Pests are a threat to agricultural production. Botanically based insecticides can cause less acute and chronic risk to human health and the environment while controlling, repelling, and/or modifying insect pest behavior to mitigate damage to the human-valued resource. Botanicals can be a management option to reduce reliance on use of synthetic insecticide. Efficacies of botanical powders of rue (Ruta graveolens L.), creosote bush (Larrea tridentata (Sessé & Moc. Ex DC.) Coville), and dense mistletoe (Phoradendron densum Torr. ex Trel.) were evaluated against first-instar larvae of fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), in a laboratory. Fifteen replications were used of dehydrated, powdered, plant foliage from the three plant species at six concentrations of 0.03, 0.06, 0.12, 0.24, 0.48, and 0.96 g and a nontreated check mixed with 12 g of artificial diet. The number of armyworms dead at 10 days after exposure and instar development every 24 hours were recorded. At 10 days, significant numbers of armyworms were killed by all plant powders. Development of S. frugiperda varied with the plant species and concentration: P. densum and L. tridentata were effective at all concentrations against larvae. P. densum was effective in preventing adult eclosion, although at 0.03 g, 6.7% of the larvae developed to the pupal stage. Non treated fall armyworms of the check completed the life cycle. Creosote bush, rue, and dense mistletoe botanical powders were promising alternatives for managing fall armyworm without insecticide.