of long residual control made in the technical bulletins for these products. However, neither study investigated fall armyworms, or differences in toxicity if larvae were exposured by contact, or consumption, of treated grass. Our study addressed these two questions using fall armyworms in short-mown hybrid bermudagrass. This study was conducted at the Turfgrass Research Unit at Auburn University from late July to late September using two experiments to determine exposure by contact or ingestion. One field experiment determined the contact exposure of free-range fall armyworms on turfgrass at various times after treatment. Plots of Tifsport bermudagrass were treated with 7 insecticides (Triple Crown, Onyx Pro, Permetrol, Zylam, Provaunt, Acelepryn, and Ference) at label rates. These active ingredients represent synthetic pyrethroids in Onyx Pro and Permetrol; a neonicotinoid in Zylam; an oxadiazine in Provaunt; and diamides in both Acelepryn and Ference. Triple Crown is a mixed product containing both synthetic pyrethroids and a neonicotinoid. Twenty-four hours after
