Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Residues and routes of exposure of insecticides in turfgrass for control of fall armyworm larvae (Lepidoptera: Noctuidae).

Abstract

Fall armyworm, Spodoptera frugiperda (J.E. Smith), is a generalist pest of food crops and turfgrasses. Insecticides such as diamides provide longer residual control of some grass-feeding caterpillars relative to pyrethroids. The objective was to compare the responses of fall armyworm larvae to residues of commonly used insecticides on hybrid bermudagrass (Cynodon dactylon (L.) × C. transvaalensis Burtt-Davy). A field experiment determined mortality of free-ranging fall armyworms exposed for 1-3 h on turfgrass at 1, 7, 14, 28, and 42 d after a foliar application. A laboratory experiment determined the mortality of larvae fed grass clippings harvested from treated plots at 1, 3, 7, 14, 28, and 42 d after application. Larvae crawled similar or greater distances across bermudagrass treated with bifenthrin and permethrin relative to nontreated grasses. After crawling on bermudagrass treated with chlorantraniliprole or cyantraniliprole 14 d after application, larval mortality was ≥77%. Mortality of larvae fed pyrethroid-treated clippings was ≤40% and no different from control larvae regardless of residue age. Larvae fed bermudagrass with 1 to 7 d old residues of cyantraniliprole or indoxacarb resulted in significantly greater mortality than larvae fed nontreated clippings. No residues of cyantraniliprole or indoxacarb older than 7 d resulted in mortality significantly greater than larvae fed nontreated clippings. Larvae fed chlorantraniliprole-treated clippings of all residue ages produced larval mortality greater than larvae fed nontreated clippings. These experiments support previous reports of extended residual control from chlorantraniliprole against other grass-feeding caterpillar species. The diamides protect turfgrass from larvae better than pyrethroids.