Different concentrations of nuclear polyhedrosis virus were applied as aqueous suspensions using a tractor mounted or a backpack-manual sprayer to control Spodoptera frugiperda (Smith) larvae on maize (Zea mays L.). Larval mortality varied with the application equipment. For the tractor-mounted sprayer application of at least 2.5 x 10(12) P.I.B./ha was necessary to attain a control comparable to that obtained with the backpack-manual sprayer application (70.2%). For this application method it can be used the dose of 2.5 x 10(11) PI.B./ ha, butNPV persistence was very short. A greaterNPV persistence was obtained with doses over 1.25 x 10(12) P.I.B./ha (93.4% mortality). The occurrence of parasitoids in the experimental area increased larval mortality rate (16.4%), independent of the application method. Among the parasitoids, the most prevalent was Campoletis flavicincta (Ashmead) (53.0%), followed by Chelonus insularis (Cresson) (31.3%), and Eiphosoma spp. (15.6%).
Insecta; fall armyworm; Baculovirus; biological control
